Baneiie
Report
FATE AND BIOLOGICAL EFFECTS OF OIL WELL
DRILLING FLUIDS IN THE MARINE ENVIRONMENT
A LITERATURE REVIEW
U.S. ENVIRONMENTAL PROTECTION AGENCY
ENVIRONMENTAL RESEARCH LABORATORY
GULF BREEZE, FLORIDA 32561
September 9, 1981
arine Research Labo
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LIBRARY COPY
I K
FINAL
TECHNICAL REPORT
on
FATE AND BIOLOGICAL EFFECTS OF OIL WELL
DRILLING FLUIDS IN THE MARINE ENVIRONMENT:
A LITERATURE REVIEW
to
U.S. ENVIRONMENTAL PROTECTION AGENCY
ENVIRONMENTAL RESEARCH LABORATORY
GULF BREEZE, FLORIDA 32561
September 9, 1981
Report No. 15077
Prepared by
Jerry M. Neff, Ph.D.
Senior Research Scientist
BATTELLE
New England Marine Research Laboratory
Duxbury, Massachusetts 02332
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TABLE OF CONTENTS
Page
SUMMARY AND CONCLUSIONS.. .- 1
INTRODUCTION 6
DRILLING FLUID COMPOSITION AND USAGE 7
History
Functions 7
Drilling Mud-Handling System 10
Drilling Mud Composition 12
Dri 11 i ng Mud Programs 12
Trace. Metals in Drilling Muds. ; 22
Other Characteristics 31
FATE OF DRILLING FLUIDS DISCHARGED TO THE OCEAN 33
Di scharge Practi ces 33
Dispersion and Dilution in the Water Column 39
Deposition of Drilling Muds in Bottom Sediments 53
TOXICITY OF DRILLING FLUID COMPONENTS 63
Acute Toxicity 63
Chronic and Sublethal Effects 69
TOXICITY OF USED DRILLING FLUIDS TO MARINE ANIMALS 76
Bioassay Protocols 76
Acute Toxicity 79
Summary of Acute Bi oassay Resul ts 100
Chronic and Sublethal Effects...... 103
Microcosm Studies. 116
Interpretation of Bioassays in Relation to Field Observations....119
Field Studies 120
BIOAVAILABILITY OF HEAVY METALS FROM DRILLING MUDS 123
Laboratory Studi es 123
Fi el d Studi es 134
RECOMMENDATIONS 133
LITERATURE CITED 140
APPENDIX I
Drilling Mud Composition 1-1
APPENDIX II
Ongoing Research Programs on Effects of Used Drilling Muds on
Marine Animals II-l
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TABLE OF CONTENTS
/(continued)
LIST OF TABLES
Table 1
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Major chemical ingredients (annual consumption,
10,000 tons or more) of drilling muds, their major
trade names, and quantities and concentrations
used (From API, 1978)
Composition of drilling muds used at four depth
intervals to drill exploratory wells offshore in
the Canadian Arctic (Data from Bryant, 1976 and
Hrudey, 1979)
Time/depth history of drilling mud ingredients usage
during drilling of Mobil Oil Company's #1-76 well in
Mobile Bay, Alabama. Units are one thousand pounds
(Adapted from Jones, 1980).
Description of drilling mud ingredients used in Mobil
Oil Company's #1-76 well in Mobile Bay, Alabama.
Numbers refer to numbers in the mud component column
of Table 4 (From Jones, 1980)
Trace metal concentrations in drilling muds from
different sources. Concentrations are in mg/kg dry
weight (ppm)
Dissolved (aqueous phase) metal concentrations in
drilling mud samples taken at several depths from
the Imperial Oil Company, ADGO F-28 well offshore
the MacKenzie,'River Delta, Beaufort Sea, Canadian
Arctic. All values are in mg/liter (From Beak
Consul tants, 1974)
13
Amounts of drilling mud ingredients added to drill-
ing mud in different depth intervals during drilling
of an exploratory well in the Gulf of Mexico (Adapted
from Monaghan et al., 1977)
Concentrations of heavy metals in solution in seawater
equilibrated with solid barite (barium sulfate) contain-
ing low or high concentrations of trace metals. Concen-
trations are in yg/kg (parts per billion). (From Kramer
et al., 1980)
Summary of drilling mud discharges from an exploratory
drilling platform in Lower Cook Inlet, Alaska. Volumes
have been converted to gallons: according to 1 barrel =
42 gallons (From Houghton et al., 1980)
16
17
20
Trace metal composition of drilling fluid components,
Concentrations are in mg/kg dry weight (ppm)
21
23
25
28
30
. 36
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Table 11
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
TABLE OF CONTENTS
(continued)
Summary of drilling mud discharge plume data from
several metered drilling mud discharges from an
exploratory drilling platform on Tanner Bank off
Southern California. Heavy metals concentrations
are for the solid phase alone (From Ray and Meek,
1980)
Dilution and dispersion of two drilling mud plumes y
produced by high rate high volume discharges of used
chrome lignosulfonate drilling mud from an offshore
'exploratory platform in the Gulf of Mexico (From
Ayers et al., 1980b)
43
Acute toxicity of drilling fluid components to
estuarine and marine organisms
Acute toxicity of inorganic trivalent and hexavalent
chromium salts to marine animals
46
65
68
Numbers of animals and species collected from aquaria
containing sand alone or sand-barite mixtures and
receiving unfiltered natural seawater at a flow rate
of 200 ml/minute for 10 weeks (From Tagatz and Tobia,
1978; Tagatz et al., 1980)
71
Effects of biocides on recruitment from the plankton
of benthic macrofaunal invertebrates to sand substrata
in aquaria. Biocides were metered into inflowing water
to obtain concentrations indicated. (From Tagatz et al.,
1980) .\
Methods for preparation of drilling fluid bioassay
media according to recommendations of EPA, Region 2
(based on EPA/COE, 1977)
Methods for preparation of drilling fluid bioassay
media according to Neff et al., (1980, 1981)
74
77
78
Acute toxicity (measured as concentration killing
50 percent of test organisms in 96 hours, (96-hr. LC50)
of seven used Arctic drilling fluids to Arctic marine
fish and invertebrates. Whole drilling muds were used.
Values are in mg/ฃ (ppm) mud added initially (From
McLeay, 1975)
Composition of used drilling muds evaluated by Gerber
et al., (1980) and Neff et al. (1980, 1981)
80
82
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Table 21
Table 22.
Table 23.
Table 24.
Table 25.
Table 26.
Table 27.
TABLE OF CONTENTS
(continued)
Acute toxicity of the mud aqueous fraction (MAP)
of a used chrome lignosulfonate drilling mud to
several species and life stages of marine animals.
All 96-hour LC50 data are expressed as ppm mud
added (Data from Neff et al., 1981)
Page
83
Results of bioassays with five species of marine
invertebrates exposed to the suspended solids
phase (SSP) of a used chrome lignosulfonate drill-
'ing mud. Exposure concentrations are in mg miid/
liter of seawater (ppm). n.= number of animals per
treatment (From Neff et al., 1981)
Results of bioassays with five species of marine !
invertebrates exposed to the layered solid phase (LSP)
of a used chrome lignosulfonated drilling mud. Exposure
concentrations are in ml mud/liter seawater. n = number
of animals per treatment (From Neff et al., 1981)
Acute toxicity of the mud aqueous fraction (MAF) of
four used drilling muds to several species of marine
animals. All 96-hour LC50 values are expressed as ppm
mud added. Exposure media were changed daily during
bioassays (From Neff, 1980)
Acute toxicity, expressed as 96-hour LC50, of the mud
aqueous fraction (MAF) of five used offshore drilling
muds to cold-water species of marine animals from Maine.
All values are in ppm mud added (Data from Gerber et al.,
1980)....
Results of the bioassays on marine organisms exposed to
various fractions of used medium and light weight ligno-
sulfonate drilling mud and a spud mud. Unless specified
all animals are adults. MAF = mud aqueous fraction, WM =
whole mud substrate, WMW = washed whole mud substrate,
SSP = suspended solid phase, N = number of animals per
treatment. LC50 values are given as the ppm MAF, WM, WMW
or SSP. (From Gerber et al., 1981)
Toxicity of the suspended particulate phase (SPP) prepar-
ation of four used offshore drilling muds to adult coquina
clams Donax varidbilis texasiana, two size classes of spat
of the Pacific oyster Crassostrea gigas, and 1-, 5- and
10-day-old zoeae. of the grass shrimp Palaemonetes pugio.
Ninety-six-hour LC50 values are in ppm SPP preparation
added (Data from Neff, et al., 1980)
85
86
87
89
90
91
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TABLE OF CONTENTS
(continued)
Table 28.
Table 30.
Table 31.
Table 32.
Table 33.
Acute toxtcfty, expressed as 96-hour LC50, of the
layered solids phase preparation of four used off-
shore drilling muds to cold-water species of marine
animals from Maine. These were flow-through bioassays
with flow rates of 10-20 liters per hour. Values
are expressed as percent of whole mude in natural
marine substrate (From Gerber et al., 1980)
92
Table 29. Results of bioassays on six used drilling fluids ,
.typical of those used for exploratory drilling in
the mid-Atlantic OCS lease areas nos. 40 and 49. Mysid
shrimp Mysidopsis bakia were used for the liquid and
suspended particulate phase bioassays. The hard shell
clam Mercenaria mercenaria was used for solid phase
bioassays. Values for 96-hour LC50 in mysid bioassays
are in ppm mud added and in clam bioassays, results are
given in percent survival at 96 hours (From ERGO, Inc.,
1980).
Relationship between drilling mud type, well depth
and toxicity of whole drilling muds to Arctic marine
animals (From Tornberg et al., 1980)
97
Acute toxicity of a used high density ferrochrome :
lignosulfonate drilling mud to marine animals from
Cook Inlet, Alaska. LC50 values for whole mud bio-
assays are given in ppm mud added (From Houghton et al.,
1980a)
Toxicity to stage I larvae (less than 3 days old) of
shrimp and crabs of a used ferrochrome lignosulfonate !
drilling mud from Cook Inlet, Alaska. Toxicity was
measured by mortality (144 hr. LC50) and cessation of
swimming (144 hr. EC50). Bioassays were performed
with whole mud-in-seawater suspensions (SM) and
water-soluble fractions (WSF) of drilling mud. LC50,
EC50 concentrations and their 95% confidence intervals
are given in ppm mud added by volume (From Carls
and Rice, 1980)
Comparative acute toxicity of six Alaskan offshore
drilling muds to stage I larvae of king crab Para-
Hthodes comtsehatica and coonstripe shrimp Pandalus
hypsinotus. 144-hr. LC50 values for the drilling mud
water-soluble fractions are expressed as ppm mud added
'(Data from Carls and Rice, 1980) ,
98
99
101
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Table 34.
Table 36.
Table 37.
Table 38.
Table .39.
TABLE OF CONTENTS
(continued)
Characteristics of used drilling muds from different
depths of an exploratory drilling operation in Mobile
Bay, Alabama and acute toxicity (measured as percent
mortality at 96 hours at a nominal concentration of
1,000 ppm) of the whole muds to intermolt grass shrimp
Palaemonetes pugio (Data from Conklin et al., 1980;
Jones, 1980; Duke, personal communication)
...105
Table 35.'> Summary of the effects of the MAP of used seawater
chrome lignosulfonate drilling mild on the early life
history of Fundulus heteroclitus (From Neff, 1980)...
Shell growth rate (mm/10 days) of the ocean scallop,
Plaoopectin magellan-icus, exposed for 40 days to the
total suspended solids phase (SSP) of a medium-
density lignosulfonate drilling mud at 8.6 mg/fc in a
flow-through bioassay. Temperature increased from
5ฐC to 11.5ฐC over the exposure period. Each size
class was represented by six or seven scallops
(From Gerber et al., 1981)
109
.111
Enzyme activities in the sand shrimp Crangon septem-
spinosa, the green crab Carcinus maenus, and the
American lobster Homarus coneri.canus exposed for 96
hours for the mud aqueous fraction (MAF) of a used
light-density lignosulfonate drilling mud. Activity
units are mean values in 0.001/min/mg protein +; one
standard deviation; four to six animals were combined
for analysis. Values for exposure concentrations of
MAF are ppm mud added. AAT - aspartate aminotransferase;
G6PdH = glucose-6-phosphate dehydrogenase; BDL = below
detection limits; S = level of significance where
P = < 0.05, Student's t-test, values inside brackets
are not significantly different from controls (From
Gerber et al., 1980) 113
Enzyme activities* of the heart tissue of the northern
crab Cancer borealis exposed to the whole mud fraction
and the mud aqueous fraction of a medium-density ligno-
sulfonate mud for 96 hours at 5ฐC (From Gerber et al.,
1981)
114
Numbers of animals and species (mean no. per aquarium)
collected from aquaria containing sand alone or sand-
chrome lignosulfonate drilling mud mixtures and receiving.
unfiltered natural seawater at a flow rate of 200 ml/min
for 8 weeks (From Tagatz et al., 1978, 1980) 118
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Table 40.
Table 41
Table 42.
TABLE OF CONTENTS
(continued)
Accumulation of chromium by mussels Mytilus edulis
during exposure to chromium in different forms for
seven days (Data from Page et al., 1980)
127
Concentrations of several metals in four used drill-
ing muds as determined by flame atomic absorption
spectrophotometry. All concentrations are in mg metal/
kg dry mud (ppm), and standard deviation of two repli-
cate analyses. Values in parentheses are concentra-
tions determined by argon plasma emission spectrophoto-
metry (From McCulloch et al., 1980);
130
Bioaccumulation of chromium by the ocean scallop,
Plactopecten magellanicus, exposed for 40 days to the
suspended solids phase (SSP) and for 7 days to the
mud aqueous fraction (MAF) of a medium density ligno-
sulfonate drilling mud (From Gerber et al., 1981)
133
Figure .1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure .6.
LIST OF FIGURES
The drilling mud-handling system of a typical offshore
exploratory drilling rig (From Ray, 1979)
Relationship between drilling depth, drill cuttings
produced and time during exploratory drilling on Tanner
Bank, California (From Ray and Meek, 1980)..
Volumes of bulk drilling mud and cuttings discharges
each day during drilling of an exploratory well on Tanner
Bank, California (From Ray and Meek, 1980)
11
34
34
Daily and cumulative volume of solids control equipment
discharges (mainly cuttings and water) during explora-
tory drilling in the Baltimore Canyon off New Jersey
(From Ayers et al., 1980a).:..'
37
Daily and cumulative volume of total solids discharges
(bulk .mud discharges plus solids control equipment
discharges) during exploratory drilling in the Baltimore
Canyon off New Jersey (From Ayers et al., 1980a)
38
Idealized jet discharge described by mathematical model.
Cross-sections are shown at three stages of the plume.
A heavy class of particles is depicted settling out of
the plume at an early stage. Lighter particles are
shown settling during the collapse phase. Very fine
particles are shown leaving the plume shortly after
discharge and remaining near the surface to form the
visible plume. (From Brandsma et al., 1980)
41
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TABLE OF CONTENTS
(continued)
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Decline :in maximum total barium concentration in
drilling mud plumes with transport time (distance
from discharge/current speed) during two high-rate
bulk drilling mud discharges (From Ayers et al.,
1980b) .,
Decline in maximum total aluminum concentration (a
marker of the clay fraction) in drilling mud plumes
with transport time during two high-rate bulk
drilling mud discharges (From Ayers et al., 1980b).,
48
49
Decline in maximum total chromium concentration in
drilling mud plumes with transport time during two
high-rate bulk drilling mud discharges (From Ayers
et al., 1980b)
50
Relationship between bulk drilling mud discharge rate !
and transport time (distance from discharge/current
speed) required for solids concentration in the
drilling mud plume to reach background (From Ayers
et al., 1980b) .-". 51
Relative concentration of barium in bottom sediments
at different distances from four drilling rigs in
the northwestern Gulf of Mexico (From Ge'ttleson and
Lai rd, 1980)
Distribution of Mercury in the surficial Netserk
sediments (From Crippen et al., 1980).
56-
60
Accumulation of chromium by the marsh clam Rangia
cuneata during exposure to reference sediment from
San Antonio Bay, Texas (containing 20.36 mg Cr/kg
dry weight) and to a layered solid phase preparation
(LSP; 1:16 drilling mud: seawater) of used seawater
chrome lignosulfonate drilling mud (containing 485 mg
Cr/kg dry weight)' with or without a 24-hour period in
clean seawater after exposure. Vertical bars represent
standard errors of mean for 10 cl ams ........
129
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SUMMARY AND CONCLUSIONS
Drilling fluids or muds have a variety of functions integral to rotary
drilling for oil and gas. Drilling fluids are custom formulated to perform
these functions optimally under the unique conditions of each drilling opera-
tion. Therefore, no two drilling fluids are identical. Although there are
more than 1,000 trade name products and generic materials available for formu-
lating drilling fluids, 90 percent or more of the total ingredients of most ..
water-based muds used offshore in U.S. waters consists of four materials,
barite, bentonite clay, lignite and lignosulfonate.
During normal exploratory drilling operations, water-based drilling mud
may be discharged in small quantities with cuttings on a nearly continuous
basis. Larger bulk discharges of mud may take place several times during the
2 to 6 months usually required to drill a well and a few times at the end
of drilling. The total volume of mud discharged during the drilling of a well
is quite variable, but usually falls in the range of 100 to 400 metric tons.
When discharged, the drilling mud forms a plume which drifts away from
the rig with the prevailing current. Fractionation of the drilling mud occurs
rapidly as dense particulates settle to the bottom and fine clay-size particu-
lates and soluble materials are carried downcurrent. Substantial dilution may
take place in the discharge pipe before the mud is discharged. Drilling mud
concentration, measured as total suspended solids, percent transmittance, or
concentration of particulate or soluble mud-associated metals, decreases
rapidly with distance from the rig. Background values for total suspended
solids and soluble/particulate metals concentrations are usually reached
within 100-1,000 meters downcurrent of the discharge. Using ultratrace
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techniques for participate barium, it is possible to trace a drilling mud
plume for several km. Percent transmittance values, indicative of fine
suspended clay-size particulates, usually reach background somewhat further
downcurrent than suspended solids concentrations. The time required for the
drilling mud plume to be diluted and dispersed to background levels is 30 to
100 minutes.
Rate'of dilution to background of discharged drilling mud is affected by
the rate of drilling mud discharge, current speed and turbulence, water depth
and other hydrographic parameters. Dilution rate can be controlled somewhat
by controlling rate of mud discharge and discharge pipe design and position in
the water column.
Virtually all of the drilling mud solids and some of the soluble components
eventually are deposited on the bottom under the discharge pipe and downcurrent
from it. Maximum drilling mud accumulation on the bottom usually occurs a
short distance downcurrent from the discharge. The most useful tracer of dis-
tribution of drilling mud in bottom sediments is barium. Surficial sediments
(upper 1 cm) up to about 2 km downcurrent from the mud discharge may contain
elevated concentrations of barium. Elevated concentrations of chromium, lead,
and zinc may occur in bottom sediments near the discharge. Concentrations of
these metals in sediments fall to background concentration at a much shorter
distance from the discharge than does sediment barium concentration.
The major environmental concerns about discharge of used drilling muds to
the ocean are that they may be acutely toxic or cause deleterious sublethal
effects in sensitive organisms and ecosystems and that heavy metals associated
with drilling muds may be accumulated by marine organisms to dangerous concen-
trations.
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A majority of major drilling mud ingredients are biologically inert
or have a very low order of acute or chronic toxicity. Of the major drilling
mud ingredients, only chrome- and ferrochrome-lignosulfonates can be considered
at all toxic. Their toxicity is quite low to all but a few sensitive species
(e.g., some corals). Minor ingredients of some environmental concern include
sodium phosphate salts, detergents, biocides (only paraformaldehyde is permitted
for offshore disposal), chromate salts and asphalt/oil-based ingredients. Ordin-
arily, these materials are not used in large enough quantities to cause concern.
Their concentrations should be kept low in drilling muds destined for ocean
disposal. Where possible, less toxic substitutes should be used.
To date, the acute toxicity and sublethal biological effects of more than
20 used offshore-type drilling muds have been evaluated with more than 60
species of marine animals from the Atlantic, Pacific, Gulf of Mexico and Beau-
fort Sea. Representatives of five major animal phyla have been tested, including
Chordata, Arthropoda, Mollusca, Annelida and Echinodermata. Larvae and other
early life stages, and oceanic species (considered to be more sensitive than
adults and estuarine species to pollutant stress) were included. In all but
a few cases, acute toxicity, usually measured as 96-hr. LC50, was 10,000 ppm
or higher drilling mud added. The lowest acute LC50 value was 500 ppm for stage
I larvae of dock shrimp Pandalus danae exposed to a high density ferrochrome
lignosulfaonte drilling mud from Cook Inlet, Alaska. Chronic or sublethal
responses were observed in a few cases at concentrations as low as 50 ppm.
Field studies of drilling mud plume dilution and dispersion reveal .that
drilling mud concentrations high enough to cause acute or sublethal damage to
the most sensitive species and life stages will occur only in the immediate
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vicinity of the drilling mud discharge .(to less than 1,000 m downcurrent)
and only for a very brief time during bulk discharges (generally less than 2
hours)(T We can conclude that there is little or no danger of measureable- -
adverse effect on water column organisms from discharge of used water-ba^se'd"
drilling muds to the ocean.
Benthic fauna may be vulnerable to damage from settling drilling mud and
cuttings solids, through burial or chemical toxicity. Accumulation of drill-
ing muds in coarse bottom sediments may change sediment texture and thereby
affect recruitment to the benthos of planktonic larvae. At environmentally
realistic levels of drilling mud in sediment, species composition of the benthic
community changes toward a more si It/clay-tolerant assemblage. The species
most sensitive to drilling mud in the water or sediments appear to be very
sensitive to high suspended particulates concentrations. Limited field studies
indicate that recovery of the benthic community from any effects of discharged
drilling mud is likely to be very rapid (within a few..months).
Heavy metals associated with drilling muds have a very limited bioavail-
ability to marine animals. Chromium is the most bioavailable of the mud-associated
metals. Accumulation from drilling mud of small amounts of barium, lead, cadmium
and copper has been demonstrated a few times, when marine animals were exposed to
high concentrations of drilling muds or drilling mud ingredients. Field
studies in the vicinity of drilling mud discharges have not provided any
convincing evidence of metal accumulation by resident marine fauna. More research
is needed on the long-term bioavailability to benthic marine organisms of metals
from sediments contaminated with realistic amounts of used drilling muds.
Discharge of used water-based drilling fluids to the ocean or exposed
coastal waters, where rapid dispersion and dilution is possible, poses no as yet
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5 .
measureable hazard of more than very localized and transitory impact on the
marine environment. Even in the small temporal and spatial domain in which
an adverse impact can be observed or predicted, damage is likely to be of a low
order of magnitude and restricted primarily to the benthos. Metals associated
with used drilling fluids have a very limited bioavailability to marine organ-
isms, so there is no danger of food web transfer or biomagnification of mud-
associated metals to commercial fishery species or Man. These conclusions apply
to standard or typical water-based drilling fluids currently in use for explora-
tory drilling in U.S. coastal waters and outer continental shelf. Highly
modified or specialized mud formulations or completely new formulations or ;
ingredients that might be introduced may behave quite differently in the marine
environment than the majority of drilling muds evaluated to date.
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INTRODUCTION
Well over. 23,000 oil wells have been drilled to date in the
coastal and outer continental shelf waters of the United States (McAuliffe
and Palmer, 1976; Managhan et al., 1977). Offshore exploration for oil
is expected to increase substantially in the coming decade as onshore re-
serves are depleted. There is a growing concern in this country and
abnoa-d that materials discharged from offshore oil platforms during
normal drilling and production activities might have adverse short-term
or long-term impacts on the marine environment.
One such material is drilling fluid (sometimes called drilling
mud). Large volumes of drilling fluids are used in offshore drilling
operations. Between 100 and 400 metric tons of drilling fluid may be
used to drill a single well (Shinn, 1974;- Hrudey, 1979). Water-based
muds, but not oil-based muds, may be permitted for discharge to the
ocean. Used drilling muds are often discharged intermittantly in small
amounts during drilling and in bulk quantities at the end of the drilling
operation (Shinn, 1974; McGuire, 1975; Ray, 1979). Approximately 110,000
tons of used drilling muds are discharged to the ocean each year (NAS,
1981).
The two major environmental concerns relating to discharge of
used drilling fluids to the oceans are that: 1) the drilling fluids may
be acutely toxic or produce deleterious sublethal responses in sensitive
marine species or ecosystems, and 2) metals present in some drilling
fluids may be accumulated by marine organisms to concentrations that
could be harmful, to the organisms themselves or to consumers, including
Man, of fishery products.
There is a rapidly-growing body of scientific research, both
published and unpublished, which addresses these concerns. The purpose
of this review is to summarize and critically evaluate this scientific
literature with the objective of drawing some general conclusions about
the biological fate and effects of discharged used drilling muds in the
marine environment.
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DRILLING FLUID COMPOSITION AND USAGE
History
Drilling fluids were introduced for rotary drilling in 1913 to
counteract blowouts due to insufficient hydrostatic head to balance
pressures in the formations being drilled. The first drilling fluids
were simply aqueous slurries of formation muds. By 1921 drilling fluid
properties were being controlled through the use of additives. With
this, came development of techniques for testing drilling mud properties
and the development of ever increasingly complex mud formulations. Drill-
ing fluid engineering was an established field by the time the first
offshore well out of sight of land was drilled in 1947. Today there are
over one-thousand trade-name products available for drilling fluid
formulation (World Oil, 1977), representing about 55 different generic
compounds or formulations (McMordie, 1975). Ranney (1979), in his re-
view of crude oil drilling fluids, describes over 250 drilling fluid
chemicals or processes patented in the United States since 1974. Of all
the chemicals available for custom-formulating drilling muds, only about
10 to 15 are actually used for mud formulation for a typical well. Four
chemicals (barite, bentonite clay, lignite, and lignosulfonate) make up
more than 90 percent by volume of most water-based drilling muds (Perricone,
1980). Most of the chemicals and processes available are used only when
certain difficult technical problems are encountered during the drilling
operation. An example of chemical modification of a drilling mud to
solve specific down-hole problems will be presented below. During drilling,
the mud engineer continually tests the drilling mud and adjusts the com-
position of the mud to counteract changes in down-hole conditions. Thus,
no two muds are identical, even when taken from different depths in the
same hole.
Functions
Modern drilling fluids serve several functions integral to the
whole drilling operation. Drilling fluids must:
1. transport cuttings to the surface and hold them in
suspension if circulation is interupted;
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2. cool and lubricate the drill bit and drill pipe;
3. balance subsurface and formation pressures preventing
a blowout;
4. coat the well bore wall with an impermeable fitter cake
to prevent loss of drilling fluid to permeable forma-
tions and to protect clay and shale formations from
water imbibition;
5., support part of the weight of the drill string and
collars;
6. minimize corrosion to the drill string and casings.
Drilling fluids are formulated to perform these functions
optimally (Monaghan et al., 1977; McGlothlin and Krause, 1980). Mud
composition is changed as the relative importance of the different
functions changes with well depth and formation characteristics.
Transport of cuttings can sometimes be accomplished with water
alone. However, in most situations, a medium of higher viscosity is re-
quired. Ideally, the transport medium should be thixotropic. That is,
it should have a relatively low viscosity while flowing, but should be-
come highly viscous or even gel when stationary. Low viscosity is
desired for ease of pumping. High viscosity and gel strength (ability
to hold solids in suspension) are required to lift drill cuttings' up
the annulus of the hole and to prevent cuttings and weighting material
from falling down the annulus when mud circulation is stopped.
The material most widely used to produce this thixotropic
fluid is bentonite clay. Attapulgite and sepiolite clays are sometimes
used in muds containing high salt concentrations.
With use, drilling muds may become excessively viscous due to
accumulation of fine drill cuttings solids (especially clays from shale
formations). Thinners are added to the mud to lower viscosity and in-
crease the carrying capacity of the mud for drill cuttings. Chrome or
ferrochrome lignosulfonate and lignite are the thinners most frequently
used in drilling operations in U.S. coastal waters.
Density (specific gravity) of drilling mud is controlled by
adding insoluble, inert powders of high specific gravity. Iron oxide,
-------
iron phosphate, and galena have been used in the past as weighting agents.
Today barite (barium sulfate) is used almost exclusively as weighting
agent for water-based drilling muds. Weighting of muds is required to
counter high pressures that may be encountered in formations penetrated
by the drill bit. If hydrostatic pressure provided by the weight of
drilling mud is less than the pressure encountered in a drilled formation,
fluid or gas will be forced into the drill hole from the formation, con-
taminating the mud system or, if pressure differential is great enough,
causing a blowout. Since formation pressures tend to increase with
depth, amount of barite in drilling mud is usually increased with depth
drilled.
A variety of chemicals and mixtures are used to control filtra-
tion (loss of drilling fluids from the borehole to the formation) and to
inhibit hydration and swelling of porous shale and clay formations;
Starches, cellulose polymers, or acrylic compounds are most frequently
used with bentonite clay for these purposes. Excessive loss of drilling
fluid to very porous formations is combatted by addition of "lost
circulation" materials which include solids of various sizes and shapes
(e.g., walnut shells, mica, ground paper, leather or formica, etc.).
Some drilling muds are slightly corrosive. Corrosion of metal
parts of the drill string is prevented by adding small amounts of de-
foamer such as aluminum stearate. Oxygen, carbon dioxide, and hydrogen
sulfide from the formation or elsewhere can cause serious corrosion
problems. Oxygen may be removed by addition of small amounts of
sodium- or ammonium-bisulfite. Carbon dioxide, is neutralized with
sodium hydroxide or lime. Hydrogen sulfide problems are usually handled
by addition of any of several metal salts (sodium dtcliromate, zinc car-
bonate, zinc sulfonate, zinc chromate, etc.).
Under ordinary conditions, the standard drilling mud formulation
provides adequate 'cooling and lubrication of the drill string. However,
if the borehole becomes crooked or an intentionally curved directional
well is being drilled, additional lubrication may be needed. A wide
variety of lubricants are available. Biodegradable vegetable oils
-------
,10
(modified or unmodified) are used frequently where the drilling mud is
destined for ocean disposal. Diesel oil may be required to free stuck
pipe.
Bactericides are occasionally required to inhibit fermentation
of organic polymers (especially starch) or to prevent reduction of sul-
fates in the mud to hydrogen sulfide by sulfate-reducing bacteria. Most
muds are sufficiently alkaline to inhibit microbial activity. Currently,
all bactericides used in drilling muds are regulated by the EPA under the
Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and by specific
regulations of the U.S. Geological Survey. Paraformaldahyde is one of the
few products approved to date. Pentachlorophenol and other chlorinated
phenols, formerly used in small amounts in some drilling muds, are pro-
hibited for offshore use by U.S.G.S. and frequently by specific stipulation
in NPDES permits. Chlorinated phenols may be used in packing fluids. These
are not discharged to the ocean, but remain in the borehole at the end of
drilling.
Drilling Mud-Handling System
The drilli'ng mud system is an integral part of any modern drill-
ing rig (Figure 1). The mud system consists of several components (Ray,
1979). Several mud tanks are situated on the rig adjacent to the drill
floor. Mud holding capacity of these tanks on an offshore rig may range
from 1,000 to 2,500 barrels (42,000 - 105,000 gallons). Mud is pumped
from the mud tanks to a slugging tank where materials may be added to the
mud as needed. The mud is pumped from the slugging tank with a high volume,
high pressure pump (200 - 600 gallons per minute, 1200 - 3500 pounds per
square inch) through the mud hose to the kelley (drive section of the
drill pipe) on the drill floor. The mud passes under high pressure down
through the drill pipe and exits through nozzles in the drill bit where
it hydrolically removes cuttings.
The mud, carrying cuttings with it, then passes up through the
annulus (area between drill pipe and borehole wall or casing) to the mud
return line. Mud and cuttings then flow onto a series of shale shaker
screens of different mesh sizes. Cuttings are retained and fall into the
cuttings discharge hopper from which they are washed with a stream of water
down the discharge pipe to the ocean. The mud and fine drill solids fall
-------
11
MIXING HOPPER
SLUGGING TANK
KELLY
.S MUDHOSE
MUD RETURN LINE
DEGAS5ER
MUD TANKS
(SUCTION
TANKS)
SHALE
SHAKER
CUTTINGS
DISCHARGE
HOPPER
MUD FLOW
AT DRILL
BIT
DISCHARGE
TO SURFACE
SAND TRAP
SEA SURFACE
i>-DRILL_ COLLAR^ :;^^-\\;ฐ'/-;'-
:.*. BIT ';^:'':Vv;'.'.1 !"""'> '-v'.'-1'';."
'.V:-:'.':>'-':'-'-:.';'".:";v''-:->.';-:v'ฐ;.:V.:: ;':..7\;^:'..>;
:.ซ>:>.:;- .?...;:'..:>-.'..: :>; v.\
' ^'. i '' ':'".:''- ' :>:.ฐ;''' '>';; : vV '.\v--ff''-
'''''' '"
Figure 1. The drilling mud-handling system of a typical offshore
exploratory drilling rig (From Ray, 1979).
-------
12
through the shaker screens and are recirculated to the mud tanks for
circulation back down the hole. On the way, they pass through a degasser,
desander, desilter, mud cleaner and centrifuge which remove gases and
specific size ranges of drill solids from the mud. These are discharged
with washwater to the ocean.
Drilling Mud Composition
Major drilling mud ingredients and the amounts used are listed
in Table 1. It is apparent that many of the major drilling ingredients
are sold under a variety of trade names. As with other materials sold
under several trademarks by different manufacturers, actual composition of
a particular generic material (e.g. chrome lignosulfonate) may vary slightly
according to brand name. Several of the ingredients listed in Table 1 are
used only occasionally in drilling muds. The concentration ranges given
are the amounts typically used when that material is called for in a mud
formulation.
Composition of several typical drilling fluids is summaried in
Appendix I, Tables la. -8&. These muds were used in the Joint Bioassay
Monitoring Program sponsored by the Offshore Operators Committee in com-
pliance with NPDES permit requirements for lease areas 40 and 49 on the
Middle Atlantic outer continental shelf. These drilling muds are con-
sidered typical of those used for exploratory drilling on the U.S. outer
continental shelf. Several of these mud types may be used in sequence to
drill a single well.
Drilling Mud Programs
Tables 2 and 3 give examples of how mud composition is changed
with depth during drilling of a typical coastal or offshore well. KC1-
type muds are used frequently onshore and offshore in the Canadian Arctic
for shallow drilling or where shale is encountered (Hrudey, 1979). Potassium
chloride (potash) in the mud acts as a flocculent and reduces shale swelling
by adsorbing to the clay matrix and stabilizing the shale structure. Shale
swelling from water imbibation can cause the drill stem to become stuck in
the hole. KC1 muds also are particularly useful for drilling through perma-
frost. After drilling has progressed through the permafrost zone, concentration
-------
13 .
Table 1. Major chemical ingredients (annual consumption, 10,000 tons or more) of
drilling muds, their major trade names, and quantities and concentrations
used (From API, 1978).
Consumption Concentration Range
Material/Trade Names (Tons/Year) in Mud (Ib/barrel)
BARITE 1,900,000 25-700
Arcobar Howcobar Mil-Bar
Baroid .Imcobar Ob Hevywate
Bascowate Lamco Bar Pre-Mix .Wate
Del-Bar Magcobar Trip-Wate
BENTONITE CLAYS 650,000 5-35
Western Bentonite
Arcogel Halliburton Gel : Mil gel
Aquagel Hydrogel Ob Bengel
Bascogel Imco Gel Premium Gel
Chemcogel Lamco Gel Pre-Mix Gel
Delgel Magcogel United Gel
Southern Bentonite (Processed Calcium Bentonite)
Arco Clay High Yield Clay Lamco Clay
Baroco Imco Klay Ob Clay
Processed Western Bentonite
Basco Double-Yield Imcohyb. Super-Col Quik-Gel
Extra Hi.Yield Gel Kwik-Thik Super Gel
ATTAPULGITE/SEPIOLITE CLAYS 85,000 10-30
Attagel Ob Chlorogel
Attapulgus Drilling Clay 100 Salgite
Attapulgus Drilling Clay 150 Salt Gel
Basco Salt Mud Salt Mud
Chemco Salt Gel Salt Water Gel
Del-S-Gel Sea Mud
Geogel Thermogel
Imco Brinegel Zeogel
Lamsalgel
LIGNOSULFONATES 65,000 1-20
Calcium
Kembreak Lignox
-------
TABLE 1. Continued
14
Material/Trade Names
Consumption
(Tons/Year)
Concentration Range
in Mud (Ib/barrel)
Chromium and/or Iron
Archochrome
Archochrome Modified
Basco 300
Basco Drilflo
Chemco 727
CLS
Other Metals and Mixtures
Ferrocal
Lamco Perma Thinz
Imco VC-10
Ob CLS
Primix CLS
Q-Broxin
Rayvan
Spersene
Stabl-Vis
Uni-Cal
Arco Blend
CL-CLS
Imco RD 111'
Ngage
XKB-T.hin
SODIUM HYDROXIDE (NaOH)
SODIUM CHLORIDE (NaCl)
LIGNITE
50,000
50,000
50,000
Natural
Arcolig
Bascolig
Carbonox
I Kolite
Del Lignite
Causticized
Arcotone
Basco Cau-Lig
Causticized Lignite
CC-16
DMA Lignite.u
Chromium
DMA Lignite
Imco Lig
Lamco Lig
Ligco
Ob Lignite
Pre-Mix Lenox
Superlig
Tannathin
Imco Thin
Imco IE Par
K-Lig
Ligcon
Lignothin
Shale Lig
Super Treat
Uni-Thin
XKB Lig
Chrome Lig
Cl-Cls
Del Lignite
Stabil-Prop
XP-20
Zinc
Milcon
DIESEL OIL
SODIUM CARBONATE (Na2C03)
30,000
20,000
1-5
10-125
1-25
3-275
0.1-4
-------
15
TABLE 1. Continued
Material/Trade Names
Consumption
(Tons/Year)
Concentration Range
in Mud (Ib/barrel)
LOST CIRCULATION MATERIALS
Cellophane
Cotton Seed & Rice Hulls
Ground Fromica
20,000
Ground Leather
Bround Paper
Ground Pecan & Walnut Shells
STARCH
Pregelatinized
Imcoloid My-Lo-Jel
Impermex
Chemically Modified and/or Fermentation-Resistant
Arcoloid
Filtrol
Arco Permaloid
Basco
Dextrid
Imco Permaloid
Magco Poly-Sal
Starlose
CELLULOSIC POLYMERS
Sodium Carboxymethyl Cellulose (CMC)
12,500
Carbose
Cell ex
Driscose
Drispac
Hydroxyethyl Cellulose (HEC)
Safe-Vis Safe-Vis X
CALCIUM CHLORIDE. (CaCl?)
CALCIUM HYDROXIDE/CALCIUM OXIDE (LIME)
(Ca(OH)2, CaO)
ASPHALT/GILSONITE
Natural, Treated, and Oxidized
12,500
10,000
10,000
Black Magic
Filter Rate
Form a Seal
HME
Sulfonated
Hole Coat
Hydroproof
Pre-Mix Wallkote
Protectomagic
Stabil Hole
Superdril
Super Lube Flow
X-Pel G
No Sluff Soltex
ASBESTOS
Flosal . Shur Lift
Super Visbestos Visbestos
10,000
5-50
Mica
Wood & Cane Fibers
0.25-5
10-200
2-20
1-50
1-10
-------
16
Table 2. Composition of drilling muds used at four depth intervals to drill exploratory
wells offshore in the Canadian Arctic (Data from Bryant, 1976 and Hrudey, 1979),
Mud Description
Mud Additive
Normal Use Range,
mg/1.(Bryant. 1976)
Concentration
Found by
Hrudey, 1979
(mg/1)
Surface Hole Mud
Intermediate Hole Mud
Bottom Hole Weighted Mud
Bottom Hole Weighted Mud
(Drill Stem Test)
Bentonite
Polymer
Caustic
Potash
Bentonite
Polymer
Caustic
Barite
Lignosulfonate
Bentonite
Caustic
Barite
Lignosulfonate
Na Acid Pyrophosphate
Bentonite
Caustic
Barite
Lignosulfonate
Na Acid Pyrophosphate
15,000 - 107,000
1,500 - 4,300
730 - 5,800
29,000 - 58,000
15,000 - 170,000
1,500 - 4,300
730 - 5,800
90,000 - 2,000,000
2,900 - 29,000
15,000 - 107,000
730 - 5,800
90,000 - 2,000,000
2,900 - 29,000
280 - 1,500
15,000 - 107,000
730 - 5,800
90,000 - 2,000,000
2,900 - 29,000
280 - 1,500
36,000
1,500
750
30,000
48,000
1,500
750
30,000
750
69,000
2,500
650,000
10,000
250
75,000
4,500
1,500,000
30,000
750
-------
Table 3. Amounts of drilling mud ingredients added to drilling mud in different depth intervals during
drilling of an exploratory well in the Gulf of Mexico (Adapted from Monaghan et al., 1977).
Mud Ingredient
Barite
Bentonite
Ferrochrome Lignosulfonate
Lignite
Caustic Soda (NaOH)
Sodium Bicarbonate
SAPP (Sodium Acid Pyrophosphate)
Aluminum Stearate
Amount
0-2,830 ft. 2
0
59,900
1,500
1,500
8,700
0
300
0
of Material Added i
,830-6,150 ft. 6,
110,800
13,000
6,600
4,500
4,400
600 .
0
0
n Depth Interval
150-7,450 ft.
336,500
3,000
11,300
8,000
10,000
0
0
0
dbs)
7,450-9,800 ft.
1,075,760
7,700
8,600
7,600
55,400
0
300
300
Total Used
(Ibs)
1,523,060
83,600
28,000
21,600
78,500
600
600
300
Total Ingredients Added 71,900 139,900 368,800 1,155,660 . 1,418,000
-------
18
in the mud of KC1 is decreased by dilution and wash-out, and concentration
of barite and lignosulfonate is increased (Table 2). More barite and
lignosulfonate are added as the depth of the hole is increased.
Mud composition changes during use due to addition of cuttings
produced at the drill bit and due to mud washing activities on the platform
to remove drill cuttings. New ingredients are added periodically to make
up for that lost or diluted during mud use or to change properties of the
mud. This is seen in Table 3 where amounts are listed of materials added
to the mud at different depth intervals. The near-surface mud is
mainly bentonite and caustic soda with small amounts of lignosulfonate
and lignite. Barite and ferrochrome lignosulfonate are added in increas-
ing amounts in subsequent depth intervals.
Drilling fluids practices and procedures follow a definite sequence
during a typical exploritory drilling operation in coastal or outer con-
tinental shelf waters. The actual depths at which mud programs are changed
will depend on types of formations encountered at different depths.
The first 150 feet or so of the hole is jetted with seawater and
the resulting seawater mud is returned directly to the sea floor without
being pumped to the rig. Typically, while drilling to 1,000 feet, only
seawater is used as a drilling fluid and it is discharged overboard. If
formation clays do not make a sufficiently viscous mud, bentonite clay is
added to the system. This mud, containing water, formation clays, bentonrite,
and occasionally a small amount of barite and lime, is called a spud mud
(Appendix I, Table 4a'-).- Approximately 1,000 barrels of spud mud containing
about 6 tons of bentonite clay may be used in a typical well. A conduction
pipe (casing) is then run to 1,000 feet and cemented in place. The spud
mud is discharged to the ocean.
While drilling the remainder of the hole, the drilling fluid is
continuously recycled through the mud system as described above. Some drill
mud is discharged with the drill cuttings. In addition, some drilling mud
is discharged overboard periodically as excess amounts are generated from
retention of fine drill cuttings, addition of mud ingredients to change its
properties, and addition of water during washing.
-------
the"
5lT "
19
Between 1,000 and 6,000 feet, the mud used may be a seawater gel
mud (Appendix I, Table 6a) or a lightly treated seawater lignosulfonate mud
(Appendix I, Table7a). At about>6,000 feet the system may be converted to a
freshwater lignosulfonate mud (Appendix I, Table8a). The decision is based
on the relative economics of transporting freshwater from shore versus the
higher maintenance costs of the seawater mud system. As depth of the wel'
increases, larger portions of barite and lignosulfonate are added. The mud
may have to be treated with a variety of other additives for lubrication,
filtration control, lost circulation, etc. After the well is drilled to depth,
drilling mud remaining on board is usually discharged to the ocean. Typical
offshore mud programs are summarized in Tables 2 and 3.
Sometimes difficulties are encountered during drilling that require
a much more complex mud program. This is seen in Tables 4 and 5 which summarize
the mud program for an exploratory well drilled in Mobile Bay, Alabama. This
well was drilled to a greater depth (21,113 feet) than all but 0.1% of the
wells drilled in 1978-1979 in the United States. Several down-hole problems were
encountered while the well was being drilled (Jones, 1980). These included
excessively high temperatures which caused high-temperature gelation and thermal
degradation of the lignosulfonate mud system, massive anhydride (calcium sulfate)
formations which resulted in serious salt contamination of the drilling fluids,
and presence of hydrogen sulfide gas. The high temperatures (up to 414ฐF) were
the most serious problem. Lignosulfonates undergo serious thermal degradation
at temperatures in excess of about 330ฐF (165ฐC) causing thickening and gelation
of the drilling mud (Carney and Harris, 1975; Skelly and Kjellstrand, 1966).
Chromium VI in the form of sodium chromate is added to stabilize the lignosulfon-
ate (McAtee and Smith, 1969; Skelly. and Dieball, 1969).
The mud program for this well can be divided into three portions
reflecting three depth intervals (and drilling conditions) in the hole. A
low solids, non-dispersed mud was used in the first portion. It consisted
primarily of clays and caustic soda in water with increasing amounts of barite
added with depth for weighting. Small amounts of several additives were
added to combat stuck pipe, foaming, lost circulation, etc. This pro-
gram was continued down to about 9,600 feet. The mud system was converted
-------
Table 4. Tire/depth MUory of drilling mud Ingredients usage during drilling of Mobil Oil Company's 11-76 well til
Habile Bay. Alabama, Units are one thousand pounds (Adapted frw Jonei, 1980).
Date Interval
Depth Interval (feet)
Hud Component
1. Barlte
2. Sentonlte Clay
3. Caustic Soda (KaOH)
4. vlscoslflers
5. Attapulgite Clay
6. Na Polyacrylawlde Polymer
7. Na Acid Pyrophosphate (SAPP)
8. Soda Ash (llagCOj)
9. lost Circulation KaUrla]
10. Detergent
11. lignite
12. Polyanlonlc Cellulose Polyner
13. Spotting Fluid
u. Eiulslfleri
IS. Surfactant
16. Ground Pecan Shells
17. lubricant
1C. Ground Hlca
19. Defoanant
20. NaPolyacrylate Blend
21. Aluminum Stearate
22. Ferrochronw llgnosulfonate
23. 5odlun Chromate
24. Ferrochrome Llgnosulfonate/tla Bichromate
?S. High Temp. Ferrochrone llgnosulfonate
27. line (C.(OM);)
29. H2S Scavengar
30. Sulfonated Asphaltene
650-3,110
63.0
BO. 6
30.6
9.9
55.5
0.02
3.1
7.0
2.08
1.30
6.0
0.5
10.0
.
'-
-
.
.
.
-
-
-
'
-
2,514-5.950 5,950-5.962
73.8 99.4
21.2 24.2
16.1 20.0
0.75
9.0
-
1.2 2.0
13.4
-
.
12.0 4.3
'1.7
-
0.17
0.16 0.41
2.25
7.54
4.75
.
- .
-
-
/ -
.
.-
5.963-9,978 10.101-13,761
114.8 42.4
52.5 57.2
20.0 43.1
-
-
0.03
0.9
5.3
-
11.0 10.5
0.5 0.2
-
. -
0.45 0.45
0.30 . 1.38
-
.
0.24 ' 0.31
0.15 0.06
0.15 0.45
11.85
-
-
., -
.
-
13,940-14,553
136.0
60.7
22.4
-
- .
0.2
12.98
-
- '
12.0
0.85
-
0.82
-
.
-
-
12.65
0.90
-
.
-
14,567-14,568 14,598-15,824 16,000-17,917
' 116.0 62.1 264.0
61.7 53.4 43.8
2.8 13.9 29.1
.
5.1 2.9
5.2 1.8
-
5.6
'0.55 2.5
. .
-
0.12
2.20 0.98
6.59
1 .80
-
0.05
-
11.10 g.95
1.00 2.90 3.90
4.50 8.25 25.25
2.95 9.20
- - 2.40
.
.
18,023-19,374
352.1
47.6
37.2
-
-
-
-
-
-
5.6
-
'
-
3.42
1.10
0.75
.
-
-
5.20
24.30
9.25
6.25
-
-
19,374-20,618
530.2
45.7
20.0
-
-
-
-
3.9
-'
-
1.5
-
2.15
1.24
-
-
0.15
5.90
4.80
21.50
12.30
5.70
3.00
-
20.680-21,113 21.100-20,550 20,550-12.500 12.500-12,300
188.0 146.2 122.1 80.0
124.1 8.8 11.4
25.2 10. 0> 15.8 6.7 .
.
31.6 12.9
. .
1.2 . 0.1
.
12.5 1.5 - 1.0
3.05
8.15 - -
' -
0.04
1.30 - -
0.37 - - -
3.35
.
.
0.82
i 24.15 3.05 3.60
8.00
5.65 2. IS - 4.10
19.50 1.00 1.40
20.55 1.80 2.00
5.15 , 2.10
5.10 - - .
21.113
Total
2.130.1
692.7
312.9
10.65
109.0
O.CS
15.4
50.7
2.08
1.3
76.4
16.95
18.15
0.17
3.78
12.65
16.8J
10.65
0.55
0.26
1.57
82.25
27.5
95.7
55.6
6.C5
38.7
9. ฃ3
10.25
S. 10
-------
21
Table 5. Description of drilling mud ingredients used in Mobil Oil
Company's #1-76 well in Mobile Bay, Alabama. Numbers
refer to numbers in the mud component column of Table 4
(From Jones, 1980).
1. Imco Bar. Barite (63804); weighting agent.
2. Imco Gel. Western bentonite clay (sodium montonorillonite) ; viscosifier.
3. Caustic soda (NaOH); pH control agent.
4. . Fl.osal & Imco Shurlift. Acid-soluble chrysotile asbestos fibers;
viscosifier.
5. Imco BrinegeL Attapulgite clay; viscosifier for salt-water muds.
6. Imco Floe. Polymeric sodium polyacrylamide; flocculant.
7. SAPP. Sodium acid pyrophosphate; calcium precipitant.
8. Soda ash. Sdoium carbonate (Na); counteract calcium sulfate
9. IMCO KWIK-SEAL. A blend of nut shells, cellophane flakes, paper, and
mica; lost circulation material.
10. IMCO MD. Modified alkanolamid and sodium acid pyrophosphate buffered in
an aqueous base; detergent.
11. IMCO LIG. North American lignite coal. Thinning agent.
12. DRISPAC. High moleculer weight polyanionic cellulosic polymer; fluid loss
control er and viscosifier.
13. IMCO SPOT. Weighted mixture of calcium oleate and asphalt; spotting fluid,
used to free stuck drill pipe.
14. IMCO SWS. Blend of sulfonated fatty acid derivatives; emulsifier.
15. IMCO DEFORM-L. Phosphoric acid tributyl ester; surfactant.
16. IMCO PLUG. Ground pecan shells; lost circulation material.
17. IMCO LUBE 106. Blend of glycerol mono-oleates and mixed long chain
alcohols; lubricant.
18. IMCO MYCA. Ground mica; lost circulation material.
19. IMCO FOAMBAN. Blend of phosphoric acid tributyl ester, alcohol, and
refined hydrocarbon carrier; defoamant.
20. IMCO GELEX. Sodium polyacrylates; bentonite extender.
21. Aluminum stearate. Insoluble aluminum salt of octadecanoic acid;
defoamant.
22. IMCO VC-10. Ferrochrome li.gnosulfonate; dispersing and thinning agent.
23. Sodium chromate. NagCrO/rlOHoO; prevents high temperature gellation of
water-based drilling mua.
24. IMCO RD-III. Blended ferrchrome lignosulfonate containing added sodium
bichromate; heat-stable dispersant and thinning agent.
25. IMCO POLY-Rx. Blend of lignosulfonates, polymers, and sodium carbonate;
heat-stable dispersant thinning agent.
26. IMCO SP-101. Sodium polyacrylate polymer; fluid loss agent.
27. Lime. Ca(OH)2; source of calcium for spud and lime muds.
28. IMCO HOLECOAT. Blend of water-disperable asphalts; lubricant and fluid
loss agent.
29. IMCO SULF-X II. Mixture of zinc sulfonate, sodium nitrilotriacetic acid,
and zinc carbonate; hydrogen sulfide scavenger.
30. Saltex. Sulfonated asphaltene;' lubricant and hole stabilizer.
-------
22
to a dispersed system between 9,000 and 10,000 feet by addition of lignite
and then ferrochrome lignosulfonate. This program was continued down to
about 14,500 feet. Large anhydride formations were encountered in this
segment. SAPP, soda ash and other chemicals were added to counteract this
problem. By 14,500 the mud was a heavily treated lignosulfonate mud as
more and more chemicals were added to counteract problems. As temperatures
increased, temperature extenders (Gelex, chromates, polymers) were added
in increasing amounts. Hydrogen sulfide was encountered near 19,000 feet,
requiring addition of an HLS scavenger.
In all, thirty products were used to formulate the muds used in
this drilling mud program. This is two to three times the number of
materials used in most mud programs. It should be pointed out that the State
of Alabama had prohibited all discharges from this exploritory rig to Mobile
Bay. The drilling muds were never intended for ocean disposal. They were
disposed of on land. However, drilling mud from this well has been used
extensively in the marine toxicology research discussed elsewhere in this
review.
Trace Metals in Drilling Muds
The ingredients in drilling muds of major environmental concern
are the trace metals. Many elements such as calcium, magnesium, aluminum,
sodium, potassium, chlorine, etc. are normal major components of clays and
soils, have a relatively low toxicity, and therefore are of little environ-
mental concern in drilling muds, with few exceptions (e.g. potassium in KC1
muds poses a toxicological problem when the mud is discharged to fresh
water [Sprague and Logan, 1979]).
Accurate and precise analysis of metals in used drilling muds is
hampered by the fact that most drilling muds are extremely heterogeneous
and many of the metals are present in the form of extremely insoluble metal
salts (Hrudey, 1979; Kalil, 1980). Partly because of these problems, but
also because of variability in the purity of major ingredients like barite,
bentonite and lignosulfonate, published values for metals concentrations in
used drilling muds are quite variable (Table 6; Appendix I, Tables 2a-9a).
The metals of major concern are barium, chromium, cadmium, copper, iron,
mercury, lead and zinc. Arsenic, nickel, vanadium, and manganese also
-------
Table 6. Trace metal concentrations in drilling muds from different sources. Concentrations are in mg/kg dry weight
Drilling Mud
48 Samples Canadian
Arctic Muds
3 Barite CLS1 Muds
2 Mid-Atlantic CLS Muds
3 Mid-Atlantic 'CLS Muds
Baltimore Canyon CLS Mud
Gulf of Mexico CLS Mud
Gulf of Mexico Spud Mud2
Gulf of Mexico High Density CLS Mud2
Gulf of Mexico Mid-Onesity CLS Mud2
Mid Atlantic Low-Density CLS Mud
Gulf of Mexico Seawater CLS Mud
Gulf of Mexico Spud Mud2
Gulf of Mexico High Density CLS Mud
Gulf of Mexico Mid Density CLS Mud2
2 CMC3/Gel Muds Alaska4
XC Polymer Muds Alaska (20)4
XC Polymer/Unical Muds Alaska (6)4
CLS Muds Alaska (4)4
Gulf of Mexico CLS Mud
Mobile Bay Treated CLS Mud
1. CLS, chrome lignosulfonate; 2. The
4. Concentrations given on a wet-weigt
Ba
NA
NA
Cr
0.1-909
NA
229,100-303,700 1,112-1,159
823-19,300
202,000
133,00
NA
NA ,
NA
NA
NA
NA
NA
NA
4,400-6,240
720-1,120
NA
800-7,640
90,000
NA
same muds were
it basis; 5. NA,
57-90
850
200
51
257
396
596
485.2
10.9
229.9
416.7
28-63
66-176
56-125
121-172 '
500
5,960
analyzed by Page
not analyzed.
Cd
NA
0.16-54.4
0.6-0.8
<2
NA
NA
0.51
0.78
1.70
1.18
3.0
3.5
10.9 .
19.2
<0.5-0.6
<0.5-1.5
NA
<0.5
NA
NA
et al., 1980
Cu
Fe
<0. 05-250 0.002-9,250
6.4-307
5.8-7.7
NA
20 19
280 16
NA
NA
NA
NA
48.2
30.2
118.8
127.0
6.4-10.4
10-16
2.8-17.0
10-12
43 27
47 10
and McCulloch
NA
NA
NA
,000
,000
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
,000
,100
et al.,
Hg
NA
0.2-10.4
<0.05
-------
24
may be present at elevated concentration in some muds. Some of these metals
are added intentionally to drilling muds as metal salts or organometallic
compounds. Others are trace contaminants of major mud ingredients (Table 7).
Barium in drilling fluids is almost exclusively from barite (barium
sulfate) added to drilling mud as a weighting agent. Bentonite c.lay also
may contain some barium. Barium sulfate has a specific gravity of 4.3 - 4.5 g/cc
and a solubility in seawater of-approximately 224 yg BaSCh/ฃ (132 yg Ba/A)
(Desai et al., 1969). Chow'(1976) estimated the solubility of barium in surface
seawater to be 46 yg/kg based on a normal seawater sulfate concentration of 28 mM.
Recent analyses of surface waters of the Atlantic and Pacific oceans give values
generally in the range of 4-11 yg/kg dissolved barium (Chan et al., 1976; Chow,
1976; Chow and Snyder, 1980). Thus seawater is slightly under-saturated with
respect to barium.
Dissolved organic materials in seawater may increase the apparent
seawater solubility of barium somewhat, probably by binding the barium in a
soluble complex (Desai et al., 1969). Thus Liss et al. (1980) observed dissolved
barium concentrations in seawater suspensions of two synthetic drilling muds of
0.021 - 0.103 mg/ฃ. Three samples of used drilling mud analyzed by Liss et al.
(1980) contained 15-18 mg/i barium in the liquid phase. Presumably much of this
barium was complexed to soluble organics (e.g. lignosulfonate) in the mud.
The amount of barium sulfate added to a drilling mud may vary from
0 to about 700 Ib per barrel (0-2 kg/liter). Barium represents up to 30 per-
cent of the weight of dry ingredients in the mud (Ayers et al., 1980a). Because
of the extremely low solubility in seawater of barite, nearly all the barium
discharged to the ocean remains in particulate form as barite or barite-clay
.complex (Trefry et al., 1981).
Chromium in drilling muds is derived primarily from chrome- and
ferochrome lignosulfonates added to drilling muds as deflocculants and
thinners. Chromium concentration of several lignosulfonates is listed in
Table 7. In addition, Beckett et al'. (1976) reported the following values
for total chromium for three brands of lignosulfonate: Q-Broxin (ferrochrome
lignosulfonate), 19,500 ppm (mg/kg); Spersene (chrome lignosulfonate),
-------
Table 7. Trace metal composition of drilling fluid components. Concentrations are in mg/kg dry weight (ppm).
Material
Barite (vein deposits)
Barite (bedded deposits)
Barite
Barite
Barite
Barite
Barite
Barite
Barite
Bentonite Clay
Bentonite Clay
Bentonite Clay
Chrome Lignosulfonate
Chrome Lignosulfonate
Chrome Lignosulfonate
Chrome Lignosulfonate/Lignite 1/1
Ferrochrome Lignosulfonate (Peltex)
Iron Lignosulfonate (DFE 506)
Lignite
Ba
NA1 -
NA
NA
55,000
NA
NA
NA
501,000
NA
560
NA
NA
64
NA
NA
NA
NA
NA
NA
Cr
NA
NA
54
3.6
0-3
<10
2.5
NA
,11
3.3
<10
1.5
24,500
925
39,100
14,600
16,100
53
300
Cd
0.6-32
0.5-0.7
NA
NA
NA
<2
10.0
NA
NA
NA
<2
0.6
1.4
NA
<2
NA
NA
5.5
Cu
0.6-560
5.4-7.6
44
NA
4-30
NA
NA
91
290
NA
NA
NA
NA
8
NA
11
3.3
NA
Fe
200-59,000
2,500-6,000
34,900
NA
'30-1,500
NA
NA
21,700
9,500
NA
NA
NA
NA
1,250
NA
36,700
74,500
NA
Hg
0.3-28
0.13-0.26
NA
0.054
NA
<1
14.2
NA
NA
NA
<1
0.02
0.02
NA
<1
NA
NA
NA
Pb
< 2-3, 370
1-1.8
286
<1.0
0
<10
890
1,370
19
NA
<10
22.5
<1.0
2.5
10
<10
<0.25
<0.25
<1.0
Zn Others
<0;2-9,020 0.008-170 As
15-41 Ni
6-10 1.4-1. 8 AS
0.5-5.7 Ni
1,270
NA
NA
<5
2,100 25.7 As
2,750
19
NA
57
31.0 0.7 As
5.9 0.25 As
17 1,440 Mn
15
1.2
1.8
NA
Reference
Kramer et al . , 1980
Kramer et al . , 1980
Beak Cons., 1974
ECOMAR, 1978
Perricone, 1980
Ayers et al., 1980
Crippen et al., 1980
Trefry et al . , 1981
Trefry et al., 1981
ECOMAR, 1978
Ayers et al., 1980
Crippen et al . , 1980
ECOMAR
Crippen et al., 1980
Trefry et al., 1981
Ayers et al . , 1980
Beak Cons., 1974
Beak Cons., 1974
ECOMAR, 1978
PO
tn
NA = not analyzed
-------
26
5,000 ppm; Unical (chrome-modified lignosulfonate), 44,500 ppm. Of the
other major mud ingredients, barite and lignite also may contain some
chromium. In addition, inorganic chromium salts are sometimes added to
drilling muds for such purposes as high temperature stabilization of
lignosulfonate, corrosion control, and h^S scavenging. Typical used off-
shore drilling muds may contain 0.1 to about 1,200 mg/kg dry weight and
exceptionally to about 6,000 mg/kg total chromium (Table 6; Appendix I,
Table 2a - 8.a).
Lignosulfonates are byproducts of the sulfite pulping process in
paper manufacturing. The spent sulfite liquor is evaporated and desugared
(Perricone, 1980). The desugared liquor is then treated with sulfuric
acid and sodium dichromate. The sodium dichromate oxidizes the ligno-
sulfonate and cross-linking occurs. The hexavalent chromate is reduced
by the lignosulfonate to the trivalent (chromic) state and complexes with
the lignosulfonate. Chromium is probably coordinated with lignosulfonate
through phenolic oxygens, sulfonate groups, and carboxylic acid groups
(Knox, 1978) and is not readuly exchangeable (McAtee and Smith, 1969;
Skelly and Dieball, 1970).
Soluble chromates (Cr VI) are sometimes added to drilling muds
to improve their thermal stability and for corrosion protection. These
are chemically reduced quite rapidly to the more stable tfivalent state
(Cr III) (Skelly and Dieball, 1969; Moseley, 1980) in the presence of
chrome lignosulfonate, lignite, and other organic material in drilling
mud. In addition, hexavalent chromium may react with sodium hydroxide or
calcium hydroxide (lime), commonly added to mud,.to produce trivalent chromic
hydroxide which is insoluble (Moseley, 1980). Once chromium is reduced from
the +6 to the +3 valency state in seawater, it is not readily oxidized back
to the +6 valency state under normal conditions (Fukai and Vas, 1969;
Schroeder and Lee, 1975).
Chrome and ferrochrome lignosulfonates are quire soluble in water.
Knox (1978) reported that 500 g of ferrochrome lignosulfonate will dissolve
in one liter of water without precipitation, even at a pH of 10 typical of
drilling mud. When initially prepared, much of the chromium in ferrochrome
-------
27
lignosulfonate is associated with low molecular weight material (MW 1000-
4000) (Liss et al., 1980). With aging, particularly at alkaline pH
characteristic of drilling muds, much of the metal becomes associated with
high molecular weight material (about 100,000 MW) (Knox, 1978; Liss et al.,
1980). It appears that, in the presence of alkali, ferrochrome lignosul-
fonates is converted to lignosulfonate polymers highly cross-linked by
the metals or to polymerized chromium and hydrous.oxides incorporating
lignosulfonate complexes (Liss et al., 1980).
In a drilling mud during normal usage, chrome- or ferrochome-
lignosulfonate becomes adsorbed to the clay particles. It is thought that
the metals adsorb to the clay by displacing the sodium in the clay matrix.
The lignosulfonate is attached to the clay by being bound to the adsorbed
metals (Knox, 1978). The rate of the adsorption process is slow at room
temperature, but is accelerated by high temperature (McAtee and Smith,
1969; Skelly and Dieball, 1969; Knox, 1978).
Thus, in a chrome- or ferrochrome-lignosulfonate drilling mud
that has been used for an extended period of time at moderate down-hole
temperatures, much of the chromium will be associated with the clay portion.
However, significant amounts of chromium may remain in the aqueous phase,
presumably still complexed with soluble lignosulfonate (Table 8). Liss et
al., (1980) reported 9' - 45 mg/1 total chromium in the liquid phase of
used drilling fluid samples containing 200-850 mg/kg total particulate
chromium. Similar results have been obtained for other used chrome ligno-
sulfonate drilling muds by Neff et al. (1980) and Page et al. (1980).
Concentrations in used drilling muds of cadmium, copper, mercury,
lead and zinc are extremely variable (Table 6; Appendix I, Tables 2a - 9a).
Most of these metals are present as trace impurities in several major drill-
ing mud ingredients (Table 7).
Cadmium and mercury are of particular concern because of their
high toxicity to marine organisms and potential for transfer through aquatic
food chains to Man (Hiatt and Huff, 1975; Calabrese et al., 1977). These
metals are present in drilling fluids almost exclusively as trace contaminants
of barite. As can be seen in Table 7, ba.rite from different sources may contain
-------
28
Table 8. Dissolved (aqueous phase) metal concentrations in drilling
mud samples taken at several depths from the Imperial Oil
Company, ADGO F-28 well offshore the MacKenzie River Delta,
Beaufort Sea, Canadian Arctic. All values are in rug/liter
(From Beak Consultants, 1974).
Metal
Cadmium
Chromium
Copper
Iron
Lead
Zinc
Sodium
Potassium
Calcium
Magnesium
4,000
<0.05
3.6
<0.05
2.8
<0.25
0.06
3,800
2,700
90
34
Depth
6,000
<0.05
6.1
<0.05
5.3
<0.25
0.30
1,060
150
3.7
2.1
(feet)
7,000
<0.05
3.5
<0.05
-
<0.25
0.15
780
70
2.5
1.2
8,000
<0.05
6.0
<0.05
5.3
<0.25
0.18
900
70
2.6
1.9
-------
29
0.5 - 32 ppm cadmium and 0.13 to 28 ppm mercury. These and other metal
contaminants of barite are present almost exclusively as extremely in-
soluble sulfides (Kramer et al., 1980). As a result, very little of these
metals appears in the soluble or aqueous phase (Table 8). Kramer equili-
brated 1 g each of low- and high-trace metal barite with 100 g seawater
and measured soluble metal concentrations in 0.45u-filterecl samples of
the water (Table 9). In samples equilibrated with low trace metal bedded
barite, all aqueous metal concentrations were at or below normal oceanic
levels. In seawater equilibrated with high trace metal vein barite, con-
centrations of soluble mercury, lead and zinc were significantly higher
than open ocean concentrations. Addition of bentonite clay (a normal in-
gredient of drilling muds) reduced aqueous mercury concentrations to below
oceanic levels.
Mercuric sulfide and most other metalic sulfides are quite
immobile once deposited in bottom sediment because of their low aqueous
solubility. Although mercury from mercuric sulfide can be methylated to .
highly mobile and toxic methyl mercury compounds by sediment bacteria,
speed and efficiency of this transformation in only 10~^ times that of
methylation of ionic Hg+2 (Fagerstrom and Jernelov, 1971). Because of the
low concentration of mercury in most drilling mud samples, and its presence
there primarily in the form of insoluble mercuric sulfide, discharge of
drilling muds to the ocean does not appear to represent a significant
route of entry of mobile mercury compounds to the marine environment.
Bentonite clay and chrome lignosulfonates may contribute small
amounts of cadmium, copper, lead, and zinc to drilling muds (Table 6).
In addition, pipe thread compound (pipe dope) and drill collar dope
(used to lubricate the threads where two sections of drill pipe or pipe
and drill collar are joined together and make the union electrically con-
ducting) may contain high concentrations of metallic lead, zinc and
copper. According to Ayers et al. (1980a), drill pipe dope contains 15
percent copper and 7 percent lead. Drill collar dope contains 35 percent
zinc, 20 percent lead and 7 percent copper. As much as 250 kg pipe dope and
160 kg drill collar dope may be used during drilling of a single well.
Although these dopes are not added directly to the drill mud, small
-------
30
Table 9. Concentrations of heavy metals in solution in seawater equilibrated with
solid barite (barium sulfate) containing low or high concentrations of
trace metals. Concentrations are in yg/kg (parts per billion).
(From Kramer et a!., 1980).
Metal
Sample
Ocean seawater^
Hg
0.03
Pb Zn
~1 <1
Pd
0.03
Cu
<2
Ni As
~1 ~1
Low trace metal
Bedded barite <0.01-0.14* <1-1 <0.1 <0.1-1.4 <1-1.9 2-5 <0.2
Vein barite <0.01-0.32* 50-200 7-290 0.4-5 1-4.3 6.6-10 <0.2
1. From Hogdahl (1963). The trace elements in the ocean. A bibliographic
compilation. Central Inst. Indust. Res. Blindern, Oslo, Norway.
* with bentonite <0.01-0.01.
-------
31
amounts get into it. Metals from this source are in the form of fine
metallic granules and are very unevenly distributed in the mud. Finally,
inorganic zinc salts as zinc carbonate, zinc chromate, or zinc sulfonate
may be added to drilling muds as H2 S scavengers. In such cases zinc is
precipitated as zinc sulfide.
A few analyses for arsenic, nickel, vanadium, and manganese have
been performed on drilling muds and mud ingredients (Tables 6 and 7).
Arsenic may be present in drilling muds at concentrations near 2 mg/kg,
nickel at 4-30 mg/kg and vanadium at 14 - 28 mg/kg. Manganese may occur
at much higher concentrations (290 - 400 mg/kg). Arsenic, nickel, and
possibly also vanadium are introduced primarily with barite. Chrome ligno-
sulfonate may contain high concentrations of manganese. Marine sediments
also typically contain high concentrations of manganese.
Concentrations of iron are high in most drilling mud samples
(Table 6). Concentrations in excess of 10,000 mg/kg (1%) appear common.
Bentonite and several other clays are 2-4 percent iron by weight (Ayers
et al., 1980a). Of course ferrochrome- and iron-lignosulfonates contain
high concentrations of iron.
Other Characteristics
Most used offshore drilling fluids have an alkaline pH due to
added NaOH and Na2C03- Typical pH is between 8 and 1.1 (see Appendix I,
Tables 2a - 8a). Mud weight or density may vary between 9 and 18 Ib. per
gallon (1.07 to 2.15 kg/liter). Chemical oxygen demand of whole used mud
is often in the range of 1,000 - 20,000 mg/liter and seems to be related to
concentrations of organic compounds Jin the mud (Beak Cons., 1974).
Total organic carbon concentration may vary from 30 to 10,000
mg/1 mud depending on original mud composition (Strosher, 1980). About
three-fourths of the organic carbon in used drilling muds is attributable
to unaltered mud additives. Petroleum hydrocarbons, .either added inten-
tionally as diesel oil or asphalt or from strata penetrated by the drill
may account for 5-10 percent of the TOC. Chrome lignosulfonate under-
goes some decomposition and degradation under conditions of high temperature,
alkalinity and pressure characteristic of a deep hole (Carney and Harris,
-------
32
1975; Knox, 1976). Thermal degradation of chrome lignosulfonate is
accelerated at temperatures above about 330ฐF (165ฐC) (Simpson, 1967).
The lignin of chrome lignosulfonate is a polymer of an alcohol-substituted
phenyl propane and its degradation products may include phenolic com-
pounds such as vanillan and isoeugenol (Carney and Harris, 1975). Other
organic compounds added to some muds (lignite, carboxymethylcellulose,
starch, organic dispersants, emulsifiers, lubricants, etc.) may be subject
to temperature/pressure degradation and lead to production of .a variety of
organic byproducts. The important conclusion to draw from this discussion
is that drilling muds change in chemical composition and physical properties
during normal usage. A newly-formulated or laboratory-mixed "synthetic"
mud will be quite different physically and chemically from a drilling mud
that actually has been used for an extended period of time in an offshore
drilling operation. By inference, toxicity of newly-formulated or synthetic
and real used drilling muds can be expected to be quite different.
-------
33
FATE OF DRILLING FLUIDS DISCHARGED TO THE OCEAN
Discharge Practices
During normal exploratory drilling operations several drilling
mud and cuttings-related effluents are discharged to the oceans. Typical
discharges and discharge rates from an offshore platform are summarized
in Table 10. The only more-or-less continuous discharge during normal
drilling is from the shale shakers which remove drill cuttings from the
mud that has returned from down-hole. Although most of the mud is removed
from the cuttings during passage through the shale shakers, discharged
cuttings may contain 5-10 percent drilling mud. The amount of drill
cuttings produced per day depends on the vertical distance drilled that
day, and the diameter of the drilled hole. Hole size decreases with in-
creasing depth drilled (Monaghan et al., 1977; Ray, 1979). A typical bore
hole may be 36 inches in diameter for the first 500 feet and diameter may
be reduced at about five depth intervals to about 6.5 inches at 15,000 -
20,000 feet. The hole is lined with steel casing which is held in place
with cement injected into the annulus between the casing pipe and the
hole wall. During emplacement and cementing of casing, drilling is
stopped. The drill may have to be changed every 20-100 hours of opera-
tion. To do this the complete drill string must be removed from the hole,
which may take 12 hours. Drilling may have to be stopped temporarily if
problems are encountered or for normal operations like testing, logging,
and well surveys. Drilling may actually occur only one-third to one-half
the time during'a two-three month drilling operation (Ray, 1979; Ray and
Meek, 1980).
Therefore, drilling and as a result cuttings discharge are not
continuous. In addition, volume of cuttings discharged per day while
drilling is going on decreases as the depth of the well increases and
casing diameter decreases. Temporal pattern of a typical cuttings dis-
charge is shown in Figures 2 and 3 (Ray and Meek, 1980). Large volumes of
cuttings are released directly to the sea floor without being returned to
the rig during the jetting and spudding in of the surface hole.- After returns
to the rig are established, rate of cuttings discharge from the shale
shakers decreases almost logarithmically with time during the remainder of
-------
34
o
m
o
600
<2 Q
S ง 500
0 S
Z ^
p -J 40ฐ
i i
U 300
200
100
o
December
f
-
-
n
'
I
?
i
i
7
^
/i
%
I
i
IT
I
1
r
1
4
January
rf
\
21
g
!8 1
I
\
1
BULK MUD DISCHARGES Ev^|
. - CUTTINGS DISCHARGED FROM
PLATFORM . E^4 "
' * CUTTINGS RELEASED AT t^j ,
SEA FLOOR S2^3
_
'.
';
r 14 21 1 7 14 21 28
February | March
1
1
| April
Figure 3. Volumes of bulk drilling mud and cuttings discharges each day
during drilling of an exploratory well on Tanner Bank, California
(From Ray and Meek, 1980).
-------
35
the drilling operation. For the Tanner Bank, California exploratory well
studied by Ecomar (1978) and Ray and Meek (1980), total volume of cuttings
produced and discharged during drilling to 3,419 meters (11,200 ft.) was
estimated to be 11,138 ft3 (315 m3). This value is in reasonable agreement
with estimated typical cuttings discharge of 334 m3 from a 10,000 foot well
(Shinn, 1974).
Rate of accumulation of waste effluents by the other solids control
equipment in the drilling mud system (desander, desilter, centrifuge, sand
trap, and sample trap; Figure 1, Table 10) will depend in large part on rate
of drill cuttings production. Thus, rate of discharge from the total solids
control system will decrease with time during the drilling operation (Figure
4; Ayers et al., 1980a). During the approximately five months required to
drill an exploratory well to 4,970 meters (16,280 ft.) in NJ 18-3 Block 684
pf the Mid-Atlantic outer continental shejf,'.. approximately 268,800 gallons
of solids control equipment effluents were discharged to the ocean. This
effluent contained 863 metric tons of solids, 41 percent of which came from
the shale shakers, 40 percent from the desander, and 19 percent from the
mud cleaners. Most of this was drill cuttings. Perhaps 43 metric tons
was drilling mud.
Whole used drilling mud is discharged intentionally, in bulk
quantities several times during drilling operations. Some mud may be dis-
charged to make space in the mud tanks for addition of water or mud ingre-
dients to change mud properties. If mud is pumped out of the hole for
emplacement and cementing of casing, there may not be enough capacity in
the mud tanks and the excess is discharged. Changeover of mud programs
(e.g., from seawater lignosulfonate mud to freshwater lignosulfonate mud)
may require bulk discharge of a large volume of mud. Volume of individual
bulk mud discharges during normal drilling operations usually is in the
range of 100 - 300 barrels (4,200 - 12,600 gal.) (Ray, 1979), but may exceed
2,000 barrels (84,000 gal.) for a major change of mud program. A single bulk
discharge might last for 15 minutes to two hours. Bulk discharges may take
place only a few times during drilling (Figure 3; Ray and Meek, 1980) or al-
most daily (Figure 5; Ayers et al., 1980.a). More frequent bulk discharges
are required if dilution is used to control solids build-up in the mud, as
-------
Table 10. Summary of drilling mud discharges frcm an exploratory drilling platform in Lower Cook Inlet,
Alaska. Volumes have been converted to gallons according to 1 barrel = 42 gallons (From
Houghton et al., 1980).
Source or Type
of Discharge
Volumetric
Composition (%)
Discharge
Frequency
Discharge
Rate
Estimated Maximum
Daily Discharge
Continuous discharges
from:
Shale Shakers
Desander
Des ilter
Centrifuge
Sand Trap
Sample Trap
Bulk Discharges
from:
Cementing
Dilution
Rheology
End of Drilling
50% Cuttings
7.5% Drilling Mud Solids
42.5% Water
25% Sand
75% Water
22.5% Silt
2.5% Drilling Mud Solids
75% Water
1% Drilling Mud Solids
99% Water
20% Sand
7.5% Drilling Mud Solids
72.5% Water
15% Drilling Mud Solids
and Cuttings
85% Water
10-15% Drilling Mud Solids
85 - 90% Water
10-15% Drilling Mud Solids
85 - 90% Water
10-15% Drilling Mud Solids
85 - 90.% Water
Continuous during
drilling
2-3 hr/day during
drilling
2-3 hr/day during
drilling
1-3 hr/day as
required
Every 2-3 days
for 2-10 min1
Every 2-3 days
.for 5-10min'
3-6 times
per well '
Less than 3
per well1
Once per well1
42-84 gal/hr
126 gal/hr
672-714 gal/hr
1,260 gal/hr
4,000 gal in
2-10 min
630 gal/hr
420 gal /min
for up to 20 min
29,400 gal/hr
(max 8,400 gal)
29,400 gal/hr
(up to 3 hr)
1,008 - 2,016 gal
252 - 378 gal
1,344 - 2,142 gal
1,260 - 3,780 gal
4,000 gal
52.5 - 105 gal
8,400 gal
8,400 gal
88,200 gal
CO
01
1. Not discharged during drilling.
-------
0' ' ' Tl I I HfB" ' KIRa;aaW?rKBWlfflrfiiaiiffiiii*i''* ' ซBซaBigB^eigpaM ijg i yiqa asunem i ga I I I I I I I I I I I I I I I i n
I 4 7 10 11 16 II 22 2S 21 )1 1 6 I 12 1] II 21 II 27 2 S I 11 14 17 20 23 26 29 .1 4 7 10 13 16 1ป ปl 25 21 1 4 7 10 II ซ II 22 25 21 11 I i 9 12 II II 21 24 27 10 I ( 9 12 IS II "
6000
5000
4000
C/J
CO
3000
2000
1000
GO
JAN ("Mm) FEB (3000m) MAR (3830m) APRIL (ซ"0m) MAY <ซ">m) JUNE JULY
TIME
Figure 4. Daily and cumulative volume of solids control equipment discharges
(mainly cuttings and water) during exploratory drilling in the
Baltimore Canyon off New Jersey (From Ayers et al., 1980a).
-------
2400
H2000
-j 1600
01 mm*n i i t.-y/-i^-^JTti^<^iya^iJTt^ปl^tK^rgTtJ!.^^^LJKjj'l^'^""^M^f*n^aaMa | BปBBTgr.at;-!i5*.!r=iir-ci!Hi i I I I ewj?vifi Ktt i tra i n
1 4 7 10 13 16 19 It Kit 11 3 6 9 1} IS II 21 24 27 2 t I II 14 II M 11 It It 1 4 7 tl 1} It 11 71 It M I 47 II It II II 12 ป II Jl 1 I I 12 II II 21 24 27 M 1 i ป 12 16 II U
CO
z
o
1200
UJ
JAN (1200m) FEB (3000m) MAR (3830m) ' APRIL ซซ0m) MAY (ซซ0m) JUNE
TIME
JULY
Figure 5. Daily and cumulative volume of total solids discharges (bulk mud
discharges plus solids control equipment discharges) during explor-
atory drilling in the Baltimore Canyon off New Jersey (From Ayers
et al., 1980a).
GO
OO
-------
39
was the case in the Mid-Atlantic DCS exploratory program described by Ayers
et al. (1980a).
At the end of the drilling operation, any drilling mud remaining
in the mud system usually is discharged to the ocean. Volume of this bulk
discharge will depend somewhat on volume of mud tanks and depth of hole
(the hole may contain more mud that the mud tanks). It is usually in the
range of 1,000 - 2,500 barrels (42,000 - 105,000 gal.) (Ray, 1979). Several
bulk mud discharges may take place at the end of drilling, each lasting
one to several hours (Figures 3 and 5).
In the two drilling operations discussed here, total volumes of
mud discharged to the ocean during the entire drilling operations were
2,460 barrels (103,320 gal.: Tanner Bank; Ray and Meek, 1980) and 30,800
barrels (1,293,600 gal.: Mid-Atlantic OCS; Ayers et al., 1980$). In the
latter study, total solids in the discharged drilling mud amounted to
1,287 metric tons. The values are fairly representative of the amounts
of mud discharged during normal offshore drilling operations.
Design of mud and cuttings discharge systems varies from one
rig to another (Ray, 1979). Discharge may be directly from the platform
surface with free-fall to the .water. A flexible hose may be rigged to
carry the mud and cuttings to the water surface. Alternatively, shunt pipes
12 to 18 inches in diameter may be an integral part of the rig. The shunt
pipe may discharge mud and cuttings anywhere from near the surface to just
above the bottom. Some consideration should be given to designing a mud/
cuttings shunt pipe system that would maximize dilution of effluents with
ambient seawater before they are released to the ocean. ,
Dispersion and Dilution in the Hater Column
Drilling mud is a slurry of solid particles of different sizes
and densities in water. Various mud additives may be water-soluble,
colloidal, or particulate. Clays, silt and cuttings have a specific
gravity of about 2.6 g/cc, while barite has a specific gravity of about
4.2 - 4.5 g/cc. As a result of this physical/chemical heterogeneity, upon
discharge to the ocean, drilling mud undergoes substantial and rapid
fractionation. Drill mud discharged from a submerged, discharge pipe can
-------
40
be thought of as going through three distinct phases: convective descent
of the jet of material, dynamic collapse, and passive diffusion (Figure 6;
Brandsma et al., 1980). In the jet phase, the plume descends rapidly,
entraining low-density particles and bending.toward the direction of current
flow. Dynamic collapse begins when the plume encounters the level of neutral
buoyancy or the sea bottom. Vertical descent is retarded. The plume flattens
in the vertical axis and broadens in the horizontal axis. Lighter particles
and soluble materials may begin to ascend, while heavier particles settle
on the bottom. Even in the jet phase, the larger denser particles may
leave the plume and descend at a more acute angle than the plume itself.
The diffusion phase occurs when the kinetic energy imparted to the plume at
discharge is used up and movement of the plume is controlled by convection
and turbulence of the ambient medium and by simple diffusion and gravitational
.settling of the mud components. During this entire process, the mud plume is
being diluted continuously with seawater and by settling to the bottom of
denser fractions. A critical determinant of the impact of discharged drill-
ing mud on the water column and its biota is the rate and extent of this
dispersion/dilution process.
Several detailed investigations have been performed of rate of
dispersion and dilution of drilling muds discharged at different rates
from'offshore platforms in the Atlantic, Pacific and Gulf of Mexico. Ray
and Shinn (1975) observed that drilling mud and cuttings discharged at
35 feet below the surface from an oil rig in 245 feet of water in the Gulf
of Mexico, fractionated rapidly. Finer, low density particulates rose
vertically, spread horizontally, and were dispersed down-current. Heavy
and larger particulates fell almost straight down and accumulated on the
bottom under the discharge pipe. Of several water-column parameters mea-
sured in an effort to quantify dispersion and dilution of the drilling mud
plume, only total suspended solids showed elevated values near the discharge
point. Elevated total suspended solids concentrations were detected about
90 feet east and west of the platform, but not at greater distances, during
mud/cuttings discharge. A mathematical dilution model constructed by Ray
and Shinn (1975) predicted a drilling mud dilution of 100 to 1 at 50 feet
from the discharge point and a 1,000 to 1 dilution at a little more than
1,000 feet.
-------
Figure &. Idealized jet discharge described by mathematical
model. Cross-sections are shown at three stages
of the plume. A heavy class of particles is
depicted settling out of the plume at an early
stage. Lighter particles are shown settling
during the collapse phase. Very fine particles
are shown leaving the plume shortly after dis-
charge and remaining near the surface to form the
visible plume. (From Brandsma et al., 1980).
ฃ':*'?'.'-, \; '.'' ^f-<^_
CON VECT; v E.DEscerrr
PASSIVE DIFFUSION
/v'vi :>ฃ>;:
v.^ .._..'*..ซ.
ENCOUNTER
NEUTRAL
BUOYANCY
DIFFUSIVE SPREADING
GREATER THAN
DYNAMIC SPREADING
-------
42
Zingula (1975) obtained roughly similar results in an investiga-
tion of drilling mud discharges from a platform in Timbalier Bay, Louisiana.
Total suspended solids concentrations reached background values 660 feet
down-current from the discharge pipe. At 300 feet, total suspended solids
concentration was 40 mg/1 compared to a background concentration of about
5 mg/1. Drilling mud/cuttings collected directly below the shale shaker
had a total suspended solids concentration of about 350,000 mg/1, while
.water at the exit of the discharge pipe had a total suspended solids con-
centration of 278 mg/1. This indicates that drilling mjjd may be diluted
approximately 1,000-fold in the discharge pipe before actual discharge to
the ocean.
A detailed drilling mud and cuttings monitoring study was performed
during exploratory drilling from a semi-submersible drilling platform on
Tanner Bank in the Pacific Ocean 161 km west of Los Angeles, California
(Ecomar, 1978; Ray and Meek, 1980). Physical and chemical characteristics
of mud plumes were monitored during several normal mud discharges (Table 11).
Discharges A and B were at a rate of 10 bbb/hr (420/gal/hr) into
seawater moving at a speed of 11.8 and 45.2 cm/sec, respectively. The nearly
four-fold difference in current speed had little effect on rate of plume
dilution as measured by any of several physical or chemical parameters. As
expected, there was a tendency for near-field dilution to be more rapid
under high than under low current speeds. In both cases however, initial
dilutions were extremely high within 3':m of ithe discharge pipe, ranging from
500:1 to almost 1,000:1. These initial dilution rates are based on a;.
measured suspended solids concentration of 250,000 mg/1 in the drilling mud
entering the discharge pipe on the platform. Total suspended solids con-
centrations approached background values within about 200 m of the discharge.
Particulate heavy metals concentrations in the plumes approached background
within 150 m of the discharge.
In discharge D, initial dilution in the discharge pipe (250,000
mg/1 to 43.04 mg/1) was even greater than in the earlier studies. Suspended
solids concentration had reached background by 90 meters down-current. The
heterogeneous nature of drilling mud plumes is indicated by the manner in
-------
Table 11. Summary of drilling mud discharge plume dsta from several metered drilling mud discharges from an exploratory drilling platform
on Tanner Bank off Southern California. Heavy metals concentrations are for the solid phase alone (From Ray and Meen, 1980).
Discharge Rate
10 bbl/hr
10 bbl/hr
12 bbl/hr
20 bbl/hr
754 bbl/hr
Station
Al
A2
A3
A4
A-Control
Bl
B2
B3
B4
B-Control
Dl
02
D3
D4
05
06
El
E2
E3
E4
E5
E6
Gl
G2
G3
G4
G5
G6
G-Control
Distance(M)1
0
105
155
450
91
0
76
145
440
76
0
90
130
175
250
350
0
55
140
200
275
310
0
74
' 500
625
800
1,000
373
Depth(M)2
12
12
8
23
15
12
15
15
5
15
12
10
. 15
15
20
10
12
10
5
10
15
5
12
10
5
20
20
25
15
Current Speed
(cm/sec) Transmittance(%)
11.8
49.1
62.8
. 77.1
83.4
45.2
66.7
65.7
48.4
82.0
29.8
46.0
51.6
74.6
77.5
83.3
2.2
28.4
41.3
40.5
63.4
55.6
15.9
0.0
19.3
80.8
23.7
10.9
94.8
Suspended Solids
(mg/1)
499
5.20
2.03
1.79
1.54
252
1.95
1.17
1.01
0.829
43.04
1.59
2.20
2.11
1.33
1.51
279
2.74
1.81
2.18
1.01
1.56
328
25.2
4.04 '
1.10
4.73
0.563
0.814
Barium
(ng/i)
23,560
103
46.6
37.8
13.5
7,780
22.2
34.3
38.3
62.3
1,033
67.6
112
52
17.1
21.8
3,860
75.5
39.5
49.3
26
35.6
12,700
575
146
47.2
111
26.2
21.9
Chromium
tog/1)
824
4.07
0.859
0.865
0.430
346
1.44
0.928
0.707
0.443
43.50
1.90
2.31
2.23
1.01
1.09
238
1.97
1.07
2.42
0.534
1.62
917
13.5
16.4
0.528
7.37
0.916
0.481
Lead
(WQ/1)
38
0.395
0.398
0.477
0.373
17.6
0.490
0.232
0.325
0.429
263
0.424
0.404
1.011
0.211
0.194
5.03
0.249
0.337
0.298
0.237
0.400
40.5
2.74
0.880
0.455
4.4
0.116
0.223
1. Meters down stream from the discharge; 2. Depth is point of maximum plume density (determined by transmissometry where samples were taken.
-------
44
which values for water quality parameters fluctuate up and down with dis-
tance from the discharge.
When rate of drilling mud discharge was increased to 20 bbl/hr
(840 gal/hr), there was little change in the rate of mud dilution. Back-
ground concentrations of total suspended solids were approached within 55-
140 m of the discharge pipe. -Rate of heavy metal dilution was similar to
that of suspended solids.
Drilling mud dilution and dispersion were much less rapid during a
high rate mud discharge of 754 bbl/hr (31,668 gal/hr). Background con-
centrations of total suspended solids were not approached until 800-1,000
m from the discharge. Particulate heavy metals also reached background
at about 1,000 m. .
Transmissometry values (% transmittance) tended to return to
normal control or background values more slowly than other water column
parameters used to monitor drilling mud dilution. Percent transmittance,
a measure of the transparency of water, is perhaps the best measure..of.
the dilution of the very fine clay-sized particulate fraction of the mud
and cuttings. During low-rate discharges, percent transmittance approached
background within 275-450 meters of the discharge in most cases. During
the high rate mud discharge, percent transmittance was still very low 1,000 m
from the discharge. The results suggest that mixing and dilution of the very
fine clay-size particulate fraction of mud and cuttings is slower than dilution
of coarser, denser fractions, the latter containing most of the particulate
metals of concern.
Rapid dilution of drill mud in the discharge pipe before the mud
exited to the ocean was attributed^- to oscillatory in-and out-flux of water
in the vertically-mounted discharge pipe due to wave action. Discharge pipe
design should be modified to maximize this pre-discharge dilution of drilling
mud.
Ayers et al. (1980b) studied dilution and fate of two experimental
discharges of a typical chrome lignosulfonate-clay mud (bulk density 17.4 lb/
gal) from an exploratory rig in 23 meters of water in the Gulf of Mexico.
In the first, 250 barrels of mud were discharged at a rate of 275 bbl/hr
-------
45
(11,550 gal/hr). In the second 389 barrels of mud were discharged at a
rate of 1,000 bbl/hr (42,000 gal/hr). These high discharge rates are
typical of those used at the end of a drilling operation to empty the mud
tanks before moving the platform to a new location.
During both discharges, the mud formed two plumes. The lower
plume, containing most of the .discharged material and especially the denser,
coarser particulate fractions, descended quickly to the sea floor. As the
lower plume descended, an upper, near surface plume was generated by tur-
bulent mixing of the lower plume with seawater. The upper plume containing
much of the fine clay-sized low density particulates, persisted longer in
the water column than the lower plume, and was carried away from the dis-
charge by water currents.
During both discharges, total suspended solids concentrations de-
clined very rapidly with distance from the discharge (Table 12). During the
250 bbl/hr discharge, suspended solids concentration reached background
within about 364 meters of the discharge. In the 1,000 bbl/hr discharge
the background concentration of suspended solids was reached in about 878
meters.
Percent transmittance values rose slowly with distance from the
discharge. Background values for percent transmittance were reached at
625 and 1,470 meters during the 250 and 1,000 bbl/hr discharged, respectively.
Again this indicates the slower rate of dilution and dispersion of fine clay-
sized particulates than coarser particles in the water column. While both
fine and coarse particulates contribute to both total suspended solids con-
centration and percent transmittance values, the coarser particles make up
the bulk of the weight of suspended solids, while the finer particles con-
tribute more than the coarser particles to the decrease in water transparency.
Drilling mud plumes become progressively more dilute as they are
transported away from the discharge point by water currents. A quantitative
parameter extremely useful in assessing potential environmental impacts of
drilling mud plumes is time required for water quality parameters in the
plume to reach background values. If values for these parameters are
plotted graphically versus transport time (distance from discharge point
-------
46
Table 12. Dilution and dispersion of two drilling mud plumes produced by high
rate high volume discharges of used chrome lignosulfonate drilling
mud from an offshore exploratory platform in the Gulf of Mexico
(From Ayers et al., 1980b).
Discharge Rate
Distance From
Source (Meters)
Depth
(Meters)1
Suspended
Solids
(mg/1)
Transmittance(%)
275 bbl/hr
(250 bbl discharged)
1,000 bblhr
0 (Whole Mud)
6
45
138
250
364
625
Background
0 (Whole Mud)
45
51
152
375
498
111
878
957
1,470
1,550
Background
8
11
9
9
9
9
11
12
11
16
14
13
2
12
11
9
1,430,000
14,800
34
8.5
7.0
1.2
0.9
0.3-1.9
1,430,000
855
727
.5
,1
50.
24.
8.6
4.1
1.2
0.83
2.2
1.1
0.4-1.1
2
56
48
37
71
76-85
0
0
2
4
23
21
71
76
82
82
80-87
1. Depth at which highest plume concentration was found.
-------
47
divided by current speed) a curve asymptotically approaching the back-
ground value is obtained. This curve defines the rate of dilution or change
of the water quality parameter. Rates of dilution of .total barium, aluminum
and chromium during the two mud discharges described by Ayers et al. (1980b)
are summarized in Figures 7, 8 and 9. During the 250 bbl/hr discharge
barium, aluminum (a tracer for the clay fraction), and chromium reached
background values in about 70 minutes, 30 - 50 minutes, and 20 - 55 minutes,
respectively. Dilution of the metals to background concentrations in the
water column took longer during the 1,000 bbl/hr discharge. Times required
were about 110 minutes, 90 - 110 minutes, and 90 - 100 minutes for barium,
aluminum and chromium, respectively. Relationship between rate of drilling
mud discharge and rate of dilution to background is depicted graphically in
Figure 10.
This study shows that during high rate discharge of drilling muds
to the ocean, dilution of mud solids to background concentrations occurs
within about 1,000 meters down-current from the discharge point and is
accomplished in less than two hours.
Somewhat similar results were obtained during an investigation
around an offshore rig in the Mid-Atlantic outer continental shelf about 156
km east of Atlantic City, New Jersey in 120 meters of water (Ayers et al.,
1980a). During a 500 bbl/hr discharge, the Tower, rapidly descending plume
containing the bulk of the discharge, contained 1,195 mg/1 total suspended
solids 15 meters down-current from the discharge in 24 meters of water.
The upper plume was much more dilute. In the upper plume, background con-
centrations of suspended solids were reached at about 350 meters during a
500 bbl/hr mud discharge and at 600 meters during a 275 bbl/hr discharge.
During the 500 bbl/hr test, the plume flattened noticeably near the surface
and was not detectable below about five meters depth within 150 meters
down-current from the discharge. During the 275 bbl/hr test, the plume
center remained ten to fifteen meters deep for a distance of about 600
meters from the discharge. As in the Gul.fof Mexico -study, values for per-
cent transmittance reached background-at a greater distance from the dis-
charge than the distance at which suspended solids concentration reached
background.
-------
4
LOG .
OF J
BARIUM
CONCENTRATION 2
(mg/l)
1
0
-1
-2
WHOLE MUD BARIUM CONCENTRATION
m = 1000 BBL/HR TEST
ฉ =275 BBL/HR TEST
CONCENTRATION
I
10
_] 1 1 1 1_JL_
20 30 40 50 60 70 80
TRANSPORT TIME (MINUTES)
I
I
CO
100 110 120
Figure 7. Decline in maximum total barium concentration in drilling mud
plumes with transport time (distance from discharge/current speed)
during two high-rate bulk drilling mud discharges (From Ayers et al.,
1980b).
-------
49
LOG
OF
ALUMINUM
CONCENTRATION
(mg/l)
4
3
2
1
0
-1
-2
-3
WHOLE MUD ALUMINUM CONCENTRATION
m = 1000 BBL/HR TEST
O = 275 BBL/HR TEST
CONTROL
CONCENTRATION
I I I I L_J I J I_J L__i
10 20 30 40 50 60 70 80 90 100 110 120
TRANSPORT TlfciE (MINUTES)
Figure 8. Decline in maximum total aluminum concentration (a marker of the
clay fraction) in drilling mud plumes with transport time during
two high-rate bulk drilling mud discharges (From Avers et al.,
1980b).
-------
~l
6
5
LOG
OF
'
CONCENTRATION
-1
-2
-3
-4.0
WHOLE MUD CHROMIUM CONCENTRATION
1000 BBL/HR TEST
275 BBL/HR TEST
CONCENTRATION
1
I
_| I L I I !._ I 1.1 L_
0 10 20 30 40 50 60 70 80 90 100 110
, TRANSPORT TIME (MINUTES)
Figure 9. Decline in maximum total chromium concentration in drilling mud
plumes with transport time during two high-rate bulk drilling mud
discharges (From Ayers et al., 1980b).
en
o
120
-------
s
uT
120
110
100
90
80
70
60
50
40
30
20
10
0
"o
a
o THIS STUDY
a ECOMAR, 1978
100
200
300
400
500
600
700
800
900
1000
1100
DISCHARGE RATE, BBL/HR
Figure 10. Relationship between bulk drilling mud discharge rate and transport
time (distance from discharge/current speed) required for solids
concentration in the drilling mud plume to reach background (From
Ayers et al., 1980b).
-------
52
Houghton et al. (1980b) measured dilution and dispersion of two
small and one continuous discharge of mud and cuttings from a semi-submersible
drilling vessel in Cook Inlet, Alaska. Dye dilution, using Rhodamine WT, and
transmissometry were used to track the plume. Turbulence created by the strong
water currents moving around the drilling vessel caused very rapid dilution of
the drilling mud plume. In the'two small bulk discharges a dilution of 2.2 X
104 was observed about 800 meters down-current from the discharge, the plume
did not descend deeper than about 23 meters. _
During the continuous mud discharge also, the mud plume did not
descend deeper than 23 - 30 meters. The dye was diluted more than 104-fold
within 100 meters and within a few minutes of the discharge. These rapid
dilutions were caused by the convective mixing resulting from the fast-
moving and complex three dimensional flow-field created by the hull of the
drilling vessel.
During discharge of used <'d rilling mud as a heavy spray to the sur-
face of the ocean from a drilling rig in the Gulf of Mexico, suspended
solids concentration in7 the surface water was about 10-fold above background
about 200 m down-current from the rig (Trocine et al., 1981; Trefry et al.,
1981). Estimated dilution of drilling mud at this point was 0.5 x 106-fold
compared to solids concentration of whole drilling mud. A rapidly moving
surface current above a distinct pycnocline restricted vertical advection
of the plume somewhat. Thirteen hours after termination of the discharge,
total suspended solids concentrations had increased to well above background
below the pycnocline at a station 800 meters from the rig (from about 100
to about 200 ug/1 suspended solids). Sixteen hours after the discharge, at
a distance of 3.2 km from the rig, the particulates were concentrated in a
15 meter thick nephloid layer just above the bottom. The nephloid layer
was composed primarily by resuspended sediments.
Concentrations of particulate metals, chromium, iron, and barium,
showed a temporal/spatial distribution similar to that of suspended solids
concentration. Barium penetrated the pycnocline into deeper water most
rapidly, followed by iron, then chromium. This reflects the differences
in density of the particles with.which these metals were associated.
-------
53
Background concentrations of participate Cr, Ba and Fe in the
ocean near the rig site were less than 4, 30, and 200 .ng/1, respectively.
One km down-current from the rig, ten hours after termination of the dis-
charge, particulate chromium concentrations were from 1 to 11 ng/1.
Particulate matter iron concentrations were about 100 ,ng/l in the surface
waters, and rose to 1,800 n.g/1 10 meters above the bottom due to the pre-
sence of a nephloid layer composed of resuspended sediment. Particulate
barium concentrations were uniform throughout the water column at 80 jig/1,
somewhat elevated above the 30 jng/1 background values. Thus, using highly
refined and sensitive analytical techniques, the authors were able to detect
remnants of the mud plume 10 hours after and 1 km away from the discharge.
These investigations also demonstrated the usefulness of particulate barium
as a tracer of drilling mud plumes.
The investigations reviewed above are all ..in reasonable agreement
in showing that drilling fluids discharged to the oceans are diluted and
dispersed very rapidly, both spatially and temporally. Several thousand-
fold dilutions are nearly always encountered within a few hundred meters
down-current of the discharge pipe. Background conditions (depending on
the water quality parameters measured and sensitivity of analytical techni-
que) are usually approached within one-thousand meters of the discharge,
though traces of the discharge can still be detected by the most sensitive
techniques.
Because of the intermittent nature and variable rate of drilling
mud and cuttings discharges from offshore platforms, and the rapid dilution
of discharged drilling mud, it is apparent that drilling mud concentration
in the water column, with respect either to a moving water mass or a geo-
graphic point, will never remain high for a long period of time.
Deposition of Drilling Muds in Bottom Sediments
Virtually all the solids and some of the soluble components
(through adsorption to particulates) of drilling muds eventually are de-
posited in bottom sediments adjacent to and down-current from the drilling
platform. Points of concern about such deposition are that mud and cuttings
may accumulate on the bottom to depths that would physically smother benthic
-------
54
epi- and infaunal organisms, that such deposition might change sediment
texture or chemistry rendering the substrate unsuitable for certain species
of marine organisms, that metals and other potentially toxic mud ingredients
might accumulate in sediments, either killing benthic organisms or serving
as a source of contamination of marine food webs. As a result of these
concerns, much research has been performed in recent years.on the deposition
and accumulation of drilling muds and in particular mud-associated metals
in sediments around drilling platforms.
Exploratory drilling activities around the Flower Gardens Banks,
a coral reef system in the Gulf of Mexico off the North Texas coast, have
been the subject of several monitoring studies. To protect these unique
coral reefs, several stipluations were made in permits, including that
drill mud and cuttings be disposed of by shunting through a downpipe that
terminates approximately 10 meters above the bottom for all drilling within
three miles of the banks, and that no drilling be allowed within one mile
of the banks (Gettleson, 1978). During and after drilling of an exploratory
well near the East Flower Garden Bank, there was a significant increase
compared to pre-drilling values in concentration of barium, iron and lead in
sediments at the drill site (Continental Shelf Associates, 1975). Barium
concentration increased from 22 to 425 mg per kg (ppm); iron concentration
increased from 8.3 to 13,000 ppm; and lead concentration increased from 4.6
to 12.7 ppm. There was no change in sediment hydrocarbon concentration due
to drilling. Because, the drilling mud/cuttings outfall was located near
the bottom, elevated metals concentrations in sediments were restricted to
a small area near the discharge site.
In an investigation around another exploratory well nearby, mean
barium concentrations in sediments decreased with distance from the discharge
pipe after drilling (Continental Shelf Associates, 1976; Gettleson, 1978).
Mean sediment barium concentration at the drill site before drilling was
560 ppm. After drilling, sediment mean barium concentrations were 2,924,
1,953, 1,750 and 989 ppm for circles around the drill site with radii of
100, 300, 500, and 1,000 meters. No excess barium was detected in the
coral reef zone after drilling (barium concentrations 12.4 - 16.8 ppm).
Based on these results, Gettleson (1978) estimated that approximately 50
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55
percent of the drilling mud barium discharged was deposited within 1,200
meters of the discharge point.
In reviewing results of investigations of distribution of drilling
mud-derived barium around five exploratory drill sites in the Gulf of Mexico,
Gettleson and Laird (1980) concluded that the distance from the rig to which
barium is dispersed and its concentration in bottom sediments depends on
types and quantities of mud discharged, hydrographic conditions at the time
of discharge and height above the bottom at which discharges are made. There
were large differences in the distribution of barium in sediments around and
down-current from the five wells after drilling was completed (Figure 11).
Some trends do emerge however. In the examples included in Figure 11, sedi-
ment barium concentration was higher 100 meters down-current from the dis-
charge than immediately under the discharge pipe, indicating that even when
muds are shunted to near the bottom, some down-current drift takes place.
Bottom currents in the vicinity of these wells were generally less than 8
cm/sec. In all cases sediment barium concentrations were approaching back-
ground within 1,000 meters of the discharge. There was a tendency for some
of the barium in drilling mud discharged at or near the surface (Figure 11,
Block 367) to be transported further down-current before deposition than
barium in drilling mud discharged near the bottom. This was not consistent,
however.
Barium was used as a drilling mud tracer because of its extremely
high concentrations in the muds being discharged (the muds were 87 - 90
percent barite by weight) (Gettleson and Laird, 1980). Other metals associ-
ated with drilling, muds showed much lesser enrichment in sediments when any
enrichment at all could be demonstrated. For instance, in another study of
drilling mud dispersion from an exploratory rig in the northwest Gulf of
Mexico, Trocine et al. (1981) reported elevated post-drilling levels of
sediment barium as high as 5,200 ppm in the upper one centi'meter of sedi-
ment at stations nearest the rig. Sediment barium concentration dropped to
background level at the 5 cm depth in the sediment. Surficial sediments 1.9
km down-current from the discharge contained a three-fold above background
barium concentration. These data show that metal enrichment of sediments
from discharged drilling mud is restricted to the surficial layer of sediment.
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900
TOO-
1861
LEGEND
= WELLS No. 3 a 4, BLOCK A-389, TRANSECT
= WELL No.l, BLOCK A-367, TRANSECT II
= WELL No.l, BLOCK, A-502, TRANSECT TITT
= WELL No.l, BLOCK, A-85, TRANSECT IZ
-50J
0 100 300 500 1000 2000
DISTANCE FROM DRILLSITE (METERS)
3000
Figure 11. Relative concentration of barium in bottom sediments at different
distances from four drilling rigs, in the northwestern Gulf of Mexico
(From Gettleson and Laird, 1980).
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57
Enrichment of iron in the sediments was found only at stations closest to
the rig. Chromium concentrations did not deviate significantly from normal
at any station.
Following an exploratory drilling operation on the Atlantic outer
continental shelf off Jacksonville, Florida during which 23,863 barrels
(1,002,246 gal.) of drilling mud and 1,508 barrels (63,336 gal.) of cuttings
were discharged, no increase in concentration of barium or chromium could
be detected at any station around the rig (EG&G, 1980). Sediment traps
collected particulates containing elevated levels of barium and chromium.
The authors concluding that most of the discharged drilling muds must have
been carried by bottom currents out of the study area.
Slightly different results were obtained around an exploratory
platform on the Tanner Bank off Los Angeles, California. During the 85-
day study period, 2,854 barrels (119,868 gal.) of mud and cuttings contain-
ing 863,290 kg of solids were discharged. Current speeds in the area averaged
21 cm/sec (Ecomar, 1978; Meek and Ray, 1980). Based on sediment trap data,
the authors estimated that 12 percent of the total solids discharged settled
out in the area between the 50 and 150 meter radii from the platform. A
majority of the remainder of the discharged solids settled initially within
a 50 meter radius of the platform. However little or no visible accumula-
tion of drilling mud and cuttings was observed in this area, so most of the
material (estimated between 44 and 94 percent) was transported out of the
area by strong bottom currents.
There were slight increases in post-drilling compared to pre-
drilling sediment samples in concentrations of barium, chromium-and lead.
Pre-drilling levels of barium ranged from 87 to 156 ppm and rose to 124 to
1,680 ppm in post-drilling samples. Sediment chromium concentrations
rose from less than 0.7 ppm before drilling to 0.5 to 6.11 ppm after drill-
ing. The range of sediment lead concentrations before drilling was 0.2 to
1.8 ppm and rose in post-drilling samples to 0.25 to 9.90 ppm.
Mariani et al. (1980) studied changes due to drilling mud and
cuttings discharge in physical and chemical properties of sediments around
the site of an exploratory drilling operation on the Atlantic outer continental
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58
shelf off New Jersey. Drilling discharges caused some localized changes in
sediment grain size distribution and clay minerology. There was a slight
decrease in percent gravel and sand and slight increase in percent silt
and clay in post-drilling compared to pre-drilling sediment samples. In-
terestingly, percent montmorillonite clay in the sediment decreased from
14.45 - 26.90 percent in pre-drilling sediment samples to 10.2 - 18.1 per-
cent in post-drilling samples. Percent illite, chlorite and kaolinite
increased in post-drilling samples compared to pre-drilling samples.
Because the mud used in this operation contained 24 - 38 percent mont-
morillonite by weight and much smaller amounts of the other clay types,
while cuttings contained significant amounts of illite and kaolinite
(Ayers et al., 1980a), it is likely that the change in clay minerology .
in sediments was due primarily to accumulation of drill cuttings. These
changes in the clay fraction of the sediments extended out approximately
800 meters from the rig.
Sediment samples collected before and after drilling were analyzed
using a weak acid Teachable atomic absorption spectrometry method for several
metals (arsenic, barium, cadmium, chromium, copper, mercury, nickel, lead,
vanadium, and zinc). Concentrations in sediments of only lead, barium,
nickel, vanadium and zinc were higher in the post-drilling than in the pre-
dilling survey. Increases in lead and zinc concentrations were small and
were within the normal concentration range for these metals in sediments
from the general area. Nickel and vanadium were not present in the mud
and cuttings insignificant concentrations, and so probably came from another
source. Increases in sediment barium concentration were small. However,
the weak acid extraction method (designed to extract potentially bioavailable
metals) is a poor method for solubilizing barium and other metals from barite.
Subsequent analyses by Mariani (personal communication) of archived pre- and
post-drilling sediment samples for total barium by neutron activation analysis
revealed significant differences between pre- and post-drilling sediment
total barium concentrations. Sediment total barium concentrations before
drilling started ranged from 147.0 to 276.28 ppm. In post-drilling sediment
samples, total barium concentration ranged from 192.39 to 3,477.18 ppm. The
highest concentration was from a sediment sample collected approximately 100
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59
meters south west of the drill site. Sediments at the drill site contained
159.33 ppm total barium before drilling and 1075.38 ppm after drilling.
Post-drilling sediment samples west and south south-west of the drill site
contained 192.4 and 294.7 ppm barium, respectively, close to the normal
range for pre-drilling sediment samples.
Crippen et al (1980) studied distribution and concentration of
mercury, lead, zinc, cadmium, arsenic, and chromium in surficial sediments
around the Netserk F-40 well in the Beaufort Sea.. During drilling of this
well, approximately 7,300 barrels (306,600 gal.) of mud and cuttings were
discharged to the ocean. The barite used to formulate these muds contained
high concentrations of mercury, lead, zinc, cadmium, and arsenic (Table 7 ).
All these metals were present in one or more sediment samples in the vicinity
of the discharge site, especially within 45 meters of the discharge, at con-
centrations significantly higher than background. The mean background con-
centration of mercury in sediments from the region was 0.07 ppm. Mercury
concentrations as high as 6.4 ppm were detected within 45 meters to the
south west of the discharge site (Figure 12). Between 90 and 220 meters
to the south west and west of the discharge site, sediment mercury con-
centrations ranged from 0.16 to 1.0 ppm. Elevated mercury concentrations
were also observed in a transect to the north east on the opposite side
of the artifical island from the discharge to a distance of about 1,800
meters. Distribution in sediments around the discharge site of cadmium,
chromium, lead and zinc was similar to that of mercury. Highest concentra-
tions of these metals were recorded at the station closest to the discharge,
where the sediment sample contained visibly identifiable drilling mud. Con-
centrations in this sample of arsenic, cadmium, chromium, lead,'and zinc
were 23.0, 5.9, 70.0, 467, and 1,360 ppm, respectively, all above back-
ground values.
Sediments in the vicinity of the Buccaneer oil and gas field,
drilled in the early 1960's off Galveston, Texas, contain elevated levels
of barium, cadmium, and strontium (Wheeler et al., 1980). Mean barium
concentration in sediments near platforms was 403 ppm compared to 151 ppm
in nearby control areas. Elevated barium and strontium could have come
from brines discharged from the production platforms. The brines are
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60
Distribution of Mercury
in the surficial Netserk sediments
(From Crippen et al., 1980).
285'
270'
255ฐ
235'
335'
25ฐ
215'
150ฐ
'T.~3 zone of surficial sand and gravel due to Netserk construction and erosion
F7771 -ogtoO.iejLjgg'1
^^ 75 to 1jug g"1
Figure 112.
.60ฐ
>6 jug g
Dry weight background Hgconcentration- -068JJg g"
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61
enriched in these alkali metals compared to seawater. Much of the barium
and some of the strontium also (a normal contaminant of barites) were pro-
bably derived from drilling muds discharged 10 to 15 years earlier during
drilling of the field. Cadmium probably came from corrosion'Of rig struc-
tures. Elevation of mean sediment cadmium concentration was not large
(1.1 ppm versus 0.8 ppm for control). All other metals analyzed (cobalt,
chromium, copper, iron, manganese, nickel, lead and zinc) had similar con-
centrations in the oil field sediments and in sediments from control areas.
Tillery and Thomas (1980) measured metal concentrations in sedi-
ments around several long-established production platforms in the Gulf of
Mexico off Louisiana. Aluminum, calcium, cadmium, chromium, copper, iron,
nickel, lead, vanadium, and zinc were analyzed in sediment samples collected
100, 500, 1,000, and 2,000 meters down-current from four production plat-
forms and compared to values for control sediment samples. Gradients were
observed of decreasing concentration in surficial sediments with distance
from some platforms of barium, cadmium, chromium, copper, lead, and zinc.
Concentration ranges in the gradients were not large and concentrations of
these metals in sediments 100 meters from .production platforms were only
slightly higher than control values. These sediment metal gradients were
attributed by the authors to discharged drilling fluids and cuttings,
discharged produced waters, metallic debris on the bottom, pipelines,
platform-related activities, or recreational boating.
All these investigations demonstrate that metals associated with
drilling muds, especially barium, tend to accumulate in surficial bottom
sediments near the rig when drilling fluids and cuttings are discharged to
the ocean. Barium, becuase of its high concentration in most drilling muds,
its extreme insolubility as barite.and its high density, is the drilling
mud metal enriched to the greatest extend in sediments down-current from a
drilling mud discharge. Distribution of mud-associated metals in sediments
is extremely uneven, but generally there is a definite gradient of decreas-
ing concentration with distance from the discharge. The greatest enrich-
ment in sediment metal may be directly under the mud discharge or a short
distance down-current depending on current speed and water depth. Major
enrichment of sediment metal concentration usually occurs within a distance
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62
of about TOO meters or less from the discharge point. Background concen-
trations are usually reached within 1,000 meters down-current from the
discharge. Shunting of drilling muds to near the bottom seems to have
only a minor effect on metal concentration in nearby sediments. Concen-
trations of metals are higher in sediments near the outfall and the
gradient of decreasing concentration with distance from the platform is
steeper than when muds are discharged at or near the bottom.
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63
TOXICITY OF DRILLING FLUID COMPONENTS
A common practice in evaluating the toxicity of a complex mixture
like drilling mud is to determine the toxicity of individual pure components
or ingredients of the mixture. The primary purpose of such bioassays is to
identify the ingredient or ingredients that cause or contribute most to the
toxicity of the complete mixture. The assumption is made that toxicities of
individual ingredients are approximately addative and that physical and/or
chemical interactions among ingredients do not take place during formulation
or usage of the mixture which might affect the toxicity of the mixture. These
assumptions probably are not valid for used treated drilling fluids. Sprague
and Logan (1979) showed that the sum of. toxicity of individual ingredients of
a used drilling fluid was a poor p.redicter of the acute toxicity of the whole
used mud to freshwater fish. A few of the chemical and physical reactions that
take place in drilling fluids during usage have been discussed above. Neverthe-
less, recognizing these limitations, bioassays with drilling mud ingredients
are useful for identifying the most toxic ingredients of different types of
muds. If particularly toxic or otherwise harmful ingredients are identified,
they can in some cases be replaced by less dangerous substitutes, or muds contain-
ing such ingredients can be prohibited for ocean disposal.
Acute Toxicity
A rather large volume of literature exists on the acute toxicity
to freshwater animals, particularly trout, of drilling mud ingredients (Logan
et al., 1973; Land, 1974; Beckett et a!., 1976; Sprague and Logan, 1979).
Bioassays in fresh water with freshwater animals cannot be extrapolated to
the marine environment, because mechanisms of drilling mud-mediated toxicity
appear to be different in marine and freshwater systems. Based on observations
of Hrudey (1979) and Sprague and Logan (1979), it appears that the main causes
of toxicity of some used drilling muds to freshwater organisms are related to
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64
the high pH and high salt concentration (particularly potassium) of the mud.
Fresh water has a low ionic concentration (by definition) and is poorly
buffered. Freshwater organisms, therefore, generally are very sensitive to
changes in pH and ionic concentration of the ambient medium. Seawater, because
of its high ionic strength, has a higher buffer capacity. Marine and especially
estuarine organisms are more tolerant than freshwater species to small changes
in ionic concentration of the medium. Therefore, KC1 muds which are quite
toxic to freshwater fish, are generally inocuous to marine species and alkaline
muds like most chrome lignosulfonate muds have little effect on seawater pH,
except at very high concentrations.
The limited data available on acute toxicity of drilling mud ingred-
ients to marine and estuarine organisms are summarized in Table 13. Of the
four major drilling mud ingredients which make up more than 90 percent of most
water-based muds (Perricone, 1980), (barite, bentonite, lignite and chrome
lignosulfonate), only chrome and ferrochrome lignosulfonate show significant
toxicity to any but the most sensitive species and life stages of marine
organisms. Plant tannins from tree bark and sodium phosphate salts are the
other major ingredients which show some toxicity to marine organisms. Other
major ingredients are very nearly inert.
Two biocides are included in Table 13. Formaldehyde is moderately
toxic and Dowlcide G (sodium pentachlorophenol) is extremely toxic. Dowi.cide B
(sodium salt of 2,4,5-trichlorophenol) is also used sometimes as a bactericide
in drilling muds (Land, 1974). Its toxicity is likely to be slightly less than
that of Dowicide G (Zitko, 1975). Chlorinated phenols are not currently
permitted in drilling fluids destined for ocean disposal. Formaldehyde, as
paraformaldehyde, is permitted. When 'used it is maintained in the drilling mud
at a concentration of about 700-1,400 ppm (Land, 1974). Thus a 100-fold dilution
of the drilling mud will bring its concentration into the sublethal range.
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65
Table 13. Acute toxicity of drilling fluid components to
estuarine and marine organisms
Compound
Bioassay Organism
96. Hr, LC50
Reference
Aquagel^ (Wyoming
bentonite)
Bentonite
Barite (barium
sulfate)
Calcite (calcium
carbonate)
Siderite (iron
carbonate)
Carbonox^ (lignitic
material)
Lignite
Chrome lignosulf-
onate
Chrome-treated
Jignosulfonate
Ferrochrome
1ignosulfonate
oyster Crassostrea virginica
shrimp Pandalus hypsinotus
copepod Acartia tonsa
alga Skeletonema costatum
oyster Crassostrea virgin-Lea
several fish and invertebrates
sail fin molly M. latipinna
oyster Crassostrea virginica
shrimp Pandalus hypsinotus
copepod Acartia tonsa
alga Skeletonema costatum
sail fin molly M. latipinna
sail fin molly M.' latipinna
several fish and invertebrates
sail fin molly M. latipinna
>7,500
100,000
22,000
9,600
110-119 (192
day LC50)*
>7,500
>100,000
50-60 (216
LC50)*
>100,000
590
385-1650
>100,000
>100,000
>7,500
>15,000
sailfin molly M. latipinna
white shrimp Penaeus setiferus
Dungeness crab Cancer magister
Dock shrimp Pandalus danae
12,200
465
210 (144
Hr LC50)
120 (144
Hr LC50)
Dougherty, 1951
Atlantic Richfield, 1978
Shell Oil Co., 1976
Shell Oil Co., 1976
Cabrera, 1971
Dougherty, 1951
Grantham and Sloan, 1975
Cabrera, 1971
Atlantic Richfield, 1978
Shell Oil Co., 1976
Shell Oil Co., 1976
Grantham and Sloan, 1975
Grantham and Sloan, 1975
Dougherty, 1951
Hollingsworth and Lockhart,
1975
Hollingsworth and Lockhart,
1975
Chesser and McKenzie, 1975
Carls and Rice, 1980
Carls and Rice, 1980
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66
Table 13. Continued
Iron lignosulfonate white shrimp Penaeus setifems
Cellulosic calcium
carbonate work-
over additive
2,100 Chesser and McKenzie, 1975
Jelflake^ (shredded
cellophane)
R
Impermex (pregel-
atinized starch)
Fibertex^ (shredded
cane fiber)
Mica
Low molecular wt.
polyacrylate
Quebracho (tannin)
Modified hemlock
bark extract
(tannin)
Tanio (tannin)
Sodium and pyro-
phosphate
Oilfos^
(Na tetrBphosphate)
Quadrafos^
(Na polyphosphate)
Oil well cement
klhite lime
Formaldehyde
(R)
Dowacide G^
(79% Na-
pentachloro-
phenol)
white shrimp Penaeus setifevus
several fish and invertebrates
several fish and invertebrates
oyster Crassostvea wivg-inica
several fish'and invertebrates
several fish and invertebrates
white shrimp Penaeus setiferus
sail fin molly M. latipinna
1,925
>7,500
500-7500
3,000
>7,500
>7,500
3,500
158
white shrimp Penaeus setiferus 265
oyster Crassostrea virginica 90-170 (108
day LC50)*
sail fin molly M. latipinna
several fish and invertebrates
several fish and invertebrates
several fish and invertebrates
several fish and invertebrates
pompano Traahinotus oarolinus
sheepshead minnow Cyprinodon
variegatus (2 wk. fry)
pinfish Lagodon rhomboides
(48 hr. prolarvae)
Chesser and McKenzie, 1975
Dougherty, 1951
Dougherty, 1951
Dougherty, 1951
Dougherty, 1951
Dougherty, 1951
Chesser and McKenzie, 1975
Hollingsworth and Lockhart,
1975
Chesser and McKenzie, 1975
Cabrera, 1971
7,100 Grantham and Sloan, 1975
>7,500 Dougherty, 1951
500-7500 Dougherty, 1951
70-450 Dougherty, 1951
70-450 Dougherty, 1951
25-31 Birdsong and Avault, 1971
0.52 Borthwick and Schimmel,
1978
0.066 Borthwick and Schimmel,
1978
*, concentrations are given as ppm turbidity which is usually
much lower than ppm material added.
M. = Mollieniasis
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67
Formaldehyde is highly volatile and reactive with organic molecules and is
readily biodegraded by bacteria when present at low concentration. Thus, it
is unlikely to be persistent in the marine environment.
Drilling muds may contain chromium in a variety of chemical forms.
Most is tightly bound to 1 ignosulfonate. Virtually all the chromium in a
drilling mud that has been used for extended periods will be in the trivalent
state, even though it may have been added as inorganic hexavalent chromium
salt. Acute toxicity to marine animals of several inorganic trivalent and
hexavalent chromium salts is summarized in Table 14. Trivalent chromium salts,
primarily because of their extremely low solubilities in seawater, have low
toxicities. It is interesting to note, however, that the marine polychaete
Myxicola infundibulwn can detect and respond behaviorally to as little as
1 X 10"4 (5.2 ppm) trivalent chromium (Ward, 1977). Most species of marine
animals are much more sensitive to hexavalent chromium salts than to trivalent
salts, though there is a great deal of interspecies variation in sensitivity
to the former. Sensitivity of blue crabs Callinectes sapidus to Cr is
inversely related to ambient seawater salinity, probably reflecting a change
in the chemical form of Cr with change in ionic concentration of the
medium (Frank and Robertson, 1979). In polychaete worms Neanthes arenaceo-
dentata, there is complete inhibition of reproduction at 1.0 ppm and significant
reproductive suppression at concentrations as low as 12.5 ppb Cr as potassium
dichromate (Oshida et al., 1981). By way of comparison, hixavalent chromium
appears to be slightly more toxic than trivalent chromium in mammals (Tandon
et al., 1978). In fresh water, particularly soft water, trivalent chromium
is much more toxic to most species than hexavalent chromium (Land, 1974).
In used chrome 1ignosulfonate drilling mud, the proportion of total
or dissolved chromium which is present in an ionized inorganic form is not
known (Liss et al., 1980). As discussed earlier, most of the chromium is
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68
Table 14. Acute toxicity of inorganic trivalent
chromium salts to marine animals
\
Compound
Trivalent Cr
CrCl3-
Cr(N03)
Hexavalent Cr
K2Cr207
K2Cr207
K2Cr207
K2Cr 04
Na2Cr 04
Cr03
Species Exposure Time
polychaete Neanthes arenaceo-
dentata
yellow eye mullet Aldrichetta
forsteri
polychaete Neanthes arenaoeo-
dentata
blue crab Callinectes sapidus
bleak Alburnus alburnus
(fish)
harpacticoid copepod Nitoara
spinipes
polychaete Nereis virens
crab Pagurus longicarpus
clam My a arenaria
starfish Asterias forbesi
snail Nassarius obsoletus
killifish Fundulus heteroolitus
yellow-eye mullet Aldrichetta
forstevi
small -mouthed hardyhead
Atherinosoma micros toma
polychaete Neanthes arenaceo-
dentata
polychaete Capitella oapitata
293 days
96 hr
96 hr 2
168 hr 1
96 hr
(1 o/oo salin-
ity)
(15 o/oo salin-
ity)
(35 o/oo salin-
ity)
96 hr
168 hr
96 hr 24
168 hr 31
28 day 0.
96 hr
28 day
and hexavalent
LC50
(ppm)
50.4
53
.22-3.63
.15-1.89
34
89
98
240
16
0.7
2.7
8.0
10.0
10.0
44.0
.0-31.2
.6-40.2
55-0.70
5.0-8.0
0.28
Reference
Oshida et al . , 1981
Negilski, 1976
Mearns et al . , 1976
Frank & Robertson,
1979
Linden et al . , 1979
Eisler & Hennekey,
1977
Negilski, 1976
Reish et al . , 1976
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69
probably associated with the lignosulfonate, clay and/or barite fractions
of the mud. Thus, the data in Table 14 give no indication of the contribution
of chromium to the toxicity of drilling muds.
Another material, used in small amounts in some drilling muds, which
could show significant toxicity to marine animals is detergent or surfactant.
Detergents are used to aid dispersion in the aqueous phase of the mud of
poorly soluble mud components such as aluminum stearate, gilsonite, etc. Poly-
ethoxylated alkyl phenols like Aklaflo-E or Aklaflo-S may be added to drilling
muds at concentrations of 1-10 Ibs/bbl (API, 1978). Structurally related poly-
oxyethylene esters and ethers have acute toxicities in the range of 1-40 ppm for .
Atlantic salmon Salmo solar and 2.5-14,000 ppm for the amphipod Gcomarus oceanicus
(Wildish, 1972). Anionic detergents of the linear alkylate sulfonate and alkyl
aryl sulfonate types also are used sometimes in drilling muds. They have acute
toxicities to freshwater and marine invertebrates and fish of 0.4 to 40 ppm
(Abel, 1974). Toxicity increases with decrease in water hardness (or salinity)
and decrease in alkyl side chain length.
Chronic and Sublethal Effects
Relatively little research has been performed to date on chronic and
sublethal effects of individual drilling mud ingredients to marine animals.
Nearly all the research has been performed with barite and various biocides, and
strangely enough nothing has been done with chrome lignosulfonate, the only
major drilling fluid ingredient exhibiting any acute toxicity to marine
animals.
Several experiments were performed on effects of barite or biocides
on recruitment from the plankton of benthic invertebrates to sandy sediments
in experimental aquaria receiving unfi-ltered natural seawater (Tagatz and
Tobia, 1978; Cantelmo et al., 1979; Tagatz et al., 1980). In barite experiments,
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70
aquaria (56 cm by 9 cm by 12 cm high) contained 6 cm clean sand, a 1:10 or 1:3
sand:barite mixture or 5.5 cm sand overlain with a 0.5 cm layer of barite. Un-
filtered natural seawater was supplied at a rate of 12 liters/hr.
After ten weeks, abundance, primarily in the upper 2 cm of meiofaunal
representatives of the Rotifera, Foraminifera, Hydrozoa, Turbellaria, Ostrocoda,
Polychaeta, and Bivalvia was unaffected by the presence of barite (Cantelmo et
al., 1979). However, abundances of nematodes, harpacticoid copepods and copepod
nauplii were higher in the 1:10 and 1:3 sand:barite mixtures than in pure sand.
Nematodes were less abundant in the aquarium containing the 5 mm barite layer
over sand than in the control aquarium containing only sand. Highest total
meiofaunal abundances were in aquaria containing the sand-barite mixtures.
Macrofauna showed a greater response than meiofauna to barite (Tagatz
and Tabia, 1978; Tagatz et al., 1980). A layer of 5 mm barite on the sand sub-
strate significantly reduced recruitment of macroinvertebrates to the aquaria
(Table 15). Particularly affected were molluscs (especially Laevocardiim mor-
toni] and annelids (especially Armandia agilis}. Sand-barite mixtures had a
much less dramatic effect. Abundances of the dominant polychaetes, Armandia
agilis and Prionospio heterobranchia, were decreased compared to controls by about
50 percent in 1:10 barite:sand. Abundance of annelids in the 1:3 barite:sand
mixture was reduced even further. Molluscs and several other taxa were actually
more abundant in the 1:10 barite:sand mixture than in the control, so that
total numbers of animals and species were slightly, but not significantly
higher, in the 1:10 mixture than in the control. A few species occurred only
in the sand-barite mixtures.
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71
Table 15. Numbers of animals and species collected from aquaria
containing sand alone or sand-barite mixtures and
receiving unfiltered natural seawater at a flow rate
of 200 ml/minute for 10 weeks (From Tagatz and Tobia,
1978; Tagatz et al., 1980).
Number of individuals or species
(in brackets)
Taxon
Mollusca
' Laevocardiwn mortoni
Anomalooardia aubev-ia.net.
Annelida
Armandia agilis
Prionospio heterobranchia
Chordata
Molgula manhattensis
Other Phyla
Total
Control
474 (21)
268
28
368 (14)
180
145
77 (1)
77
47 (8)
966 (44)
Barite 1:10
611 (17) '
364
77
233** (18)
90
85
122 (1)
122
65 (10)
1031 (46)
Barite 1:3
413 (17)
219
84
54** (11)
10
7
114 (1)
114 .
39 (8)
620* (37)
5mm Barite Cover
210** (12)**
114
41
33** (10)
0
1
I" 0)
111
49 (10)
403** (33)**
*, significantly different from control at 5% level; **, significantly different
from control at 1% level.
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72
It seems likely that much of the effect of barite on recruitment.
from the plankton of benthic invertebrates to sandy sediments was due to
barium-mediated changes in sediment texture, and not to any chemical toxicity
of barite. Barite has a much finer grain size (mean less than 60 ym) than
sand. The sand substrate in control aquaria contained no silt-clay fraction,'
whereas in aquaria containing sand-barite mixtures, the clay-silt fraction
was 5.6 to 16.3 percent (Cantelmo et al., 1979). Grain size distribution,
mineralogy, texture and organic content of sediments have a profound effect
on settlement of planktonic larvae (Thorson, 1956; 1966). A change in sediment
characteristics has the effect of rendering the sediment unsuitable for some
species, but more suitable for others.
When shrimp Palaemonetes pugio-were exposed to 500 ppm barite
(present primarily as a fine precipitate, since this is far in excess of the
solubility of BaS04 in seawater) for periods up to 106 days, they ingested the
barite (Brannon and Rao, 1979; Conklin et al., 1980). Although this did not
affect survival of the shrimp, several sublethal responses were observed. Barite
ingestion caused damage to the epithelium of the posterior midgut, possibly by
abrasion. The shrimp also incorporated grains of barite into statocysts at
the time of molting. The shrimp accumulated barium in the exoskeleton and
soft tissues. Barium concentration in the carapace of intermolt control shrimp
ranged from 67 to 108 mg/kg while barium concentration in the carapace of shrimp
exposed for up to 21 days to 500 ppm barite ranged from 202 to 662 mg/kg. Other
tissues of barite-exposed shrimp showed similar elevations in tissue barium
concentration. Barium is a normal constituent of marine invertebrate tissues
and calcified structures (Chow and Snyder, 1980). The chemical form and physio-
logical significance of elevated barium concentrations in barite-exposed animals
is unknown.
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73
Thompson and Bright (.1977) applied 25 ml of slurries of one part
barite in one part water or one part Aquagel (bentonite clay) in two parts
water to small colonies of three reef corals, Diploria strigosa, Montastrea
cavernosa and Montastrea annularis. This heavily coated the surface of the
corals. Despite this extreme treatment, the corals were able to clear their
surfaces of the sedimented material rapidly. D. strigosa cleared itself faster
than the other species. Barite and Aquacel were cleared at about the same rate
as natural calcium carbonate sand. Mean clearing rates for the three species of
CaCOo, barite and Aquagel were 257, 251 and 293 mm^/hour, respectively.
These investigations all show that pure barite is not a serious
environmental pollutant except when present for extended periods at very high
concentration. Barite in used drilling mud interacts with and is partially
.bound to the clay-lignosulfonate fraction. In this form, its behavior in the
marine environment and effect on marine organisms can be expected to be different
from that of pure barite.
Tagatz et al. (1980) also studied the effects of three biocides
Dowicide G-ST (79% sodium pentachlorophenol, 11% sodium salts of other chloro-
phenols), Surflo B-33 (37.4% isoprcpyl alcohol, 17% sodium salt of 2, 2' methyl-
enebis-4,6-dichlorophenol, 8% sodium salts of other chlorophenols) and Aldacide
(91% paraformaldehyde), on recruitment of benthic invertebrates to sandy sub-
strata in aquaria. The biocides were metered into the inflowing water at a
constant rate. Recruitment"to the sand substrate of most species was adversely
affected by the two chlorophenol biocides, Dowicide and Surflo, at concentrations
in the 10 to 205 yg/ฃ range (Table 16). "Molluscs were the only group adversely
affected by the 10-18 yg/liter concentrations. The paraformaldehyde biocide,
Aldacide,was without effect at concentrations of 14 and 273 yg/liter.
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74
Table 16. Effects of biocides on recruitment from the plankton
of benthic macrofaunal invertebrates to sand substrata
in aquaria. Biocides were metered into inflowing water
to obtain concentrations indicated. (From Tagatz et al.,
1980).
Phylum
Mollusca
Annel ida
Arthropoda
Cordata
All Phyla
Bioeide Concentration (yg/liter)
DcWicide G-ST Surflo B-33
18 183 10 205
* * * *
NS * NS *
NS * - -
NS *
* * NS *
Aldacide
14
NS
NS
-
NS
NS
273
NS
NS
-
NS
NS
*, number of individuals significantly less than control (a ? 0.05)
NS, not significantly less than control
-, insufficient numbers collected for statistical analysis.
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75
Chlorinated phenol biocides are obviously quite toxic to benthic
invertebrates. However, as stated elsewhere, they are not permitted for use
in drilling fluids destined for ocean disposal. Paraformaldehyde at concen-
trations up to 273 ppb was without significant effect. Aldacide is recommended
for use in amounts up to 300 g/bbl (about 1,500 ppm paraformaldehyde). Its
rate of loss from discharged used drilling mud by dilution, biodegradation and
evaporation would probably be sufficient to maintain its ambient concentration
well below toxic levels.
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76
TOXICITY OF USED DRILLING FLUIDS TO MARINE ANIMALS
Bioassay Protocols
A used drilling fluid, especially a treated mud from a deep hole, is
an extremely heterogeneous material. It contains water-soluble materials,
clay-sized particles of moderate density that sediment slowly in seawater,
and high-density particles that sediment rapidly. These fractions tend to
separate rapidly when the drilling fluid is added to seawater in a bioassay
aquarium or when it is dishcarged from an offshore drilling rig. This makes
it extremely difficult to design a bioassay protocol in which test organisms
are exposed uniformly and reproducibly to a drilling mud-seawater mixture of
/
known concentration and/or which will at least roughly simulate the kind of
exposure an organism might encounter in the vicinity of the drilling mud dis-
charge from an offshore rig.
The simplest approach has been to add whole drilling mud to seawater on
a volume:volume basis to establish several exposure concentrations. Test
organisms are exposed to these mixtures which are aerated, mixed or left
unmixed during the bioassay (McLeay, 1976; Houghton et al., 1980a; Tornberg
et al., 1980).
Another approach is to evaluate toxicity of different drilling fluid
fractions on drilling fluid-seawater mixtures which roughly simulate the
types of exposure organisms in different marine habitats might encounter.
These bioassay protocols are similar to those recommended for evaluation of
the environmental impact of dredged material (EPA/COE, 1977). Tables 17 and
18 summarize methods for preparation of drilling fluid bioassay media accord-
ing to protocols recommended by EPA, Region 2 and according to modified
protocols of Neff, et al. (1980, 1981), respectively. Mudrseawater
mixtures prepared by the two protocols are quite similar. The LP
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77
Table 17. Methods for preparation of drilling fluid bioassay media
according to recommendations of EPA, Region 2 (based on
EPA/COE, 1977).
A. Liquid Phase (LP). One part by volume of drilling mud is added to four
parts unfiltered seawater. The pH is adjusted, if necessary, to within
0.2 pH unit of seawater pH with acetic acid. The slurry is stirred
mechanically and aerated vigorously for 30 minutes. The mixture is
allowed to settle for one hour. The supernate is centrifuged and filtered
through a 0.45-micron filter. The liquid phase is used immediately in
bioassays. The 100% LP contains the water-soluble fraction of 250,000
ppm drilling mud in water.
B. Suspended Particulate Phase (SPP). The suspended particulate phase is
prepared in a manner similar to the liquid phase. The suspended particu-
late phase is the supernate (containing soluble and suspended particulate
mud fractions) remaining after the one-hour settling period. It is the
uncentrifuged, unfiltered liquid phase. The SPP is used immediately in
bioassays. The 100% SPP contains the water-soluble and fine particulate
fractions of 250,000 ppm drilling mud in water.
C. Solid Phase (SP). The solid phase is the settled fraction obtained in
preparation of the SPP for LP preparation above. After the SPP is decanted
the SP is added to aquaria to yield a layer of mud over natural clean
sediment. Seawater is usually added and decanted at least once to remove
soluble materials. The SP preparation is the insoluble particulate frac-
tion of drilling mud.
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78
Table 18. Methods for preparation of drilling fluid bioassay media
according to Neff et al., (1980, 1981)..
A. Mud Aqueous Fraction (MAP). One part by volume of drilling mud is added
to nine parts artificial seawater (Instant Ocean, Aquarium Systems, Inc.)
of the appropriate salinity. The mixture is stirred thoroughly and then
allowed to settle for 20 hours. The resulting supernate (100% MAP) is
diluted with artificial seawater to the appropriate concentration used
immediately. It may be filtered through a 0.45-micron filter to produce
a filtered MAP. The 100%'MAP contains the water-soluble and fine particu-
late fractions of 100,000 ppm mud in water.
B. Suspended Particulate Phase (SPP). One part by volume of drilling mud is
added to nine parts artificial seawater. The mud-water slurry is air-mixed
with filtered compressed air for thirty minutes, with manual stirring every
ten minutes. The suspension is then allowed to settle for four hours before
the supernate (100% SPP) is siphoned off for immediate use in bioassays.
The SPP resembles the MAP except that the SPP contains a higher concentra-
tion of particulates and lower concentration of volatiles.
C. Suspended Solids Phase (SSP). Known volumes of drilling mud are added to
artificial seawater and the mixture is aerated vigorously during the bioassay
to keep particulates in suspension.
D. Layered Solid Phase (LSP). A measured volume of mud is layered over clean
natural sediment in an aquarium. Natural seawater is added with minimal
resuspension of mud. After 24 hours the water may be decanted and replaced
with clean seawater to remove mud solubles. Animals are added after 24-48
hours' settling.
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79
preparation of EPA resembles the MAP and SPP preparations of Neff et al.
(1980, 1981). The major difference is the ratio of mud to water used to
prepare the stock mixtures.
Flow-through exposure systems also have been used for long-term and
sublethal effects studies (Conklin et al., 1980; Krone and Biggs, 1980;
Rubinstein et al., 1980). There is danger of fractionation of drilling
fluid in such systems, resulting particularly in buildup of heavier mud
fractions in exposure tanks. Design of such a system poses several tech-
nical problems, some of which have net yet been solved.
In the discussion that follows, primarily for comparison purposes,
btoassay results of all but solid phase tests will be expressed in terms
of ppm mud added initially.
Acute Toxicity
McLeay (1975) studied the toxicity of seven Arctic drilling fluid
wastes to seawater-acclimated salmon and four species of Arctic marine
intertidal invertebrates (Table 19). Five of the seven drilling mud samples
were toxic to seawater-acclimated coho salmon Onoorhynchus kisutch at concen-
trations of less than 5 percent v/v (50,000 ppm). The most toxic drilling
mud to salmon had a 96-hr LC50 of 15,000 ppm. With a few exceptions, the
four marine invertebrates were more tolerant than salmon to the seven used .
drilling muds. Acute toxicity, measured as 96-hr. LC50, ranged from 10,000
ppm to greater than 560,000 ppm. No species was consistently more sensitive
than the others. The most toxic drilling muds were KC1 polymer mud, KC1-XC
polymer mud and weighted Shell polymer mud. The weighted gel XC-polymer mud
had a consistently very low toxicity for all species tested.
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Table 19. Acute toxicity (measured as concentration killing 50-percent of test organisms in 96 hours,
(96-hr. LC50) of seven used Arctic drilling fluids to Arctic marine fish and invertebrates.
Whole drilling muds were used. Values are in mg/x, (ppm) mud added initially (From McLeay,
1975).
Drilling Mud
Shell Kipnik, KC1 polymer
Aquitaine et al. Polar bear, seawater
polymer
Sun Bux et al Pelly, KC1-XC
polymer
Shell Niglintgak, weighted
Shell polymer
Sun Bux et al Pelly, gel
chemical -XC
Sun Bux et al Relly, weighted
gel XC-polymer
Dome Imp Imnak, gel XC-polymer
Coho salmon
Oncorhynchus
kisutch
29,000
130,000
23,000
15,000
39,000
190,000
30,000
Marine Worm
Nereis
vexillosa
37,000
220,000
41 ,000
23,000
>560,000
320,000
200,000
Softshell Clam
Mya
arenccria
42,000
320,000
56,000
10,000
>560,000
>560,000
>560,000
Purple Beach Crab
Hemigrapsus . .
nudus
53,000
530,000
78,000
62,000
>560,000
560,000
>560,000
Sand Flea
Orchestia
traskiana
-
230,000
14,000
80,000
:80,000
420,000 ฐ
:.>560,000
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81
Toxicity of four used offshore drilling muds to marine animals
was studied in some detail by Gerber et al. (1980) and Neff et al. (1980,
1981). These muds were obtained from offshore drilling sites in the Gulf
of Mexico. Composition of the drilling muds is summarized in Table 20.
The used seawater chrome lignosulfonate mud (CLS) was extensively
studied by Neff et al. (1981). Table 21 summarizes results of bioassays
with ten species of marine invertebrates and the mud aqueous fraction of
CLS mud. Acute toxicity of the static MAP, measured as 96-hr. LC50, ranged
from 32% to greater than 100% of the MAP. Since the MAP represents the
soluble and fine particulate fractions of one part mud in nine parts seawater,
these concentrations correspond to 32,000 to greater than 100,000 ppm mud added.
When the MAP was filtered through a 0.45 ym filter (FMAF), it lost little of
its toxicity, indicating that a majority of the toxicity of the MAP resided
in the soluble portion. If the MAP was changed daily during the 96-hr bioassay,
its toxicity was much higher than that of the static MAP, indicating that some
of the toxic components of the MAP were lost from the bioassay containers
under static conditions, probably by volatilization. Analysis of the bioassay
mixtures revealed that, whereas the concentration of chromium in the MAP did not
change significantly with time, the concentration of hexane-extractable, UV-
absorbing "aromatic hydrocarbons" decreased rapidly in the static MAP. This
apparently volatile material, which may include petroleum aromatics and UV-
absorbing byproducts and degradation products of lignosulfonate and lignite,
appears to contribute significantly to the acute toxicity of the MAP. Gerber,
et al. (1980) reported high concentrations of petroleum hydrocarbons in this
mud.
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82
Table 20. Composition of used drilling muds evaluated by
Gerber et al., (1980) and Neff et al. (1980, 1981)
Seawater Chrome Lignosulfonate Mud (CIS):
Major components: seawater, bentonite clay, chrome lignosulfonate, lignite,
caustic soda (NaOH), and barite (BaSCL).
Mid-Weight Lignosulfonate Mud (MV.'L):
Major components: freshwater, bentonite clay, chrome lignosulfonate, lignite
caustic soda, lirr.e (Ca(OH)?), and barite.
Minor components: defoamer, oxygen scavenger, walnut lost circulation material,
and gilsonite (a natural bituminous material).
High Weight Lignosulfoante Mud (HWL):
Major components: freshwater, bentonite clay, chrome lignosulfonate, lignite
caustic soda, soda ash (Na^CCL), sodium bicarbonate, polyanionic cellulose
derivative, and barite.
Minor components: defoamer, lubricant, and mica lost circulation material.
Spud Mud (Spud):
Major components: freshwater, bentonite clay and caustic soda..
Minor components: barite.
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83
Table 21. Acute toxicity of the mud aqueous fraction (MAP) of a used chrome
lignosulfonate drilling mud to several species and life stages of
marine animals. All 96-hour LC50 data are expressed as ppm mud
added (Data from Neff et al., 1981).
Species
Life Stage Type of Exposure1 96-Hr. LC50
Marine worm
Neanthes arenaceodentata
Marine worm
Op'fapyotroc'ha. IdbTonica
Marine worm
Di-nophilus sp.
Opossum shrimp
Mysidopsis almyra
Grass shrimp
Palaemonetes pugio
Pink shrimp
Penaeus
Coquina clam
Donax variabilis
Hard-shell clam
Meroenaria campechiensis
Marsh clam
Rangia cuneata
Juveniles
Adults
Adults
Adults
1 day old
3 day old
7 day old
14 day old
4 day old
Post-larvae
Adults
Post-larvae
Juveniles
Adults
Adults
Adults
Static MAP.
Static FMAF
Static MAP
MAP changed daily
Static MAP
Static FMAF
Static MAP
Static FMAF
MAP changed daily
Static MAP
Static MAP
Static MAP
Static MAP
Static MAP
Static MAP
Static MAP
Static MAP
Static MAP
Static MAP
Static MAF
Static MAF
96,000
>100,000
51,000
10,000
>100,000
>100,000
32,000
45,000
27,000
40,000
79,000
73,000
96,000
34,000
67,000
90,000
86,000
>100,000
86,000
>100,000
>100,000
1. Static MAF, the MAF was not changed during the 96-hour bioassay; Static FMAF,
the MAF was filtered through a 0.45 y filter and aerated before use in the
bioassay; MAF changed daily, MAF was replaced every 24 hours with freshly
prepared exposure medium.
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84
Tolerance of mysid shrimp and grass shrimp to the MAP increased with
age of the animals. However, adults of the marine worm Neanthes arenaaeo-
dentata were more sensitive than juveniles of the same species.
The suspended solids phase (SSP) preparation of used CIS mud was toxic
to young pink and brown shrimp Penaeus duoponm and P. azteous at a concentra-
tion of 10 ml/liter (equivalent to 10,000 ppm) (Table 22). The suspended
solids phase preparation was somewhat more toxic to young penaeid shrimp than
the mud aqueous fraction, indicating that the settleable particles, present
in the SSP and not in the MAP, contribute to the toxicity of the drilling mud
to sensitive species, perhaps by clogging the gills and interfering with
respiration. The three other species examined, an oceanic crab and two bivalve
molluscs, were unaffected by exposure to 20 ml/I (20,000 ppm) SSP preparation.
Five species of marine invertebrates varied substantially in their
sensitivity to the layered solids phase (LSP) preparation of the used chrome
lignosulfonate drilling mud (Table 23). Adult marine worms Neanthes arenace-
odentata and adult coquina clams Donax variabilis seemed to be quite sensitive
to this mud preparation, whereas the other species and life stages tested were
more tolerant. The concentrations used in this bioassay produced a layer of
drilling, mud 5 to 20 mm thick on the sand substrate of the exposure tank.
Mud aqueous fractions of the four used drilling muds varied in their
.toxicity to several species of marine animals from the Gulf of Mexico (Neff,
1980; Neff et al., 1980). The mud aqueous fraction of the used spud mud was
not acutely toxic to the three species tested (Table 24). The 100% MAP failed
to produce any mortality in 96 hours. In most cases, the MAP of the mid-weight
lignosulfonate drilling mud was more toxic than the MAP of the seawater chrome
lignosulfonate mud and the high weight lignosulfonate mud. The 96-hr LC50 of
the MAP -of the three used chrome lignosulfonate muds ranged from 12.8% MAP
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85
Table 22. Results of bioassays with five species of marine inverte-
brates exposed to the suspended solids phase (SSP) of a
used chrome lignosulfonate drilling mud. Exposure concen-
trations are in mg mud/liter of seawater (ppm). n = number
of animals per 'treatment (From Neff et al., 1981).
Life stage
Exposure
concentration
(
Salinity
(o/oo)
n
Exposure
period
(hrs.)
Percent
survival
Penaeus
duorarum
Postlarvae
10,000
28
25
168
71
Penaeus
aztecus
Juveniles
10,000
28
10
168
40
Species
Portunus Mercenariq Rangia
spinicarpus campechiensis cuneata
Adults
20,000
35
6
168
100
Adults
20,000
20
5
96
100
'Adults
20,000
20
25
96
100
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Table 23. Results of bioassays with five species of marine invertebrates exposed to the layered solid phase
(LSP) of a used chrome lignosulfonated drilling mud. Exposure concentrations are in ml mpd/liter
seawater. n = number of animals per treatment (From Neff et al., 1981).
Life stage
Exposure
concentration
(ml/1)
Salinity
(o/oo)
n
Exposure
period
(hrs)
Percent
survival
Neanthos
arenaceodentata
Ophryotrocha
labroni ca
Juveniles Adults
40 40
32 32
40 25
96 96
77.5 25
Adults
50
34
20
96
95
SPECIES
Mysidopsis
aliu'/ra
1 day
25
20
100
160
55
Donox variabilis
tcxasi ana
Juveniles Adults
(<1 cm) (>2 cm)
100 100
35 35
25 25
9G 96
32 0
Aoqjipecten
an:pl icostatus
Adults
20
20
10
96
40
. 00
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87
Table 24. Acute toxicity of the mud aqueous fraction (MAP) of four
used drilling muds to several species of marine animals.
All 96-hour LC50 values are expressed as ppm mud added.
Exposure media were changed daily during bioassays (From
Neff, 1980).
Species
Hermit Crab
Clibanarius vitattus
Brown shrimp
Penaeus aztecus
Blue crab
Callineates sapidus
Grass shrimp
Palaemonetes pugio
Opossum shrimp
Mysidopsis almyra
Life Stage
Adults
Juveniles
Adul ts
1st Zoeae
Adults
1 day old
7 day old
CIS
28,700
41 ,500
_
7,500
92,400
27,000
Mud
.MWL
34,500
16,000
-
35,000
91,000
12,800
13,000
Types1
HWL
65,600
_
>100,000
<18,000
>100,000
<16,000
32,500
Spud
_2
_
_
>100,000
>100,000
>100,000
>100,000
Marine worm
Ophpyotrocha labron-ica
Killifish
Fundulus heteroclitus
Gulf killifish
Fundulus similis
Adults 100,000
43 day fry
Adults
60,000 >100,000 >100,000
80,000
>100,000
1, CIS, seawater chrome lignosulfonate mud; MWL, midweight lignosulfonate mud;
HWL, high weight lignosulfonate mud; Sup, spud mud.
2, no bioassay performed.
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88
(12,800 ppm mud added) for first day postlarvae of opossum shrimp to greater
than 100% MAP (>100,000 ppm) for adult grass shrimp Palaemonetes pugio, marine
wormsOphryotrooha labronica, blue crabs Callinectes sapidus, and Gulf killifish
Fundulus similis.
Mud aqueous fractions of these muds plus a low density lignosulfonate mud
from the Baltimore Canyon were somewhat less toxic to marine animals from the
coast of Maine (Gerber et al., 1980, 1981) than to species from the Gulf of
Mexico. Most species were unaffected by the 100% MAP of any of the five drill-
ing muds (Table 25 and 26). Among the crustaceans, stage 1 and III larvae of
shrimp Pandalus borealis and stage V larvae of lobsters Homarus amevioanus were
sensitive to the MAP preparations to which they were exposed. The copepod
Eurytemora herdmani was moderately sensitive to the MAP of midweight and low
weight drilling muds but not to the MAP of spud mud.
The toxicity of the suspended particulate phase (SPP) preparation of the
drilling muds was also evaluated (Table 27; Neff et al., 1980). The acute tox-
icity of the SPP of the lignosulfonate muds ranged from 11.7-74% SPP (11,700- .
74,000 ppm mud added). The spud mud SPP was not acutely toxic. Adult coquina
clams Donax variabilis were more sensitive than juvenile Pacific oysters Crasso-
strea gigas to the lignosulfonate muds. Different stage larvae of Palaemonetes
pugio were equally sensitive to the SPP preparation of the HWL mud. Much of
the toxicity of these muds appears to reside in the water-soluble fraction of
the mud, as indicated by the observation that 96-hr. LC50s for the MAP and SPP
of high weight lignosulfonate mud were similar for the grass shrimp Palaemonetes
pugio.
Male amphipods Gammarus locusta, lobsters Homarus americanus, and ocean
scallops Placopecten magellanicus- were sensitive to a substrate composed of
a mixture of drilling mud and natural marine sediment (Tables 26 & 28; Gerber
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89
Table 25. Acute, toxicity, expressed as 96-hour LC50, of the mud
aqueous fraction (MAF) of five used offshore drilling
muds to cold-water species of marine animals from Maine.
All values are in ppm mud added (Data from Gerber et al.,
1980).
Mud Type
Species HWL MWL LWL CSL Spud
Crustaceans:
Crangon septemspinosa >100,000 >100,000 98,000 >100,000 >100,000
Gammarus locusta >100,000 >100,000 - -. >100,000
Pandalus borealis (Stage 1) 65,000 17,000 -
Carainus maenas >100,000 >100,000 >100,000
Homarus amerioanus (Stage V) - 5,000
Homarus americanus (Adult) - >100,000 >100,000
Bivalve Molluscs:
Mytilus edulis >100,000 >100,000 - >100,000 >100,000
Macoma balthica >100,000 - >100,000
Gastropod Molluscs:
Littorina littorea >100,000 >100,000 >100,000
Thais lapillis - >100,000
Polychaete Worms:
Nereis virens >100,000 >100,000 >100,000 >100,000 >100,000
Echinoderms
Strongylocentrotus - >100,000 >100,000
droebachiensis
Fish:
Fundulus heteroclitus - >100,000 >100,000 - >100,000'>100,000
1. HWL, high weight lignosulfonate mud; MWL, midweight lignosulfonate mud;
LWL, low weight lignosulfonate mud; CLS, seawater chrome lignosulfonate
mud; Spud, spud mud.
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Table 26. Results of the bioassays on marine organisms exposed to various fractions of used medium and light
weight lignosulfonate drilling mud and a spud mud. Unless specified all animals are adults. MAP =
mud aqueous fraction, WM = whole mud substrate, WMW = washed whole mud substrate, SSP = suspended
solid phase, N = number of animals per treatment. LC50 values are given as the ppm of MAP, WM,
or SSP. (From Gerber et al., 1981).
LC 50 values
Species
Medium Density Drilling Mud
Homarus americanus
Panadalus borealis
(Stage III)
Cancer borealis
Eurytemora herdmani
Eurytemora herdmani
Placopecten
magellanicus
Placopecten
magellanicus
Light Density Drilling Mud
Eurytemora herdmani
Eurytemora herdmani
Spud Mud
Eurytemora herdmani
MAP WM
n
16
24
25
40
38
32
20
21
24
Temp.
10-12ฐC
4ฐC
5ฐC
4ฐC
16-17ฐC
10ฐC
4.5ฐC
4ฐC
16-17ฐC
96 hrs.
>1 00000
13000
>1 00000
82000
59000
>1 00000
>1 00000
83000
67000
168 hrs. 96 hrs. 168 hrs.
84000 290000 180000
960000
60000
50000
92000 5000
> 100000 7000 3000
77000
56000
WMW SSP
96 hrs. 168 hrs. 96 hrs.
850000 780000
40000
380000
620000
320000
20000 60000
30000 10000
800000
580000
163 hrs.
380000
200000
50000
650000
580000
21
4ฐC
1 00000
1 00000
980000 940000
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91
Table 27. Toxicity of the suspended particulate phase (SPP)
preparation of four used offshore drilling muds to
adult coquina clams Donax variabilis texasiana, two
size classes of spat of the Pacific oyster Crasso-
strea gigas, and il>-=, 5- and 1-0-day-old zoeae of the
grass shrimp Palaemonetes- pugio. Ninety-six-hour
LC50 values are in ppm SPP preparation added (Data
from Neff, et al., 1980).
Species
Donax variabilis
Crassostrea gigas
Crassostvea gigas
. CLS
(Adults) 53,700
(3-10 mm)
(10-25 mm)
Palaemonetes pugio (1 day old)
(5 day old)'
(10 day old)
Mud Type
MWL HWL
29,000 56,000
53,000 74,000
50,000 . 73,000
11,800
13,200
11,700
Spud
im2
im
im
-
-
-
1. CLS, chrome lignosulfonate mud; MWL, mid-weight lignosulfonate mud; HWL,
highweight lignosulfonate mud; spud mud.
2. im, insufficient mortality to compute LC50 value.
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92
Table 28. Acute toxicity, expressed as 96-hour LC50, of the layered
solids phase preparation of four used offshore drilling muds
to cold-water species of marine animals from Maine. These
were flow-through bioassays with flow rates of 10-20 liters
per hour. Values are expressed as percent of whole mud in
natural marine substrate (From Gerber et al., 1980).
Species
Mud Type
HWL MWL LWL
Spud
Crustaceans
Crangon septemspinosa 92 82 71
Garnnazus locusta (males) 28 74
Ganrnarus locusta. (females) 88 . 90
Caroinus maenas .>100 68 89
Homarus americanus (adult) - 29 19-25
Bivalve Molluscs:
Maooma balthioa >100 ~2 >100
Plaaopecten magellanious ~ <3.2 49
Gastropod Molluscs:
Littorina littorea >100 >100
Thais lapillis ~ ~ 83
Polychaete Worms:
Nereis virens 100 >100 >100
Echinoderms:
Stvongylocentrotus (froebachiensis ~ >100 55
>100
>100
1. HWL, high weight lignosulfonate mud; MWL, midweight lignosulfonate mud;
LWL, low weight lignosulfonate mud; spud, spud mud.
2. This value is in ml of mud/liter of seawater and represents a-l-mm thick
layer spread over natural mud in the aquarium.
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93
et al., 1980, 1981). Even in these cases, a 20-30% drilling fluid-sediment
mixture or a 1-mm layer of pure whole mud was required to produce 50% mortality.
The most surprising observation was that several species could tolerate a 100%
drilling mud substrate for 96 hours.
Ocean scallops Placopecten magellanicus were quite tolerant to the MAP
but very sensitive to shole mud of washed whole mud in the substrate. These
results suggest that scallops are very sensitive to fine suspended particulates.
The 168-hr. LC50 for whole drilling mud in the substrate was 0.3 percent
(equivalent to 3,000 ppm mud in sediment). Scallops and larval shrimp also
were sensitive to suspended solids phase preparations, tending to support the
hypothesis of sensitivity to fine particulates.
The toxicity of the five typical used offshore drilling fluids has been
evaluated in 27 species representing five major animal phyla. The results
are consistent in showing that typical used offshore drilling muds have a
low order of acute toxicity to a wide variety of species and life stages of
marine animals. Even for the most sensitive species and life stages, 96-hr.
LC50 values were rarely lower than 10,000 ppm mud added for the most toxic
muds.
To comply with bioassay requirements stipulated in NPDES permits issued
for exploratory drilling in lease areas 40 and 49 on the Middle Atlantic outer
continental shelf, a Joint Bioassay Monitoring Program was established by the
Offshore Operators Committee. Eight used drilling muds of different types,
all typical of those to be used in OCS exploratory drilling activities, were
evaluated using mysid shrimp (Mysidopsis bahia) (liquid and particulate phase
bioassays) and hard shell clams Mercenaria mercenar-ia (solid phase bioassays).
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94
Composition of the muds is summarized in Appendix I, Tablesla-8a). Results
of bioassays by ERCO, Inc. (1980) are summarized in Table 29. Results of bio- .
assays on mud No. 1 were not available at this writing. Only two liquid-phase
preparations were acutely toxic to the shrimp (the seawater lignosulfonate mud,
#2 and lime mud, #3). Mysid shrimp are considered to be very sensitive to
high suspended particulate concentrations. This is confirmed by the observa-
tion that four of the suspended particulate phase preparations were acutely
toxic to the shrimp. The most toxic (#2) had a 96-hr. LC50 of 10,640 ppm
mud added. The other three mud preparations failed to produce 50 percent
mortality in 96 hours in this very sensitive species. None of the solid phase
preparations were toxic to the clams. The only preparation producing mortality
significantly higher than that of controls.was the solid phase of mud #2. This
may reflect more the unsuitability of Meroenaria meroenca-ia as a bioassay
organism than the low toxicity of solid phase preparations of drilling mud.
These clams can remain isolated, by closure of their shells, from an ambient
medium they deem noxious for several days.
Tornberg et al. (1980) examined the acute toxicity of four types of used
offshore drilling fluids from rigs in the Prudhoe Bay, Alaska area to marine
animals from the Beaufort Sea. Composition of the drilling fluids is summarized
in Appendix I, Table 9a. The 96-hr. LC50 values for polychaete worms (Melaenis
loveni), isopod crustaceans (Saduria entomon) and snails (Natica clausa,
Neptunea sp., and Buccinewn sp.) ranged from about 40 to more than 70 percent
(v/v) whole mud (400,000-700,000 ppm). LC50 values for mysid shrimp (Mysis sp.)
and amphipod crustaceans (Onismus sp. and Boeckosimus sp.) were 6-22 percent
and 22-38 percent v/v drilling mud (60,000-220,000 ppm and 220,000-380,000 ppm),
respectively. Four species of marine fish were also examined. The most sensi-
tive was the fourhorn sculpin (Myoxocephalus quadricornis) with 96-hr. LC50
values ranging from 4-35 percent used mud (40,000-350,000 ppm). There was a
tendency for drilling mud toxicity to increase with drill hole depth. The
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Table 29. Results of bioassays on six used drilling fluids typical of those used for exploratory drilling
in the mid-Atlantic DCS lease areas nos. 40 and 49. Mysid shrimp Mysidopsis bahia were used for
the liquid and suspended particulate phase bioassays. The hard shell clam Mercenavia mercenaria
was used for solid phase bioassays. Values for 96-hour LC50 in mysid bioassays are in ppm mud
added and in clam bioassays, results are given in percent survival at 96 hours (From ERCO, Inc.,
1980).
#2,
13,
#4,
#5,
#6,
#7,
#8,
Drilling Fluid
Type
Seawater lignosulfonate mud
Lime mud
Nondispersed mud
Seawater spud mud
Saltwater/ freshwater gel mud
Lightly treated lignosulfonate freshwater/seawater mud
Lignosulfonate freshwater mud
Liquid Phase
56,700
78,600
>200, 000(91. 7)1
>200, 000(98. 3)
>200, 000(88. 4)
>200, 000(51. 7)*
>200, 000(95)
96-Hr LC50 (PPM)
Suspended Particulate
Phase
10,640
13,200
>200, 000(86. 7)*'
>200, 000(96. 7)
44,800
>200, 000(55)*
101,200
Solid Phase
% Survival
83*
100
100
100
100
97
99
*, Significantly lower survival at highest concentration tested than among controls.
1, Percent survival at 96 hours In 100% phase (=200,000 ppm mud).
IQ
en
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96
most toxic mud tested was a CMC/Gel/Resin mud from 2,786 meters drilling depth
(Table 30). The authors concluded that sedentary species were less sensitive
than pelagic species to the used drilling fluids.
Similar results were obtained by Houghton et al. (1980a)with drilling
fluids from the Lower Cook Inlet, Alaska C.O.S.T. well. A high-density ligno-
sulfonate mud system (200,000-250,000 ppm barite, 3,200-5,700 ppm ferrochrome
lignosulfonate) was examined. Two species of fish (pink salmon fry Oncorhynohus
gofbuscha and staghorn sculpin Leptooottus amatus) and five species of marine
invertebrates (coonstripe shrimp Pandalus hypsinotus, mysid shrimp Neomysis integer,
amphipods Eogatnmarus conferwicolus3 isopods Gnorimosphaeroma origonensis, and
mussels Modiolus modiolus) were tested (Table 31). The most sensitive species
were the pink salmon (96-hr. LC50., 0.3-2.9 percent whole mud - 3,000-29,000 ppm)
and mysid shrimp (96-hr. LC50, 1-15 percent whole mud - 10,000-150,000 ppm). The
effect of stirring and/or aeration on the toxicity of the drilling muds was
inconsistent.
Carls and Rice (1980) studied the toxicity of six new and used offshore
drilling muds from Alaska to six species of Stage I larvae of crabs and shrimp.
Cessation of swimming was used as an index of sublethal response. Mortality
and behavioral responses were delayed. Behavioral responses were not observed
for 4 to 24 hours after the beginning of exposure, whereas measureable mortality
did not begin until 48-72 hours of exposure. The most toxic mud was a used mud
from the 3,382 meter depth in Cook Inlet, Alaska. It was a ferrochrome ligno-
sulfonate mud. The most sensitive species was the dock shrimp Pandalus danae
(Table 32). Acute toxicity, measured as 144-hr. LC50, ranged from 0.05 to 0.94%
whole mud suspension (500 to 9,400 ppm). Toxicity of water-soluble fractions
(WSF) of Cook Inlet mud (the aqueous fraction of a 1:1 seawater:drill ing mud
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97
Table 30. Relationship between drilling mud type, well depth and toxicity
of whole drilling muds to Arctic marine animals (From Tornberg
et al., 1980).
Drilling
Fluid Type
Well
Depth
Species
96-Hr. LC50 (ppm)
CMC/Gel
XC-Polymer
CMC/Gel/
Resinex
XC-Polymer/
Unical
1803 safron cod Eleginus navaga =235,000
1807 shrimp Mysis sp. . 215,000
2780 Arctic cisco Coregonus nasus . >200,000
2786 fourhorn sculpin Myoxocephalus quadrioornis >120,000
2778 Arctic Cisco C. nasus . =350,000
3057 Arctic cod Boreogadiis saida >250,000
3064 shrimp Mysis sp. 161,000
3064 fourhorn sculpin M. quadx-ioovnis 215,000
3065 shrimp 'Mysis sp. . =135,000
3319 fourhorn sculpin M. quqdricornis >200,000
3319 Arctic cisco C. nasus 64,000
3329 Arctic cisco C. nasus . 100,000
3646 shrimp Mysis sp. =75,000
3646 fourhorn sculpin M, quadrioornis - 75,000
2786 fourhorn sculpin M. quadricornis - 50,000
2786 shrimp Mysis sp. < 60,000
3466 shrimp Mysis sp. 73,000
3466 fourhorn sculpin M. quadricornis = 60,000
3785 amphipods Onisimus sp. &Boeckosimus . \ 381,000
3938 amphipods . 280,000
4029 . amphipods 278,000
4175 amphipods 241,000
4175 amphipods 221,000
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98
Table 31'. Acute toxicity of a used high density ferrochrome ligno-
sulfonate drilling mud to marine animals from Cook Inlet,
Alaska. LC50 values for whole mud bioassays are given
in ppm mud added (From Houghton et al., 19803).-
Species
No. of
Bioassays
Bioassay Dur-
ation (Hrs.)
LC50
Shrimp Pandalus hypsinotus
Amphipods Eogamrnarus oonfervicolus
Mysids Neomysis integer
Isopod Gnorimosphaer>oma oregonensis
Mussel Modiolus modiolus
Sculpin Leptoaottus armatus
Pink salmon fry Oncorhynchus gorbuscha
1
6
2
2
2
2
1
1
1
3
48
96
48
96
48
96
96
326
48
96
between 50,000 & 100,000
32,000-150,000
between 10,000 & 50,000
>70,000&>200,000
>74,000-=125,000
between 10,000 & 125,000
>70,000
>30,000
between 100,000 & 200,000
3,000-29,000
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99
Table 32. Toxicity to stage I larvae (less than 3 .days old) of shrimp
and crabs of a used ferrochrome lignosulfonate drilling mud
from Cook Inlet, Alaska. Toxicity was measured by mortality
(144 hr. LC50) and cessation of swimming (144 hr. EC50).
Bioassays were performed with whole mud-in-seawater suspen-
sions (SM) and water-soluble fractions (WSF) of drilling mud.
LC50, EC50 concentrations and their 95% confidence intervals
are given in ppm mud added by volume (From Carls and Rice, 1980),
Species
LC50
SM
WSF
EC50
SM
WSF
King crab
(Paralithodes oamtsohat-ioa]
Dungeness crab
(Cancer magister)
Tanner crab
(Chionoeaetes bairdi)
Kelp shrimp
(Eualus suckleyi)
Coonstripe shrimp
(Pandalus hypsinotus)
Dock shrimp
(Pandalus danae)
4,800 16,700
3,500-6,100 5,600-27,800
2,000 7,050
1,600-2,300 0-19,250
9,400 8,250
0-62,500 2,000-14,500
4,400 2,350
3,600-5,300 1,200-3,450
* 4,500
2,700-6,350
500
500-500
1,500
0-7,650
2,800 12,900
0-5,700 8,100-17,700
NC
NC
<5,000
NC
2,800
1,750-3,850
NC
4 2,000 3,250
2,300-4,150
500 1,050
200-800 800-1,450
*, not tested; NC, not calculable.
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100
mixture) ranged from 0.30 to 3.34% WSF (equivalent to 1,500 to 16,700 ppm
mud added). Behavioral responses were observed at slightly lower concentra-
tions. The shrimp larvae were more sensitive than the crab larvae to the
water-soluble extracts of the drilling mud. However, dungeness crab larvae
were more sensitive than kelp shrimp larvae to the whole drilling mud-seawater
suspension. This may indicate that dungeness crab larvae are sensitive to
high-suspended particulate concentrations.
The toxicity of the drilling mud WSF decreased slightly with time indicating,
as Neff et al. (1980, 1981) have suggested that volatile ingredients contribute
significantly to the toxicity of aqueous extracts of drilling muds.
The other five muds, which included used and unused Prudhoe Bay mud, used
and unused Homer spud mud, and used Homer mud, from 442 meters, were, with the
exception of the new Prudhoe Bay mud substantially less toxic to the larvae
than the used Cook Inlet mud (Table 33). The authors estimated..that 81+16%
of the toxicity of the drilling fluids was due to the particulate fraction of
the mud. The remaining 19% of the toxicity was attributed to the soluble
components of the mud. They also estimated that ferrochrome lignosulfonate
contributed most to the toxicity of the muds. Based on delayed response of
larvae to the drilling muds and the concentrations required to cause mortality,
the authors concluded that discharged drilling fluids would have little or no
deleterious impact on planktonic larvae of shrimp and crabs.
Summary of Acute Bioassay Results
In the acute bioas.says described ab.pye, toxicity of more than twenty
used offshore-type drilling fluids were evluated with 58 species of marine
animals from the Atlantic and Pacific Oceans, the Gulf of Mexico and the Beau-
fort Sea. Five major marine animal phyla were represented among the bioassay
organisms, including Chordata (8 species of fish), Arthropoda (31 species of
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101
Table 33. Comparative acute toxicity of six Alaskan
offshore drilling muds to stage I larvae
of king crab Paralithodes comtschatica and
coonstripe shrimp Pandalus hypsinotus. 144-hr.
LC50 values for the drilling mud water-soluble
fractions are expressed as ppm mud added (Data
from Carls and Rice, 1980).
Drilling Mud
Used Prudhoe Bay
New Prudhoe Bay
Used Cook Inlet
Used Homer spud
New Homer
Used Homer
Specific
Depth (m) Gravity (g/ml)
2,926 1.122
1.183
3,382 1.655
1.168
1,174
442 1.067
WSF 144-Hr. LC50 (ppm)
king crab
-
11,650
16,700
47,250
35,850
150,400
coonstripe shrimp
76,550
16,150
4,500
-
<25,000
188,100
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102
crustaceans), Mollusca (12 speci.es of molluscs), Annelida (6 species of poly-
chaetes), and Echinodermata (one species of sea urchin). Larvae and other
early life stages (considered to be more sensitive than adults to pollutant
stress) were included.
Although bioassay methods and conditions varied considerably, the results
were surprisingly consistent. All but a few of the 96-hr. LC50 values were
above 10,000 ppm drilling mud added. The lowest LC50 value was 500 ppm whole
mud for larvae of dock shrimp Pandalus danae exposed to a high density ligno-
sulfonate mud from Cook Inlet, Alaska (Carls and Rice, 1980). Other relatively
sensitive species included pink salmon fry Oncorhynchus gorbusaha^ lobster Homarus
amerioanus larvae, ocean scallops Plaoopecten magellan-icus* and mysid shrimp
(Mysidopsis3 Neomysis,, and My sis). The authors, in most cases, attributed the
sensitivity of these species to their intolerance of high suspended particulate
concentrations.
McFarland and Peddicord (.1980) examined the acute toxicity to several
species of Pacific Coast marine animals of suspended clay (Kaolin, median
particle size 4.5 ym). They found that organisms restricted to muddy bottoms
were very insensitive to high suspended clay concentrations. On the other hand
some species of open-water fish, fouling organisms, and sandy bottom epifauna
were relatively sensitive, though some species from these groups were quite
tolerant. The most sensitive species tested, the shiner perch Cymatogaster
aggregate*, had a 100-hr. LC50 of 6,000 ppm suspended clay. Eight species
experienced less than 10 percent mortality following exposure to suspended
clay for 5 to 12 days. These results are remarkably similar to those for
many of the drilling muds tested, suggesting that for some intolerant species,
damage is caused by mechanical abrasion or physical clogging of delicate
respiratory surfaces by fine particulates.
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103
Since mud aqueous fractions and liquid phase preparations were also
slightly toxic to some species, it is apparent that used drilling muds possess
some chemical toxicity and this is low (96-hr. LC50 greater than 10,000 ppm
mud added in most cases). The chemical and mechanical toxicity of the muds
appear, at most, to be additive or somewhat less than additive. There is no
evidence of synergistic interaction.
Chronic and Sublethal Effects
Rubinstein et al. (.1980) exposed mysid shrimp Mysidopsis bah-ia, oysters
Crassostrea virginica and lugworms Arenicola cristata to used drilling fluids
from Mobile Bay, Alabama (see Table 4) at nominal concentrations of 10, 30,
and 100 ppm for up to 100 days in a flow-through bioassay system. There was
17 percent mortality among mysids exposed to nominal concentrations of 30 and
100 ppm used mud for ten days. Lugworms had high mortalities after 100 days at
all drilling mud concentrations. There was 33 percent mortality at 10 ppm mud
and 75 percent mortality in 100 ppm mud. However, the design of the flow-through
exposure system was such that a layer of drilling mud accumulated on the surface
of the sand in the aquaria. At 100 days, this layer of drilling mud ranged from
4.5 mm at a nominal 10 ppm exposure concentration to 10.7 mm at a nominal 100
ppm exposure concentration. Thus a benthic infaunal organism like the lugworm
which feeds on surface sediments was actually exposed to very much higher con-
centrations of mud particulates than the nominal mud concentrations would imply.
This same argument could be used in reference to several of the static
bioassays with whole mud described above where mud particulates tended to settle
on bioassay organisms on the bottom of exposure tanks. The effect of this is
that actual exposure concentrations were higher than nominal ones, making
actual LC50 values higher than estimated. As indicated by the authors, the
apparent sensitivity of lugworms to drilling fluid could be due to intolerance
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104
to textural changes in substrate caused by accumulation of drilling mud
on and in the sand, or to chemical toxicity of some drilling fluid con- :
stiuents.
Exposure to the drilling mud also significantly inhibited rate of
regeneration of the shell in young oysters from a mean of 3.79 mm per week
among controls to 2.99 mm per week at a nominal 100 ppm drilling mud. As
indicated above, actual exposure concentrations were higher due to accumula-
tion of mud particulates.
Conklin et al. (1980) evaluated the acute and chronic toxicity and sublethal
effects of drilling muds collected at eighteen depth intervals from an explora-
tory well in Mobile Bay, Alabama. These were the same drilling muds as those
used by Rubinstein et al. (1980). None of the drilling muds was toxic to
intermolt grass shrimp Palaemonetes pugio at a nominal concentration of 10 and
100 ppm. Six of the drilling muds produced 30 to 60 percent mortality in 96
hours at a nominal concentration of 1,000 ppm (Table 34). One mud (#XVIII)
produced 100 percent mortality.
Inspection of Tables 4 and 34 gives some clues as to the apparent source
of the toxicity of some of the mud samples. Sample #1 contained primarily
barite, bentonite clay, caustic soda, soda ash and lignite, with small amounts
of SAPP, emulsifier and surfactant. Mud pH was 8.7. Only surfactant and SAPP
are considered at all toxic, so toxicity of this sample is unexplained. Samples
VIII and IX contained significant amounts of ferrochrome lignosulfonate, sodium
chromate and sodium bichromate which may have contributed to their toxicity.
SAPP concentration also was high. Sample XIII was heavily treated with ferro-
chrome lignosulfonate/sodium bichromate mixture (IMCO RD-111). Samples XVII
and XVIII were even more heavily treated with ferrochrome lignosulfonate and
inorganic chromate salts. In the six days prior to collection of sample XVIII, .
7,200 bbs ferrochrome lignosulfonate, 3,400 bbs sodium chromate, and 5,100 bbs
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105
Table 34.- Characteristics.of used drilling muds from different
depths of an exploratory drilling operation in Mobile
Bay, Alabama and acute toxicity (measured as percent
mortality at 96 hours at a nominal concentration of
1,000 ppm) of the whole muds to intermolt grass shrimp
Palaemonetes pugio (Data from Conklin et al., 1980;
Jones, 1980; Duke, personal communication).
Sample
No.
I
II
III
IV
V .
VI
.VII
VIII
IX
X
XI
XII
XIII
XIV
XV
XVI
XVII
XVIII
(ft.) . .
.Date of : Depth. Interval Specific Gravity
Collection (see Table 4) . at 20ฐC
1-31-79
11-13-79
III-6-79
111-12-79
III-20r79
IV-TO-79
IV-24-79
V-15-79
V-29-79
VI -6-79
VI -19-79
VII-5-79
VII-18-79
VII-24-79
VIIi;7-79
IX-4-79
IX-24-79
X-ll-79
4,600
5,900
5,974
6,814
8,698
12,465
14,423
14,607
14,657
14,598
15,100
16,230
17,376
18,023
19,075
20,459
20,715
21,114 '
1.205
1.132
1.175
1.135
1.155
1.139
1J89
. 1 .244 .
1.161
1.146
1.165
1.222
1 .279
1.322
1.320
1.738
1.629
1.492
Total iCr
(u9/g dry wt.)
55.0
52.4
41.4
35.4
47.8
472. .
662. '.
1,450
1,810
1,590
3,750
3,250
2,550
2,200
2,290
1,420
3,500 .
5,420
Toxicity
60
0
5
15
0
0
5
30
50
5
30
0
30
0
0
0
40
100
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106
sulfonated asphaltene lubricant-hole stabilizer (Soltex) were added to
the mud system and undoubtedly contributed to the toxicity of mud #XVIII,
The very high total chromium concentrations in these muds reflect the extent ; ..
to which they had been treated to counteract down-hole problems, mainly
high temperature.
Molting grass shrimp Palaemonetes pugio were more sensitive than inter-
molt shrimp to the drilling muds. The five most toxic drilling muds had esti-
mated 96-hr. LC50 values of 363 to 739 ppm. Mysid shrimp Mysidopsis bahia
were even more sensitive. Estimated 96-hr. LC50 for the most toxic mud
sample (.#XVIII) was 161 ppm. In a fourty-two day life-cycle bioassay in which
shrimp were exposed to dispersed mud in a flow-through system, estimated LC50
was 50 ppm whole mud. There was 25 percent mortality in 42 days at a nominal
drilling mud concentration of 10 ppm. The authors did not indicate whether '
drilling fluid particulates tended to accumulate in their flow-through exposure
system.
Derby and Atema (1981) studied the effects of two of the Mobile Bay drill-
ing muds (possibly #X and XVIII, though this cannot be ascertained with certainty)
on primary chemosensory neurons in walking legs of the lobster Homarus cmevicanus.
Exposure for 3-5 minutes to seawater suspensions of drilling mud at nominal
concentrations of 10 and 100 mg/liter (ppm) interferred with responses to food
odors in 29 and 44 percent, respectively, of the chemosensors examined. Groups
of lobsters were exposed to a 1 to 10 mm layer of drilling mud over natural
sediment in aquaria for 4 to 8 days. Chemoreceptors on the legs of these
lobsters were still able to respond to feeding stimuli, though percent of
chemosensors responding was lower than among unexposed controls. The authors
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107
mentioned unpublished data indicating that feeding behavior was suppressed
or abnormal in lobsters exposed to a 1-mm layer of drilling mud in a flow-
through exposure system.
Crawford and Gates (1981) described the effects of one of the Mobile
Bay drilling muds (collected shortly after sample #XI) on embryonic development
of the killifish Fundulus heteroclitus and the sand dollar Echinarachnius pcama.
Early development of F. heteroclitus was unaffected by concentrations up to 100
ppm mud, measured as dry solids (This corresponds to about 382 ppm whole mud.).
At 1,000 and 10,000 ppm (3,816 and 38,160 ppm whole mud) rate of development was
slowed, and at 10,000 ppm it was completely arrested. Heart beat rate of 14-32
day embryos was slowed by exposure to 1,000 and 10,000 ppm mud solids. Percent
hatching success was decreased at concentrations of 100 ppm and higher mud solids.
Sand dollar E. parma larvae developed normally at drilling fluid concjsnjra-^
tions up to 100 ppm mud solids. At 1000 ppm, development was delayed and 70
percent of plutei were abnormal. Sand dollar eggs treated with 1,000 or 10,000
ppm drilling mud had a low fertilization rate. Sperm were unaffected by drilling
mud treatment.
It is quite apparent that several of the used drilling muds from the
exploratory drilling operation in Mobile Bay, Alabama are quite toxic to marine
animals. Concentrations of these muds (particularly sample XVIII) producing
toxic or sublethal responses in sensitive species, life stages and biological
process of marine organisms are the lowest reported to date. Because these
C
muds were not intended for ocean disposaU-(-See-eomment-of Mr-.fcLE Yarbrough
foMowing the Rubtnsj^jn-e-1^a-lT-(1'98DO~pliperV""pTY3T)","yl't is difficult to
interpret the results in a proper environmental perspective. Some of the
drilling muds (especially the first 5) used in Mobile Bay are very similar
to drilling fluids which have been permitted elsewhere for ocean disposal.
Others are quite unusual, if not unique.
-------
108
Several other investigators: have studied effects of other used drilling
muds on growth and developmental parameters in marine animals. Concentrations
of 30 percent MAP (30,000 ppm mud added) or. greater of used seawater chrome
lignosulfonate drilling mud were acutely toxic to embryos of the killifish
Fundulus heterocHtus (Neff, 1980; Table 35). Most mortalities took place during
the first three days of development or at the time of hatching. Hatching success
was decreased significantly at MAP concentrations of 10 percent (10,000 ppm)
and higher. Newly hatched fry were extremely tolerant to the MAP. There was.
a dose-dependent increase in the incidence of developmental abnormalities in
drilling mud-exposed embryos. MAF-exposed embryos had a lower heart beat rate
and were shorter but heavier than controls at hatching. Percent total hatch of
fish embryos was decreased at all MAP concentrations examined.
Carr et al, (1980) reported that when early juveniles of mysid shrimp
Mysidopsis almyra were exposed continuously to 10-30 percent MAP (10,000^30,000
ppm mud added) of used seawater chrome lignosulfonate drilling fluid, there was
a significant decrease in food assimilation and net growth efficiency, resulting
in a reduction in growth rate. However, continuous exposure of larvae of grass
shrimp Palaemonetes pug-io for the duration of larval development to the mud
aqueous fraction of mid-weight and high weight lignosulfonate drilling muds had
no significant effect on development rate at concentrations that were not lethal
(Neff, 1980). Concentrations of 10-15 percent MAP (10,000 - 15,000 ppm mud
added) produced mortalities significantly higher than among controls.
Shell growth of spat of the oyster Crassostrea gigas was decreased slightly
but significantly during continuous exposure for six weeks to 5-20 percent MAP
(5,000-20,000 ppm mud added) of mid-weight and high weight lignosulfonate
drilling fluids (Neff, 1980). Condition index (ratio of dry meat weight to
dry shell weight) of surviving oysters was significantly lower among oysters
-------
Table 35. Summary of the effects of the MAP of used seawater chrome lignosulfonate drilling mud on
the early life history of Fundulus heteroclitus (From Neff, 1980).
Mud Aqueous Fraction (ppm mud added)
Parameter
% 96-hr, survival
(4-8 cell stage)
% 96-hr, survival
(1 day fry)
0
96
100
10,000 20,000 30,000
97 88 79
100
50,000
54
100
75,000
37
.
10,000
0
100
% of survivors expressing
growth anomalies at day
16
Heart rate at day 15
(beats per minute)
Day of first hatch
% total hatch
Total length at hatch (mm) 6.2
Dry weight at hatch (mg) 0.44356
Chromium concentration
in fry exposed con-
tinuously (ppm) 0.08-0.09
- 3.2
136.:7:
15
89
6.2
0.44356
27.1
121.5
17
63
5.7
0.46541
63.3
106.2
26
3
5.4
0.5789
76.9
102.3
30
1
93.1
88.9
--
--
--
100
__ O
0.07-0.09
-------
no
exposed to 5,000 ppm or higher concentrations of high weight lignosulfonate
drilling mud MAP than among controls.
In mussels Mytilus edulis exposed for 96 hours to the MAP (33-100 percent
equivalent to 33,000 - 100,000 ppm mud added) of three used chrome lignosulfonate
drilling muds, there was a tendency, not always statistically significant, for
filtration rate to be decreased, respiration rate to be increased and nitrogen
excretion rate to be increased (Gerber et a!., 1980). When mussels were exposed
to a suspended solids phase preparation of low density lignosulfonate mud at a
nominal suspended solids concentration of 50 mg/1 (corresponding to about 250 ppm
whole mud, assuming a total suspended solids concentration in the mud of about
20% by volume) for up to 30 days, shell growth rate was significantly depressed
after 10 days. Maximum growth rate depression relative to controls was 54
percent between 10 and 20 days. Low concentrations of suspended particulates
(up to 20 mg/ฃ silt) stimulate ingestion rate, assimilation efficiency and
growth rate of M. edulis (Kiorboe et al., 1980, 1981). However, higher concentra-
tions may interfere with feeding efficiency and thereby decrease growth rate.
Young scallops Placopecten magellanicus were more sensitive (Gerber et al.,
1981). When exposed continuously to the suspended solids phase preparation of
used mid-weight lignosulfonate drilling fluid for 40 days, growth rate of the
shells was reduced by 19 to 75 percent in comparison to control rate (Table 36).
Estimated total suspended solids concentration in the SSP preparation was 8.9
mg/ฃ (about 49.4 ppm mud added). Growth rate of small scallops was more
severely affected than that of larger animals. Growth inhibition was probably
due to interference by high suspended particulate concentrations with feeding
and assimilation efficiency. In experiments with the MAP of the same mud,
intermolt duration for larval stages of lobsters Eomarus americanus was
increased by about 3 days at a concentration of 2% MAP (2,000 ppm mud added).
-------
Table 36. Shell growth rate (mm/10 days) of the ocean scallop, Plaoopectin magellanicus ,
exposed for 40 days to the total suspended solids phase (SSP) of a medium-
density lignosulfonate drilling mud at 8.6 mg/ฃ in a flow-through bioassay.
Temperature increased from 5ฐC to 11.5ฐC over the exposure period. Each size
class was represented by six or seven scallops (From Gerber et al., 1981).
SIZE CLASSES (mm)
75.0-
70.0-
65.0-
60.0-
55.0-
50.0-
45.0-
40.0-
34.0-
29.0-
25.0-
80.0
74.9
69.
64.
59.
54.
49.
44.
39.
33.9
28.9
.9
.9
.9
,9
,9
.9
.9
Controls
0.15ฑ0.04
0.14ฑ0.03
0.10ฑ0.04
0. 1U0.02
-0.08ฑ0.06
0.10ฑ0.03
0.08ฑ0.03
0.10ฑ0.04
(0.07)*
0.10ฑ0.04
0.05ฑ0.02
Day^O to Day
Exposed
(0.09)*
0.08ฑ0.02
0.08ฑ0.03
0.06ฑ0.03
0.04ฑ0.01
0.0510.01
0.05ฑ0.02
0.04ฑ0.00
(0.03)*
0.02ฑ0.00
(0.016)*
GROWTH RATE
10
Percent Rate
Reduction
(40.0)*
42.9
20.0
45.4
7
50.0
37.5
60.0
(57.0)*
80.0
(68.0)*
(mm/10 days)
Controls
0.23ฑ0.03
0.17ฑ0.03
0.16ฑ0.04
0.1410.04
(0.07+0.02)
0.13+0.03
0. 1U0.04
0.1510.02
(0.10)*
0.1310.03
0.0810.03
Day 11 to
Exposed
(0.14)*
0.1310.04
0.1310.05
0.0910.03
O.lOiO.03
0.0810.02
0.06+0.03
0.0510.01
(0.04)*
0.0410.02
(0.02)*
Day 40
Percent Rate Reduction
(39.1)*
23.5
18.8
35.7
7
38.5
45.5
66.7
(60.0)*
69.2
(75.0)*
'*These values were estimated from the linear regressions presented in Figure 1 of this report.
-------
112
Gerber et al. (1980, 1981) examined changes in activity of two key
enzymes involved in energy metabolism as indicators of sublethal stress
in drilling fluid-exposed marine animals. Activity of enzymes, aspartate
aminotransferase (AAT) and glucose-6-phosphate dehydrogenase (G6PdH), were
either elevated or depressed in some tissues of exposed animals (Table 37
and 38). Minimum concentrations of drilling mud, either as a whole mud sub-
strate or as a MAP, eliciting responses were in the range of 16-33 percent.
Houghton et al. (1980a) reported that exposure of coonstripe shrimp
Pandalus hypsinotus to 100,000-150,000 ppm suspensions and pink salmon fry
Onoorhynchus gorbuscha to a 30,000 ppm suspension of whole used high weight
lignosulfonate drilling mud had profound histopathplogical effects on the
gill. Exposure to the drilling mud induced necrosis of the respiratory
epithelium and hyperplastic changes in certain cell types. Debris accumu-
lated within interlamellar areas. A concentration of 1,000 ppm drilling mud
was without effect.
Thompson and Bright (1977) studied the ability of three reef corals,
Diploria strig-osa, Montastrea caoernoso and Montastrea cnmulcarls, from the
East Flower Garden reef off the Texas-Louisiana coast to clear themselves of
a layer of used chrome lignosulfonate drilling mud. Twenty-five ml of a 1:1
seawater:drill ing mud slurry was applied to each coral colony. None of the
corals were able to clear their surfaces of this heavy application of drilling
mud.
In subsequent experiments, seven species of reef corals were exposed
for 96 hours to suspensions of a whole used freshwater ferrochrome ligno-
sulfonate drilling mud in aquaria maintained in 2-3 meters of water on a
sand flat at Carysport Reef off Key Largo, Florida (Thompson and Bright,
1980; Thompson et al., 1980). Three species, Montastrea annularis* Agariaia
agarioites and Acropora cervicornis, were killed by exposure to 1,000 ppm
-------
113
Table 37. Enzyme activities in the sand shrimp Crangon septemspinosa,
the green crab Carc-inus maenus, and the American lobster
Homarus americanus exposed for 96 hours for the mud aqueous
fraction (MAP) .of a used light-density lignosulfonate drill-
ing mud. Activity units are mean values in 0.001/min/mg
protein + one standard deviation; four to six. animals were
combined for analysis. Values for exposure concentrations
of MAP are ppm mud added. AAT = aspartate amin.otransferase;
G6PdH = glucose-6-phosphate dehydrogenase; BDL = below detec-
tion limits; S = level of significance where P < 0.05, Student's
t-test, values inside brackets are not significantly different
from controls (From Gerber e.t al., 1980).
Sand Shrimp
-Tฐ = 18C
Exposure
Concentration AAT G6PdH
Green Crabs
Tฐ = 8C
Am. Lobster*
Tฐ = 12C
AAT
G6PdH
AAT
G6PdH
0
10
33
66
100
,000
,000
,000
,000
BDL
' BDL
BDL
BDL
0.
0.
0.
0.
r
13ฑ0.05n
S
01ฑ0.01-l
05ฑ0.04
05ฑ0.02 .
2=0.26
BDL
BDL
BDL
BDL
0.04ฑ0
0.18ฑ0
0.33ฑ0
1.03ฑ0
r2=0.
.07-, 7
S 8
.06J
.10
.14 12
84
.13ฑ0
.65ฑ0
.44ฑ0
r2=0.
40Tc
.72
96
. 5.92ฑ0
' 2.77ฑ0
1.39ฑ0
0.1 6ฑ0
r2=0.
.70,.
.491S
.29
.05
69
* Activity is based on the heart tissue.
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114
Table 38. Enzyme activities* of the heart tissue of the northern
crab Cancer borealis exposed to the whole mud fraction
and the mud aqueous fraction of a medium-density ligno-
sulfonate mud for 96 hours at 5ฐC (From Gerber et al.,
1981).
Exposure Whole Mud Mud Aqueous Fraction
Concentration (%) AAT G6PdH AAT G6PdH
0
16
33
66
100
AAT = aspartate aminotransferase, G6PdH = glucose-6-phsophate dehydrogenase,
BDL = below detectable levels.
*Activity units are the mean values of five replicate analyses ฑ one standard
deviation of the mean in 0.001/min/mg protein.
4.53
7.77
9.35
13.34
21.02
r2
ฑ 0.
ฑ 1.
ฑ 1.
ฑ 0.
ฑ 1.
= 0.
79
10
64
97
88
98
0.
0.
0.
0.
0.
09
15
27
36
74
r2
+
+
+
+
+
=
0.
0.
0.
0.
0.
0.
04
06
12
16
23
94
5.
9.
11.
17.
02
20
67
35
r2
ฑ 0.
-
ฑ 1.
ฑ 1.
ฑ 1.
= 0.
94
34
72
64
98
0.
0.
0.
0.
12
18
25
62
r2
ฑ 0.05
-
ฑ 0.05
ฑ 0.09
ฑ 0.16
= 0.82
-------
115
whole drilling mud. At a nominal concentration of 100 ppm, these species
as well as Porites furcata and P. astreoides had a statistically significantly
higher percent polyp retraction than control colonies. A nominal drilling
mud concentration of 316 ppm was required to significantly increase percent
polyp retraction in Porites divariaata. Polyps of Diohoooenia stokesii, did
not respond to any drilling mud concentration.
Krone and Biggs (.1980) studied the effect of a suspension of 100 ppm of
a used drilling mud from Mobile Bay, Alabama (collected about the same time
as sample III; Table 34), alone or spiked with 3 or 10 ppm ferrochrome ligno-
sulfonate on oxygen consumption and ammonium excretion in the coral Madraeis
decatis. Respiration and excretion rates of corals exposed to 100 ppm drilling
mud alone were not markedly different from those of controls. Corals exposed
to the ferrochrome lignosulfonate-spiked drilling mud had elevated rates of
respiration and excretion during the first week of exposure. Much of the
difference was due to extreme responses of a few colonies which later became
moribund. The high degree of variability and small sample size per treatment
(n = 4) make it difficult to interpret the results. In addition, it is unlikely
that the ferrochrome lignosulfonate added to the drilling mud would be in the
same physical/chemical form as that in an authentic used ferrochrome lignosulfonate
drilling mud.
Small colonies of Montastvea annularis attached to cement tiles were placed
on the Carysport Reef in 3 meters of water (Hudson and Robin, T980a,b). A 2-4
mm layer of freshly prepared freshwater ferrochrome lignosulfonate drilling
mud was applied to the colonies 4 times at 2.5-hour intervals. The corals were
recovered 6 months later and growth rate was measured by X-ray radiography.
Growth rates of drilling mud-treated corals were slightly lower and less
variable than rates of control corals.
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116
It can be seen from the results discussed above, that in a majority
of cases, significant deleterious sublethal repsonses in marine animals are
observed at drilling fluid concentrations only slightly lower than those which
are acutely toxic. In the most sensitive species and life stages, such as
juvenile ocean scallops, lobster larvae, some reef corals, and mysid shrimp,
deleterious sublethal responses are observed during chronic exposure to whole
suspended drilling mud concentrations in the 50-100 ppm range. These species
and life stages appear to be very intolerant to prolonged exposure to high
suspended particulate concentrations. Damage is probably caused by abrasion
or clogging of delicate gill and gut epithelial surfaces.
Microcosm Studies
Various types of experimental microcosms have become popular in recent
years as links between laboratory experiments and field observations. Micro-
cosms have been used a few times to study the possible effect of drilling fluids
on marine benthic communities. Most of the marine invertebrates that spend
their adult lives on or in the bottom sediments have early life stages (larvae)
that float in the water column (are planktonic). When the larval forms approach
the time of metamorphosis, they seek out a suitable type of substrate and are
transformed into adult form. Since the adults usually have only limited loco-
motory ability, the planktonic larva is the main mechanism of species dispersal
and of recruitment each year of new animals to benthic habitats,. If drilling
muds deposited on or in natural substrates are toxic or change sediment texture
significantly, they might prevent some species from settling, changing the
composition of the benthic community. Tagatz et al. (1978, 1980) studied the
effects of a used lignosulfonate drilling mud, applied as a layer over clean
sand substrate or mixed with the sand, on recruitment of larvae to the substrate.
Natural unfiltered seawater flowed through aquaria containing the substrates.
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117
Recruitment of annelids and coelenterates was lower in aquaria containing
drilling fluid than in control aquaria (Table 39). Recruitment of arthropods
was diminished significantly only in aquaria containing a layer of 0.2 cm
drilling fluid on the sand substrate. Mollusc recruitment was unaffected.
Total number of animals recruited to drilling mud^treated aquaria was signi-
ficantly lower than the number recruited to control aquaria. Among the most
severely affected group, the annelids, most of the decrease in numbers of
individuals in drilling mud-containing aquaria was due to decrease in abundance
of one species, Armandia maculata, which was very abundant in the control
aquaria. Number of species of annelids present was unaffected at a concentra-
tion of 1 part mud to 10 parts sand, and dropped by a mean of about two species
per aquarium at higher exposure concentrations. Concentrations required to
elicit these responses were rather high; mud/sand mixtures of 1:10 and 1:5
(100,000 and 200,000 ppm drilling mud) or a layer of 2-mm mud on the sand.
Rubinstein et al. (1980) made similar observations in their studies of
the chronic toxicity of the controversial Mobile Bay used drilling muds.
In this case, molluscs were most severely affected. Numbers were greatly
diminished at a nominal 100 ppm drilling mud but their abundance was greater
than that in the control aquaria at nominal 10 and 30 ppm mud concentrations.
Polychaete worm and crustacean recruitment was affected only at the highest
mud concentration (100 ppm). It should be recalled that at this nominal
concentration in the flow-through system, a layer of more than 10-mm drilling
fluid particulates accumulated on the surface of the substrate during the
100-day timecourse of this experiment. This undoubtedly influenced settling
and survival of larvae. In the two investigations just summarized, the clean
natural substrate examined was sand. Since drilling fluids consist primarily
-------
118
Table 39. Numbers of animals and species (mean no. per aquarium)
collected from aquaria containing sand alone or sand-
chrome lignosulfonate drilling mud mixtures and receiving
unfiltered natural seawater at a flow rate of 200 ml/min
for 8 weeks (From Tagatz et al., 1978, 1980).
Taxon
Annelida
Armandia maculata
Mediomastus californiensis
Mollusca
Aoteocina canaliaulata
Laevocardium movtoni
Arthropoda
Corophiwn acherusicum
Coelenterata
Aiptasia pall-ida
Other Phyla
Total
Number
Control
276(7.8)
126
41
53(3.0)
23
16
36(1.8)
26
58(0.8)
58
6(0.2)
429(13.5)
of individual
Mud 1:10
174*(7.9)
55
21
39(3.0)
16
7
28(2.1)
14
13*(0.2)
13
4(0.1)
258*(13.8)
s or species
Mud 1:5
106* (5. 8*)
39
7
41(2.9)
19
5
44(1.9)
29
23*(.2)
23
5(0.1)
219*01.1)
.(in brackets)
ซ2-mm.Mud Cover
77*(5.1*)
3
19
27(1.8)
17
4
n*(o.8*)
5
4*(0.4)
4
0(0)
119*(8.0*)
*, significantly less than control at 5% level; significance is indicated
only for phyla.
-------
119
of clay-sized particulate material, mixtures of drilling mud and sand have
a different texture than sand alone. It is well-established that sediment
texture is a critical factor controlling choice of a suitable substrate by
planktonic larvae (Thorson, 1956, 1966). Thus, the responses observed could
be due to toxic effects of drilling mud or to changes in sediment texture.
Since some species prefer finer textured sediments, it is not surprising to
sometimes find a species more abundant in or restricted to the drilling mud-
containing sediment. So the effect of the admixture of large amounts of
drilling fluid with coarser natural sediments might be to change species
composition of benthic fauna in the affected area.
Gillfillan et al. (1981) took a slightly different approach. Trays con-
taining azoic (organism-free) mixtures of 0%, 33%, 66% and 100% of a used
high weight lignosulfonate drilling mud, seawater washed drilling mud, and
fine natural mud (similar in texture to the drilling fluid), were placed on
a soft bottom in 2.5 m of water in a Maine estuary for 84 days. After 84
days, animal communities found in trays containing drilling mud were slightly
more diverse than those in trays containing no drilling mud. However, popula-
tion density was much lower in trays containing 66 and 100 percent whole
or washed drilling fluid. The authors concluded that as much as 33 percent of
either whole or washed drilling fluid could be incorporated into the sediment
used with no reduction in population density and only a slight change in
diversity. Thus, it would appear that changes in sediment texture must be
considered in evaluating results of studies of this sort.
Interpretation of Bioassays in Relation to Field Observations
The results reported above show that for the majority of used offshore
drilling muds examined to date, concentrations lower than 10,000 ppm mud
added (greater than 100 to 1 dilution) are not likely to cause serious acute
damage to marine organisms. Sublethal or chronic effects are sometimes seen
-------
120
in sensitive species at 50^1,000 ppm whole mud. A mud dilution of 20,000
to 1 would render such muds nontoxic. During a high rate bulk discharge of
drilling mud at a rate of 1000 !bbfl /hr from an exploratory platform in the
Gulf of Mexico, the 20,000 to 1 dilution of drilling mud was reached about
150 meters downcurrent from the discharge (Ayers et al., 1980b).
It is extremely unlikely that any organisms in the water column in the
vicinity of a mud discharge will actually be exposed continuously to high con-
centrations of drilling mud for 96 hours (the length of time used in most
acute bioassays) and certainly not for 40-100 days (the length of some chronic
effects studies). As discussed above, during drilling, drilling mud and cuttings
are discharged intermittently and at highly variable rates. They are diluted
and dispersed in the water column rapidly.
However, there could !be a localized impact of drilling mud discharge on
benthic organisms and communities directly under and downcurrent from the
discharge where drilling mud and cuttings solids settle out. Changes may be
qualitative (species composition) rather than quantitative and may be only
temporary (months at most).
Field Studies
The few field studies published to date on effects of drilling mud
discharges on demersal, benthic and biofouling communities around offshore
exploratory and production platforms tend to corroborate conclusions derived
from laboratory studies; that ecosystem effects of drilling mud discharge to
the ocean are minimal and when detected of short duration.
Zingula (1975) reported that motile organisms were active on the surface
of cuttings piles under oil rigs even while drilling was still going on. He
suggested that colonizing organisms were able to rework the pile and turn it
into "normal" sea bottom within a few months.
-------
121
Gettleson (.1978) monitored health of reef corals on the East Flower ... ..
Garden Bank off the Texas-Louisiana coast before, during, and after drilling
of an exploratory well approximately 2,100 meters to the southeast of the
reef. Although some of the discharged mud and cuttings were distributed by
currents to a distance greater than 1,000 meters from the rig, none could
be detected in the coral reef zone. The drilling operation had no observable
effect on the coral reef.
Lees and Houghton (.1980) studied benthic communities in the vicinity of
the Lower Cook Inlet, Alaska, C.O.S.T. well before, during and after the
drilling operation. Some changes in benthic communities were seen near the
drilling platform during the course of the study. However, no statistically
significant differences could be attributed to effects of drilling operations
because of patchiness in faunal distribution, probably due to differences in
successional stages between areas sampled. They concluded that rates of
accumulation of drilling mud and cuttings on the bottom were not great enough
in the dynamic high-energy environment of Lower Cook Inlet to measureably
affect the benthic populations.
In a related study of the same drilling rig, Houghton et al. (1980a)
placed pink salmon fry, shrimp, and hermit crabs in live boxes at 100, 200,
and 1,000 meters downcurrent from the mud discharge. After four days, there
were no mortalities that could be attributed to the mud discharge plume.
Menzie et al. (1980) studied the short-term effects of drilling mud and
cuttings discharges on benthic communities around an exploratory drilling
platform in the Mid-Atlantic outer continental shelf off Atlantic City, New
Jersey. A zone of visible drilling discharge accumulations (primarily
natural clays) was observed in the immediate vicinity of the well site, while
elevated levels of clays were detected up to 800 m southwest of the site.
Fish and crab abundance increased substantially between the predrilling and
-------
122
postdrilling surveys in the Immediate vicinity and to the south of the well
site. These animals may have been attracted to the region by the increased
microrelief afforded by the cuttings accumulations. The cuttings had no
apparent effect on abundance of the sand star Astvopeaten amevicanus which
was the most abundant megabenthic species. In fact, large numbers of sand
stars congregated near the well site, apparently attracted by mussels Mytilus
edulis that had fallen from the drilling rig and anchor chains.
Within about 150 m of the discharge, sessile benthic animals like pennatu-
lid coelenterates (sea feathers) were subject to burial by drill cuttings.
However, within this zone there were patches of high abundance of macrobenthos.
Beyond the immediate vicinity of the discharge site, reduction in abundance
of macrobenthic organisms was attributed in part to increased predation by fish
and crabs and in part to increased clay content of the sediments. No correlation
was observed between abundance of marcobenthic organisms and barium content of
sediments or animal tissues. The affected areas extended to the southwest of
the well site for up to 800 m, in the direction of the prevailing currents.
The authors concluded that conditions in the benthos should return to the
predrilling state quite rapidly as bottom materials are reworked and resuspended,
and as new natural material is deposited.
Benech et al. (1980) studied fouling communities on submerged pontoons
of a semi submersible drilling rig off Southern California. Pontoons within
10 meters downcurrent of the mud/cuttings discharge had different fouling
communities than pontoons not exposed to drilling mud. Differences were
attributed primarily to mud sedimentation and not to light or exposure. Species
of algae sensitive to sedimentation and turbidity were eliminated from the
mud-exposed surfaces. With their disappearance, herbivorous invertebrates that
feed on them disappeared. Sediment-tolerant species became more abundant on
the mud-exposed pontoons. Effects were highly localized.
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123
We can conclude from the results of these publications that impact of
mud and cuttings discharge on benthic and fouling communities is related
to the amount of material .accumulating on the bottom under the discharge
pipe, which in turn is related to current speed and related hydrographic
factors. In high-energy environments, little mud and cuttings accumulates
and impact on the benthos is minimal. In low energy situations, more material
accumulates and there may be temporary reductions in abundance of certain benthic
species due to burial or incompatibility with clay. Other changes at the well
site not associated with mud and cuttings discharges often obscure effects of
the discharges. No evidence of chemical toxicity of drilling muds has been
observed in the field.
BIOAVAILABILITY OF HEAVY METALS
FROM DRILLING MUDS
Laboratory Studies
Water-based drilling muds, which are used in nearly 80% of offshore drill-
ing operations (Ray, 1979), are usually mixtures of clays, inorganic salts and
a variety of organic and metalloorganic compounds in fresh or salt water. Metal
composition of drilling fluids was discussed earlier in this review. Typical
concentrations of several metals in used drilling muds are listed in Table 41
and Appendix I, Tables 2.a-9.a. Elevated concentrations of barium, chromium,
zinc, cadmium, and lead, presumably derived in part from discharged drilling
muds, have been reported in the water and bottom sediments in the immediate
vicinity of offshore exploratory wells '(Ecomar, 1978; Crippen et al., 1980;
Gettleson and Laird, 1980; Mariani et al., 1980; Meek and Ray, 1980; Tillery
and Thomas, 1980; Wheeler et al., 1980; Trccine et al., 1981). The important
question relating to these metals is whether marine animals can accumulate them
in their tissues from the water or sediment to concentrations high enough to be
toxic to the animals themselves or a health hazard to human consumers of these
fishery products.
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Bioaccumulation of metals from two samples; of barite by two benthic
invertebrates, the hard shell clam neToencccia mercenar-ia and the sand worm
Nereis virens, was investigated by Espy, "Huston and Associates, Inc. (1981).
The bioaccumulation test protocol for dredge material was followed (EPA/COE,
1977). The animals were exposed for 10 days to a 1.5-mm layer of barite
over 3-mm clean sand in aquaria containing artificial seawater. Copper was
the only metal that increased in concentration in the overlying seawater during
the exposure period. The increase was very small. Neither species showed a
statistically significant accumulation of any of the metals.analyzed, zinc,
mercury, chromium, lead, cadmium, copper,and barium, during the 10-day exposure
period. Mean concentrations of copper and barium in polychaetes did seem to
rise slightly during exposure to barite. Because of small sample size (n = 3)
and variability in metals concentrations in both experimental and controls,
the differences were not statistically significant.
When grass shrimp were exposed to 50 mg/a barite in seawater (mostly as
a solid powder), they ingested the particulate barite (Brannon and Rao, 1979).
After one week exposure to barite, the shrimp contained whole-body residues of
9,134 mg/kg barium, compared to 26 mg/kg barium in controls. Most of this
was undoubtedly associated with particulate barite in the gut. When shrimp
were exposed for 106 days to 500 mg/ฃ, barite, barium accumulated in several
tissues, particularly the carapace. Exuviae cast off at the time of the molt
contained up to 19,987 mg/kg barium, compared to a maximum of 420 mg/kg in
exuviae of control shrimp. At the end of 106 days, hepatopancreas and carapace
of shrimp contained about 8,000 ppm barium, while muscle tissue contained
about 1,000 ppm. Thus, shrimp are able to accumulate barium from solid barite.
The barium tends to be sequestered with strontium in the calcium carbonate
skeleton. This barium is lost with the old exoskeleton at the time of the
molt. Barium is a normal trace component of carbonate skeletal structures in
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125
marine invertebrates (Chow and Snyder, 1980). Physiological effects of
barium accumulation in the shrimp are unknown.
Liss et al. (1980) s.-tudi.ed the concentrations of barium, chromium, iron
and lead in used drilling muds, in the liquid (soluble) phase of drilling
muds, in seawater suspensions of mud, and in the tissues of the sea scallop
Plaeopecten magellanious. Chromium, iron, and lead concentrations in the
liquid phase of whole muds-were higher than expected based on the solubility
of the respective hydroxides. Concentrations of barium and chromium in
solution in seawater suspensions of mud were also higher than expected.
These soluble metals apparently were complexed with soluble organic additives,
particularly lignosulfonates, in the mud. In scallops exposed for 27 days
to lg/ฃ of a used low density chrome lignosulfonate drilling mud from the
Baltimore Canyon, chromium concentration in the kidney rose to nearly 3 ppm,
compared to about 1.5 ppm chromium in controls. The slow adductor muscle,
the part of the scallop consumed by humans, did not accumulate any chromium.
When scallops were exposed to lg/ฃ of a synthetic attapulgite clay based mud
for 28 days, they accumulated up to 100 ppm barium in the kidney. Kidneys
of unexposed control animals contained a maximum of about 12 ppm barium.
No barium was accumulated in the adductor muscle.
Page et al. (1980) studied the accumulation of chromium from used off-
shore drilling muds by sand shrimp Crangon septemspinosus, sand worms Nereis
virens, and mussels Mytilus edulis. Sand shrimp accumulated nearly 2 ppm
chromium in their tissues during exposure for 96 hours to a 50% MAP of used .
low weight lignosulfonate drilling mud. Nearly all the accumulated chromium
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126
was released during 96 hours to clean seawater. Cadmium was not accumu-
lated from the mud by the shrimp. The sand worms failed to accumulate
chromium from the MAP or LSP preparations of used high weight lignosulfonate
mud. Mussels accumulated approximately 2-4 ppm chromium in their tissues
during continuous exposure for 30 days to a suspended solids phase prepara-
tion of used low weight lignosulfonate drilling mud containing 0.03 ppm
chromium. The mussels did not accumulate cadmium from the MAP of mid-weight
lignosulfonate mud and seawater chrome lignosulfonate mud.
Mussels were also exposed to several forms of chromium for up to seven
days (Table 40). Chromium in the MAP of the used mid-weight lignosulfonate
mud was the form least available for accumulation by the molluscs. Chromium
as the inorganic trivalent salt (Cr Cls) was the most readily accumulated
followed by chromium associated with ferrochrome lignosulfonate. These results
show that complexation of chromium with lignosulfonate decreases its apparent
bioavailability to mussels; and association of chrome lignosulfonate with the
clay fraction of the mud, as occurs in used chrome lignosulfonate muds (McAtee
and Smith, 1969; Knox, 1976; Liss et al., 1980), decreases the bioavailability
further.
Carr et al. (1981) examined the bioavailability of chromium from used
seawater chrome lignosulfonate drilling mud to three marine crustaceans,
PoTtunus spinicarpus3 Penaeus aztecus and Palaemonetes pugiof a.polychaete
worm. Nereis virens, and bivalve mollusc,, Rangia cuneata. All five species
showed an apparent accumulation of chromium during exposure to different types
of mud-seawater mixtures. When the crustaceans were returned to mud-free
seawater, they rapidly released the accumulated chromium. Clams R. cuneata
accumulated significant amounts of chromium when they were exposed to a sand
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Table 40. Accumulation of chromium by mussels Mytilus edulis
during exposure to chromium in different forms for
seven days (Data from Page et al., 1980).
Exposure Mixture
Cr in
Exposure Medium
(ppm)
Cr in Mussel Tissues
(pg/g dry wt.)
(ppm)
0 days 1 day 4 days 7 days
Seawater Control
MAP of Mid Weight Mud
Ferrochrome Lignosulfonate
Cr+3 so.lution (CrClJ
0.1
1.4
0.7
0.6
1.3
1.0
1.0
1.0
0.7
3.7
4.1
36.7
0.3
5.8
10.0
44.3
1.6
6.6
12.5
49.5
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128
substrate containing a layer of drilling mud (Figure 13). However, most of
the chromium was released within 24 hours when the clams were returned to
clean natural substrate, indicating that much of the chromium accumulated
was in the form of unassimilated mud components in the digestive tract or
on the gills. Clams and worms both accumulated chromium from the mud aqueous
fraction. The worms released the chromium more slowly than the clams did when
both were returned to clean seawater.
McCulloch et al. (1980) investigated accumulation of chromium, lead, and
zinc from the four used drilling muds, evaluated toxicologically by Gerber et al.
(1980, 1981) and Neff et al. (1980, 1981), by marsh clams Rangia cuneata and
juvenile Pacific oysters Crassostrea gigas. Concentrations of several metals
in the four muds is summarized in Table 41. As expected, chromium concentra-
tions were high in the three chrome lignosulfonate muds and low in the spud
mud. Copper concentrations were high in the MWL and HWL muds and lead and
zinc concentrations were unexpectedly high in all four muds.
Clams Pangia cuneata accumulated only small amounts of chromium and lead
from the mud aqueous fraction of mid-weight lignosulfonate mud. Less than
half the accumulated chromium and lead was released in four days when the clams
were returned to clean seawater. When juvenile Pacific oysters Crassostrea
gigas were exposed to the mud aqueous fraction of three drilling muds for two
weeks, they showed little or no net accumulation of chromium, lead or zinc.
.Maximum concentration of chromium accumulated, 7.53 ppm (approximately three
times the concentration in control animals), was in oysters exposed to the
40% MAF of mid-weight lignosulfonate drilling mud. Oysters exposed to the '
40% MAF of this mud also accumulated slightly more than 2 ppm lead in 14 days.
There was no net accumulation of zinc.from the MAF of any mud.
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20
ป' 18
16 -
14
o 12
o
I 10
o
c
o
0 8
h_
O
o
m
1 4
f
c
o
o
(b)
CLS mud (no clear)
CLS mud (24hr clear)
Reference sed. (24 hr clear)
j_
24
48
Time (hours)
72
96
Figure 13. Accumulation of chromium by the marsh clam
Rangia ouneata during exposure to reference
sediment from San Antonio Bay, Texas (contain-
ing 20.36 mg Cr/kg dry weight) and to a layered
solid phase preparation (LSP; 1:16 drilling mud:
seawater) of used seawater chrome lignosulfonate
drilling mud (containing 485 mg Cr/kg dry weight)
with or without a 24-hour period in clean sea-
water after exposure. Vertical bars represent
standard errors of mean for 10 clams.
a, significantly different from value for
clams in reference sediment at correspond-
ing sampling time at p < 0.005.
b. significantly different from correspond-
ing reference sample at p < 0.025.
c, significantly different from correspond-
ing reference sample at p < 0.05 (From
McCulloch et al., 1980).
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Mud
130
Table 41. Concentrations of several metals in four used drilling
muds as determined by flame atomic absorption spectro-
photometry. All concentrations are in mg metal/kg dry
mud (ppm), and standard deviation of two replicate
analyses. Values in parentheses are concentrations
determined by argon plasma emission spectrophotometry
(From McCulloch et al., 1980).
Drilling Mud
1
CLS
MWL
HWL
Spud
Cadmium 3.0ฑ0.7 (1.20) 19.2ฑ1.5 (15.86) 10.9ฑ3.5 (3.04) 3.5ฑ1.5 (7.23)
Chromium 485.2ฑ4.4 (395.0) 416.7ฑ8.5 (473.0) 224.9ฑ3.5 (287.0) 10.9ฑ0.5 (70.90)
Copper 48.2ฑ7.9 127.0ฑ8.5 118.8ฑ8.4 . 30.2ฑ3.3
Lead 179.4ฑ27.8 (68.57) 915.3ฑ45.7 (477.0) 209.5ฑ13.8 (124.6) 134.2ฑ20.9 (81.70)
Zinc 251.4+52.8 604.8ฑ13.1 274.5ฑ35.4 297.3ฑ1.6
1, CLS, seawater chrome lignosulfonate mud; MWL, mid weight lignosulfonate
mud; HWL, high weight lignosulfonate mud; Spud, spud mud.
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Rubinstein et al. (1980) reported elevated concentrations of barium,
chromium and lead in tissues of oysters following exposure for 100 days to
nominal concentrations of 10 to 100 ppm of the controversial drilling muds
from Mobile Bay, alluded to earlier. Mean concentrations of barium, chromium,
and lead in the drilling muds tested were 1,086, 1,372, and 41 yg/g (ppm),
respectively. One sample of mud had a chromium concentration of 5,420 ppm.
Oysters were placed in clean seawater for several hours before analysis to
allow purging of unincorporated mud particulates. Maximum metals concentrations
in oysters exposed to 100 ppm drilling mud were 56.17 ppm barium, 9.98 ppm
chromium, and 3.26 ppm lead, compared to levels of 1.90 ppm barium, 0.65 ppm
chromium, and 1.08 ppm lead in unexposed control oysters. It should be recalled
that mud particulates accumulated in the aquaria during exposure, so that actual
exposure concentrations were substantially higher than nominal values. Other
metals examined, including aluminum, iron and zinc, were not accumulated by the
oysters.
Tornberg et al. (1980) studied accumulation of cadmium, chromium, lead,
and .zinc by amphipods (Onisimus sp. and Boeckosimus sp.) during exposure for
up to 20 days to several dilutions of XC-polymer drilling fluids (heavy metal
composition summarized in Appendix I, Table 9a). Fifty sanimals were pooled
per sample and coefficients of variation between replicates were high. Mean
metal concentrations in control amphipods were 0.3 ppm (yg/g dry wt.) cadmium,
3.0 ppm chromium, 9.7 ppm lead and 85.8 ppm zinc. Metals accumulation was
neither dose nor time dependent. Maximum metal accumulation by the crustaceans
was approxiamtely 1.7 ppm cadmium, 5.3 ppm chromium, 20 ppm lead, and 140 ppm
zinc. So, in this case the greatest relative accumulation (nearly 6-fold) was
of cadmium. The other metals were accumulated 2-fold or less in 20 days.
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Gerber et al. (1981) studied accumulation of chromium by the ocean
scallop Placopeeten magellanious during exposure for 40 days to a suspended
solids phase (SSP) preparation or for 7 days to the mud aqueous fraction
(MAP) of a mid-weight lignosulfonate drilling mud (Table 42). Scallops
exposed to the SSP for 40 days contained about twice as much chromium as was
present in tissues of control animals. Accumulation of chromium by scallops
exposed to the MAP was dose-dependent. Maximum accumulation was to about three
times the concentration in control scallops. Scallops accumulated more chrom-
ium more rapidly from a 2% MAP than from an 8.6 mg/ฃ total suspended solids SSP
preparation, both of which contained the same concentration of chromium in the
aqueous phase.
These studies how that heavy metals associated with used drilling muds
have a limited bioavailability to marine animals. Chromium appears to be the
most readily accumulated of the mud-associated metals. Most of the chromium
in used drilling mud is associated with the high molecular weight lignosulfonate
fraction and with the clay. Organically bound and particle-absorbed heavy
metals usually are much less bioavailable than the metal ion in solution. Much
of the lead, zinc and possibly cadmium is in particulate form associated with
pipe dope (usually high in lead and zinc) and the clay or barite fractions of
the mud (McCulloch et al., 1980; Kramer et al'., 1980). Such tightly bound
metals generally cannot be assimilated by marine animals. These particulate
metals may be taken up from the digestive tract by phagocytosis (George et al.,
1976; Conklin et al., 1980). The metals are retained in intracellular vacuoles
and remain in particulate form. They may eventually be transferred to the kidney
and excreted. This may explain the observation of Liss et al. (1980) that
chromium and barium from drilling muds are accumulated in the kidney but not
the edible muscle of the sea scallop. The available evidence indicates that
there is little likelihood that heavy metals would be accumulated from
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Table 42. Bioaccumulation of chromium by the ocean scallop, Plasopeoten
magellanicus, exposed for 40 days to the suspended solids phase
(SSP) and for 7 days to the mud aqueous fraction (MAP) of a
medium density lignosulfonate drilling mud (From Gerber et al.,
1981).
SSP
Control Tank
8.6 mg/liter suspended solids
Concentration of Chromium ppm/q
In Solution In Tissues*
0.074
0.093
1.20
2.41
MAF
Control Tank
0.5%
2.0%
. 8.0%
33.0%
0.065
0.084
0.093
0.112
0.244
1.26
1.90
3.30
3.70
3.94
*Whole animals were ground and analyzed.
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134
environmentally realistic levels of used drilling muds in edible portions
of shell and finfish to concentrations that would pose a health hazard
to human consumers of such fishery products.
Field Studies
As indicated above, elevated concentrations of several metals have been
reported in the immediate vicinity of drilling platforms in the water column
during drilling fluid discharges and in bottom sediments following mud and
cuttings discharge. Heavy metals concentrations in the water column reach
background very quickly and within a short distance of the mud discharge pipe.
As discussed earlier, Ray and Meek (1980) estimated that trace metal concen-
trations reached background in the discharge plume within 200 meters of the
discharge pipe during mud discharge from a platform on Tanner Bank, California.
Ayers et al. (1980b) estimated that, in the drilling mud plume from a platform
in the Gulf of Mexico, trace metal, concentrations reached background levels
about 500 meters from the discharge source during a 275 bbl/hr. discharge and
about 1,000 meters from the discharge source during a 1,000 bbl/hr. test. Even
at the highest discharge rates, suspended solids concentrations reached back-
ground levels within 100 minutes. Thus, potential for accumulation of toxic
metals from drilling muds by water column organisms is minimal.
Several drilling mud associated metals tend to accumulate in bottom sedi-
ments in the immediate vicinity and downcurrent of the driling rig, where they
may persist indefinitely (Crippen et al., 1980; Gettleson and Laird, 1980;
Mariani et al., 1980; Meek and Ray, 1980; Tillery and Thomas, 1980; Wheeler
et al., 1980; Tracine et al., 1981). Thus, the important question becomes:
What is the bioavailability of these sedimented metals to benthic marine
animals?
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135
Mariani et al. (1980) studied changes in concentrations of several
metals in sediments and benthic invertebrates in the vicinity of an off-
shore exploratory rig in the Baltimore Canyon off New Jersey before and
after drilling. Elevations in only barium concentration in the postdrilling
sediment samples could be attributed to mud and cuttings discharges. Other
investigators have identified'barium as the major metal accumulating in
bottom sediments around drilling mud discharges (Chow and Snyder, 1980;
Gettleson and Laird, 1980; Wheeler et al.., 1980). This is not surprising
considering the high density and low solubility of barite and the large
amounts used in most .deep hole muds.
Mixed species assemblages of brittle stars, molluscs, and polychaetes
collected during the postdrilling survey, approximately two weeks after
drilling-related operations were termianted, had significantly elevated
concentrations of barium and mercury in comparison to animals collected in
the predrilling survey nearly a year earlier. The increase in mercury
concentration in the animals was unexplained. Mercury concentrations in the
discharged drilling muds and bottom sediments were below the limit of detec-
tion (<0.05 ppm) (Ayers et al., 1980a). The greatest apparent accumulation
of mercury was by the molluscs. Mariani et al. (1980) reported that predrilling
mercury concentrations in molluscs ranged from <0.009 to 0.665 ppm, and in
postdrilling samples, mercury concentrations ranged from 0.05 to 11.26 ppm.
Review by Mariani and associates of the analytical procedures and results
revealed computational errors in the postdrilling mercury data (Ayers, personal
communication). Recalculated range of mercury concentration in postdrilling
mollusc tissue samples was <0.006-0.58 ppm. Revised, corrected values for
mercury in postdrilling samples of brittle stars and polychaetes were in the
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136
<0.006 - 0.37 ppm range. So, apparently there was not a statistically
significant increase in mercury concentration between pre- and postdrilling
biota samples.
Concentration gradients of barium in benthic organisms were not correlated
with concentration gradients in bottom sediments. Polychaete worms had higher
concentrations of tissue chromium in postdrilling than in predrilling samples.
The other species did not accumulate chromium.
Crippen et al. (1980) measured concentrations of several metals in sedi-
ments, drilling muds and benthic animals from a drilling site in the Beaufort
Sea. Mercury, lead, zinc, cadmium, and arsenic were present at higher concen-
tration in the drilling mud than in the surface sediment. No correlation was
found between metal levels in the sediment near the mud discharge site and
levels in benthic infaunal organisms.
Tillery and Thomas (1980) reviewed several investigations of distribution
of heavy metals in sediments and biota in oil production fields in the Northwest
Gulf of Mexico. They reported concentration gradients of barium, cadmium,
chromium, copper, lead and zinc in surfacial sediments that decreased with
distance from some platforms. Trace metal concentrations in muscle tissues
of four commercially important species (brown shrimp Penaeus azteeus, Atlantic
croaker Micropogon unduldtus, sheepshead Archosargus probatocephalus, and
spadefish Chaetodipterus faber) generally were not significantly higher in
animals from the vicinity of oil production fields than in animals from other
regions.
As before, the results of the limited field studies to date tend to
corroborate the conclusions of laboratory studies. Accumulation of heavy
metals from sedimented drilling muds is very low, when it can be demonstrated
at all. Most of the metals of concern are associated with the barite and bent-
onite clay fractions of the drilling mud (Crippen et al., 1980; Kramer et al.,
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137
1980). The exception is chromium, which is associated primarily with
lignosulfonate. In a used chrome lignosulfonate drilling mud, much of the
chrome lignosulfonate becomes bound to the clay fraction (McAtee and Smith,
1969; Skelly and Dieball, 1969; Knox, 1976). Heavy metals which are in the
form of insoluble salts, are adsorbed to particulates, or are complexed with
organic solutes, usually have a much lower bioavailability to marine animals
than do the metal ions in solution (Jenne and Luoma, 1977; Neff et al., 1978;
Breteler et al., 1981). Page et al. (1980) showed that mussels Mytilus edulis
+3
accumulated more chromium from solution as Cr than from solutions of ferro-
chrome lignosulfonate or mud aqueous fractions of chrome lignosulfonate drill-
ing mud. Capuzzo and Sasner (1977) showed that chromium adsorbed to bentonite
clay was much less bioavailable to mussels Mytilus edulis and clams My a arenaria
than was an equivalent amount of chromium in solution as CrCl~. Neff et al.
(.1978) studied the accumulation of heavy metals from metal-contaminated sedi-
ments, five species of invertebrates, three salinities, and eight metals, a
significant accumulation of a metal was demonstrated only 36 times (26.5%).
In many cases where a statistically significant accumulation of a metal from
sediment occurred, the uptake was quantitatively marginal and of doubtful
ecological significance. Thus, high levels of a metal in a sediment or drill-
ing mud sample are not by themselves an indication of biological hazard.
These adsorbed metals have a very limited bioavailability.
One can conclude that benthic marine animals exposed to environmentally
realistic concentrations of used drilling muds in the sediment are unlikely to
accumulate sufficient mud-associated metals to represent a toxicity hazard
to themselves or to prey organisms, including Man. However, most laboratory
exposures have been of short duration. It is possible that a more substantial
metal bioaccumulation would be demonstrated following longer exposure periods.
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RECOMMENDATIONS
The volume of research on fate and effects of drilling fluids in the
marine environment, already completed or currently underway, is quite large.
Perusal of this leterature reveals some important gaps in our knowledge about
behavior of drilling fluids discharged to the marine environment. In addition,
same approaches to preventing or ameliorating drilling mud-mediated damage
to the marine environment become apparent.
1. Drilling mud and solids control equipment discharge
pipe design should be modified to maximize dilution
of drilling mud and cuttings before they exit the
pipe into the water column. A one-throusand fold
dilution of drilling mud at the point of discharge
should be readily obtainable.
2. The vast majority of offshore drilling muds are
completely non-toxic or nearly so. An effort should
be made to replace the more toxic muds and mud ingred-
ients with less toxic ones that still will perform
adequately. Mud toxicity should be included as a
consideration in drilling mud program design.
3. All new drilling mud ingredients and formulations
proposed for offshore use should undergo toxicological
screening before permitted for offshore disposal.
4. Drilling muds used in laboratory and field biological
effects studies should be characterized physically and
chemically. They should be muds that have actually
been used for a drilling operation. Major ingredients
should be known and trace metals concentrations should
be determined. The muds should be stored and used in
such a way that their properties do not change.
5. Muds used for laboratory and field biological effects
studies should be of types actually permitted for ocean
disposal. Use of prohibited muds, such as the controver-
sial Mobile Bay muds, confuses the whole issue. Little
information of direct predictive value is obtained.
Money and talent are wasted.
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139
6. Because.the major predicted impact of discharged
drilling muds is on the benthos and water column
effects are expected to be minimal, regulation of
drilling mud discharge rate seems inappropriate.
In fact, a very high rate bulk discharge may be
preferable since more of the mud will settle on the
bottom in the immediate vicinity of the discharge,
affecting a smaller area of bottom.
7. A flow-through exposure/bioassay system should be
developed which is capable of handling complex hetero-
geneous mixtures like drilling muds. Mud fractions
should not accumulate over time in any part of the
system. Doses should be reproducible and quantifiable.
3. Long-term studies of impacts of environmentally realistic
mixtures of drilling mud and sediment on benthic infauna
and epifauna should be performed. These could be labora-
tory large-scale microcosm studies or in situ studies
in and around drilling mud/cuttings piles.adjacent to
offshore exploratory rigs.
9. Coupled to the long-term biologicel effects studies,
should be investigations of metal bioavailability to
benthos from drilling mud-sediment mixtures. The .
question of the long-term bioavailability of metals to
the benthos from realistic levels of drilling mud mixed
with sediment is perhaps the most important single
question remaining about the environmental impact of
drilling muds.
10. Analytical methodology should be optimized for metals
analysis in all types of drilling mud fate and effects
studies. Mild digestion procedures do not adequately
solubilize metals associated with barium sulfate or
silicate minerals. Neutron activation is the method
of choice for barium and perhaps chromium. Some effort
should be made to ascertain the valency state and
chemical forms of chromium in used chromelignosulfonate
drilling muds and used chromate-treated lignosulfate
muds.
11. Additional research would be useful to elucidate the
mechanisms of drilling mud toxicity to very sensitive
species and life stages. Is it chemical toxicity (what
chemicals) or physical clogging, abrasion, or irritation
of delicate gill, gut or body wall surfaces? Such
information is useful for predicting the impacts of
drilling fluids discharged to the ocean.
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LITERATURE CITED..
Abel, P.O. 1974. Toxicity of synthetic detergents to fish and aquatic
invertebrates. J. Fish. Biol. 6^:279-298.
API. 1978. Oil and gas well drilling fluid chemicals. API. Bui. 13F.
First Ed., Aug. 1978, American Petroleum Institute, Washington,
D.C.
Ayers, R.C., Jr., T.C. Sauer, Jr., R.P. Meek, and G. Bowers. 1980a. .An
environmental study to assess the impact of drilling discharges
in the Mid-Atlantic. I. Quentity and fate of discharges. In:
Symposium on Research on Environmental Fate and Effects of Drill-
ing Fluids and Cuttings. Pages 382-418. Courtesy Associates,
Washington, D.C.
Ayers, R.C., Jr., T.C. Sauer, Jr., D.O. Stuebner, and R.P. Meek. 1980b.
An environmental study to assess the effect of drilling fluids
on water quality parameters during high rate, high volume discharges
to the ocean. In: Symposium on Research on Environmental Fate
and Effects of Drilling Fluids and Cuttings. Pages 351-381. Courtesy
Associates, Washington, D.C.
Beak Consultants. 1974. Disposal of waste drilling fluids in the Canadian
Arctic - Project C6006. Report submitted to Imperial Oil Ltd.,
Edmonton, Alberta, Canada. 170 pp.
Beckett, A., B. Moore, and R.H. Weir. 1976. Acute toxicity of drilling fluid
components to rainbow trout. Vol. 9. In: Industry/Government
Working Group in Disposal Waste Fluids from Exploratory Drilling
in the Canadian North. Yellowknife, N.W.T., Canada. 88 pp.
Benech, S., R. Bowker, and B. Pimentel. 1980. Chronic effects of drilling
fluids exposure to fouling community composition on a semi-submersible
exploratory drilling vessel. In: Symposium on Research on Environ-
mental Fate and Effects of Drilling Fluids and Cuttings. Pages 611-
635. Courtesy Associates, Washington, D.C.
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production platforms in the Gulf of Mexico. In: Symposium on Environ-
mental Fate and Effects of Drilling Fluids and Cuttings, pp. 562-587.
Courtesy Associates, Washington, D.C.
Tornberg, L.D., E.D. Thielk, R.E. Nakatoni, R.C. Miller, and S.O. Hillman. 1980.
Toxicity of drilling fluids to marine organisms in the Beaufort Sea,
Alaska. In: Symposium on Research on Environmental Fate and Effects
of Drilling Fluids and Cuttings, pp. 997-1016. Courtesy Associates,
Washington, D.C.
-------
151
Trefry, J.H., R.P. Trocine and D.B. Meyer. 1981. Tracing the fate of
petroleum drilling fluids in the northwest Gulf of Mexico.
Preprint from Oceans 81 Symposium. 5 pp.. (In Press).
Trocine, R.P., J.H. Trefry and D.B. Meyer. 1981. Inorganic tracers of
petroleum drilling fluid dispersion in the northwest Gulf of
Mexico. Reprint Extended Abstract. Div. Environ. Chem. ACS
Meeting. Atlanta, GA. March-April, 1981.
Ward, J.A. 1977. Chemoreception of heavy metals by the polychaetous
annelid Myxicola infundibulum (Salbeelidae). Comp. Biochem.
Physiol. 58ฃ:103-106.
Wheeler, R.B., J.B. Anderson, R.R. Schwarzer and C.L. Hokanson. 1980.
Sedimentary processes and trace metal contaminants in the Buccaneer
oil/gas field, northwestern'Gulf of Mexico. Environ. Geol. 3_:
163-175.
Wildish, D.J. 1972. Acute toxicity of polyoxyethylene esters and poly-
oxyethylene ethers to S. solar and G. ooeanious. Wat. Res. 6_:
759-762.
World Oil
1977. World Oil
completion gluids.
's 1977-78 guide to drilling, workover,
Gulf Publ. Co., Houston, TX.
and
Zingula, R.P. 1975. Effects of drilling operations on
ment. In: Environmental Aspects of Chemical
Operations, pp. 433-448. U.S. Environmental
EPA-560/1-75-004.
the marine environ-
Use in Well-Drilling
Protection Agency.
Zitko, V. 1975. Toxicity and environmental properties of chemicals used
in well-drilling operations. In: Environmental Aspects of
Chemical Use in Well-Drilling Operations, pp. 311-326. U.S.
Environmental Protection Agency. EPA-560/1-75-004.
-------
APPENDIX I
Drilling Mud Composition
-------
1-1
Appendix I.
Table 1.-
-Drilling Mud Systems Tested under EPA,
Region II Approved Joint Industry Bioassay
Program.
Mud #
Seawater/Potassiurn/Polymer Mud
Components
KC1
Starch
Cellulose Polymer
XC Polymer
Drilled Solids
Caustic
Barite
Seawater
Seawater/Lignosulfonate Mud
Components
Attapulgite or Bentonite
Lignosulfonate
Lignite
Caustic
'Barite
Drilled Solids
Soda Ash/Sodium Bicarbonate
Cellulose Polymer
Seawater
Lime Mud
Components
Lime
Bentonite
Lignosulfonate
Lignite
Barite
Caustic
Drilled Solids
Soda Ash/Sodium Bicarbonate
Freshwater
0.
0.
#/BBL
5-50
2-12
.25-5
.25-2
20-100
0.5-3
0-450
As Needed
#/BBL
10-50
2-15
1-10
1-5
25-450
20-100
0-2
0.25-5
As Needed
#/BBL
2-20
10-50
2-15
0-10
25-180
1-5
20-100
0-2
As Needed
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1-2
Appendix I.
Table 1. (Continued).
Mud
4. Nondispersed Mud
Components #/BBL
Bentonite 5-15
Acrylic Polymer 0.5-2
Barite 25-180
Drilled Solids 20-70
Freshwater As Needed
5. Spud Mud (slugged intermittently with seawater)
Components #/BBL
Attapulgite or Bentonite 10-50
Lime 0.5-1
Soda Ash/Sodium Bicarbonate 0-2
Caustic 0-2
Barite 0-50
Seawater As Needed
6. Seawater/Freshwater Gel Mud
Component #/BBL
Attapulgite or Bentonite Clay 10-50
Caustic 0.5-3
Cellulose Polymer 0-2
Drilled Solids 20-100
Barite 0-50
Soda Ash/Sodium Bicarbonate 0-2
Lime 0-2
Seawater/Freshwater As Needed
7. Lightly Treated Lignosulfonate Freshwater/Seawater Mud
Components #/BBL
Bentonite 10-50
Barite 0-180
Caustic 1-3
Lignosulfonate 2-6
Lignite 0-4
Cellulose Polymer 0-2
Drilled Solids 20-100
Soda Ash/Sodium Bicarbonate 0-2
Lime 0-2
Seawater to Freshwater Ratio 1:1 approx.
-------
1-3
Appendix I,.
Table 1. (Continued)
Mud #
8. Lignosulfonate Freshwater Mud
Components #/BBL
Bentonite 10-50
Barite 0-450
Caustic 2-5
Lignosulfonate 4-15
Lignite 2-10
Drilled Solids 20-100
Cellulose Polymer 0-2
Soda Ash/Sodium Bicarbonate 0-2
Lime 0-2
Freshwater As Needed
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1-4
Appendix I.
Table 2a. Muds Used in the Joint Bioassay Monitoring Program
MID-ATLANTIC BIOASSAY PROGRAM
. *Mud Number #2 - Seawater Lignosulfonate Mud
Composition
Components
Barite
Bentonite/Drill Solids
Chrome Lignosulfonate
Lignite
Drispac (Polyanionic cellulose)
Salt
Caustic
Concentration
*/bbl
176.0
32.1
1.8**
0.9**
0.2
10.0
0.9
Wt?
35.0
6.3
0.4
0.2
0.0
2.0
0.2
Properties
Mud Density
Percent Solids (wtป)
Calcium
12.1 Ibs/gal
43.5%
650 mg/1
Metals Analysis
Metal
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Vanadium
Zinc
Concentration (ppm-whole mud basis)
2.0
141,000
<1
227
11.3
< 1
< 1
7.5
18
181
*Flowline mud samples obtained from Ocean Victory, OCS-A-0028 #3 WC; operator-
Texaco. Collected March 16, 1980. Stored in refrigerator at EG&G until analysis
by bioassay contractors.
**Estiinated concentrations outside range for chrome lignosulfonate (2-15 r/bbl),
lignite (1-10 .#/bbl).
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1-5
Table 3a. Mid-Atlantic bioassay program.
*Mud Number 3 - Lime Mud
Composition
Comoonents
Barite
Bentonite
Drill Solids
Chrome Lignosulfonate
Lignite
Lime
Caustic
Concentration
#/bbl
64.0
20.0
30.0
3.5
1.8
1.5**
1.5
Wt%
14.7
5.6
6.8
0.8
0.4
0.5
0.3
Properties
Mud Density
Percent Solids (wt%)
PH
10.4 Ibs/gal
27.8
10.0
Metals Analysis
Metal
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Vanadium
Zinc
Concentration (ppm - whole mud basis)
3
' ' 76,200
< 1
192
8
4
-------
1-6
Table 4a. Mid-Atlantic bioassay program
*Mud Number 4 - Non-Dispersed Mud
Composition
Components
Barite
Bentonite
Drill Solids
Drispac (Polyanionic cellulose)
Lignite
10.8**
20.0**
49.0
1.0
0.1
Properties
Concentration
WtSc
2.8'
5.2
12.7
0.3
Metal
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Vanadium
Zinc
Mud Density 9.2 Ibs/gal
% Solids (by wt.) 21.0
Chlorides 1 ,200 mg/1
Metals Analysis
Concentration (ppm - whole mud basis)
2.0
13,300
< 1
10
7
2
< 1
4
22
16
*Flowline mud samples taken from Well No. 1, 6M&0 Railroad, WC/EUCUTTA Field,
Wayne County, Mississippi. Collected November 27, 1980 by PESA.
"Estimated concentration outside range for Barite (25-180) and Bentonite (5-15).
-------
1-7
Table 5a. Mid-Atlantic bioassay program
*Mud Number 5 - Seawater Spud Mud
Composition
Components
Barite
Drill Solids.
Bentonite
Lime
Soda Ash/Sodium Bicarbonate
Caustic
Concentration
l/bbl
2
52
22
0
0
0
.5
15.0
6.3
0
0
- 0
Properties
Mud Density
Percent Solids (by wt)
8.2
21.7
Metals Analysis
Metal
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Vanadium
Zinc
Concentration (ppm - whole mud basis)
3
2,800
16
5
6
35
21
*Flowline mud samples obtained Ship Shoal, Block 224, OCS6-10-23., Well D7,
Nobel-27. Collected October 23, 1980 by PESA.
-------
1-8
Table 6a. Mid-Atlantic Bioassay program
*Mud Number 6 - Seawater/Freshwater
Gel Mud
Components
Barite
Bentonite
Drill Solids.
Drispac (Polyanionic cellulose)
Cellex (CMC)
Caustic
Composition
Concentration
3/bbl
21.2
9.7**
14.1**
0.5
0.1
0.4**
Wt*
5.4
2.5
3.6
0.1
0.0
0.1
Properties
Mud Density
% Solids (by wt)
Chlorides
Calcium
9.3 Ibs/gal
11.6
250 mg/1
40 mg/1
Metals Analysis
Metal
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Vanadium
Zinc
Concentration (ppm - whole mud basis)
' 2
25,600
< 1
2
2
i
6
12
*Flowline mud samples taken from rig in Standard Draw Z-10, Carbon County, Wyoming.
Collected November 1, 1980 by PESA.
"Estimated concentration outside range for Bentonite (10-50), Drill Solids
(20-100), Caustic (0.5-3).
-------
1-9
Table 7a. Mid-Atlantic bioassay program
*Mud Number 7 - Lightly Treated
Lignosulfonate Freshwater/Sewater
Mud
Composition
Comoonents
Concentration
Drill Solids
Bentonite
Barite'
Chrome Lignosulfonate
Lignite
Cellulose Polymer (Drispac)
*7bb1
48
25
9
4
5
0.5
wt %
12
6.2
2.2
1.0
1.2
0.1
Properties
Percent Solids
Mud Density
PH
Chlorides
(wtS)
- 24.1%
9.6 Ibs/gal
10.8
7500 mg/1
Metal
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Vanadium
Zinc
Metals Analysis
Concentration (ppm-whole mud basis)
11,500
265
26
24
6
30
82
*Flowline mud sample obtained from Alaskan Star Drilling for Exxon USA in
Block 599 Exxon DCS A-0029 Well #1.
-------
1-10
Table 8a. Mid-Atlantic Monitoring Program
*Mud Number 8 - Lignosulfonate
Freshwater Mud
Composition
Components
Barite
Bentonite
Drill Solids
Chrome Lignosulfonate
Lignite
Caustic
Lime
Concentration
jVbbl
15.1
15.1
28.1
1.7**
2.8
1.2**
Trace
Vt%
3.9
3.9
7.2
0.4
0.7
0.3
.
Properties
Mud Density
% Solids (by wt)
Chlorides
pH
Calcium
9.3 Ibs/gal
16.4
1800 mg/1
9.0
40 mg/1
Metals Analysis
Metal
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
'Mercury
Nickel
Vanadium
Zinc
Concentration (ppm - whole mud basis)
3
14,000
< 1
48
4
9
< 1
8
18
15
*Flowline mud sample obtained from South Allenhorst Prospect, Caney Field,
C. R. Bos-twick and Brotherton Survey A-6, Matagora County, Texas. Collected
November 16, 1980 by PESA.
"Estimated concentrations outside range for Chrome Lignosulfonate (4-15),
'Caustic (2-5).
-------
Table 9a. Range of chemical and physical characteristics for the various types of drilling
fluids, and seawater used in bioassays.. Most metal concentrations were determined
by Flame AAS techniques. Barium was determined by graphite furnace AAS. Cadmium
in seawater was determined by ASV techniques. Detection limits for trace metals
are also indicated (From Tornberg et al., 1980).
mg/1
Drilling
Fluid Depth of Density
Type Well (m) (kg/1 ' pH Ba Cd Cr Cu Pb Hg Zn
a. drilling fluids
CMC/Gel
(2 samples) 1807-2653 1.21-1.23 10.0-10.5 4400-6240 ^0.5-0.6 28-63 6.4-10.4 2.4-12.8 0.017-0.031 42-64
XC-Polymer
(20 samples) 2784-3645 1.14-1.23 9.0-12.1 720-1170 ^0.5-1.5 66-176 10.0-16.0 5.6-56.0 0.015-0.070 49-110
XC-Polymer/
Unical
(6 samples) 3139-4175 1.21-1.32 10.0-11.0 N.A. N.A. 56-125 2.8-17.0 9-117 0.028-0.217 198-397
*
Lignosulfonate
Dri11i ng
Fluid
(4 samples) 2256-2692 1.15-1.23 10.0-11.0 800-7640 <0.5 121-17210.0-12.0 16.4-56.0 0.03-0.07 49-56
Detection Limit 0.10 0.5 2.0 2.0 2.0 0.010 2.0
b.. ambient seawater
Ambient
Seawater
(23 samples)* 7.9-8.4 <.0.02-0.04 ฃ.005-.019 iO.025 0.01-0.047 40.001 ฃ0.0002 10.010-0.068
Detection Limit 0>02 0.005 0.025 0.001
0.001 0.0002 0.010
N.A. not available
* n=3 samples for barium
-------
APPENDIX II
Ongoing Research Programs on Effects of Used
Drill.tag Muds on Marine Animals
-------
II-l
APPENDIX II. Ongoing research programs on effects of used
drilling fluids and drilling fluid ingredients
on marine organisms and ecosystems. Included
are investigations that were completed within
the last year and for which a final report was
not available to J.M. Neff. This list is not
comprehensive.
1. PI, Richard E. Dodge, Nova University: Sponsor, EPA. "Effects of Drill
Mud Effluent on Coral Growth: Montastrea annularis".
Corals were stained with Alizarin Red S and exposed for 50 days to
nominal 0, 1, 10, and 100 ppm drilling mud effluent. Drilling mud type,
source and exposure scheme were not described. Upward growth of coral
skeleton was depressed by long-term exposure to 100 ppm drilling mud
effluent. At this concentration, 2 out of 3 colonies died by 50 days'.
Other concentrations of drilling mud were without effect.on coral growth
and survival. Changes in coralite shape were variable at different
exposure concentrations. There was considerable variability in growth
parameters of both control and drilling mud-exposed corals.
2. PI, A. Szmant Froelich, Florida State University. Sponsor, EPA.
"Effects of Oil Drilling Muds on the Physiology and Nutritional Status
of Montastrea annularis".
Corals were exposed for six weeks to nominal 0, 1, 10 and 100 ppm
drilling mud. Drilling mud type, source and exposure scheme were not
described. At an exposure concentration of 100 ppm, respiration of corals
was decreased by approximately one-half and calcification rate was
decreased to one-tenth that of controls. Several corals exposed to 100
ppm drilling mud died. Abundance of symbiotic zooxanthellae in tissues
of corals exposed to 100 ppm drilling mud was significantly lower than
in controls, resulting in lower nitrogen fixation and gross photosynthesis
rates in mud-exposed colonies. Lower dirlling mud concentrations were
without significant effect.
3. PI, James W. Porter, University of Georgia. Sponsor, EPA. "Effects of
Drilling Fluids on Coral Respiration, Montastrea annularis".
Reports not available.
4. PI, Gerald Schatten, Florida State University. Sponsor, not known.
"Effects of Barium on Fertilization and Early Development in Sea Urchin
Embryos".
Barium sulfate in normal seawater and barium chloride in sulfate-
free seawater prevented normal fertilization and induced polyspermy in
eggs of the sea urchin Lytechinus variegatus. The author hypothesized
that trace barium ion interferes with calcium uptake by sperm during the
acrosome reaction, allowing polyspermy to occur. Barium ion concentrations
required to elicit this response were not measured.
-------
II-2
5. PI, Richard B. Crawford, Trinity College. Sponsor, EPA. "Effects of
Used Drilling Muds on Development of Fundulus heteroalitus, Edhinarachius
parma and Lytechinus variegatus".
Embryos were exposed to nominal concentrations of 1, 10, 100, and 1000
ppm used drilling muds from Mobil Bay, AL; Muds were collected on March 12,
April 24, May 29, June 26 and October 11, 1979. Results of experiments with
fish and sand dollar embryos were discussed in the main body of this review,
based on the publication of Crawford and Gates (1981). Eggs of the sea
urchin Lytechinus variegatus behaved similarly to eggs of sand dollars. At
a nominal 1000 ppm drilling mud, development was arrested at the blastula
stage. The October mud was the most toxic and the March mud the least toxic.
If unfertilized eggs were exposed to 10,000 ppm used drilling mud, subsequent
fertilization was inhibited.
In experiments with Fundulus embryos, 1000 ppm of the June 26 and
October 11 muds reduced hatching. The March 12 mud produced the same effect
at 10,000 ppm. The April 24 and May 29 muds were not toxic at any concen-
tration tested.
6. PI, Paul V. Hamilton, University of West Florida. Sponsor, EPA. "Effects
of Drilling Muds on Shell Movement in Argopeaten irradians".
Scallops were exposed to barite (IMCO-BAR"), chromate-treated chrome
lignosulfonate (IMCO RD-111), calcium carbonate or used Mobile Bay drilling
mud obtained August 7, 1979. Of five valve movement parameters measured
electronically, only two were considered reliable indicators of response
(change in number of major valve closures and change in cumulative valve
closure magnitude). Whole drilling mud significantly increased the number
of major valve closures at concentrations above 400 ppm and significantly.
increased the cumulative magnitude of valve closures above 200 ppm. Responses
to barite, lignosulfonate and calcium carbonate were similar to one-another
but different from responses to whole used mud. Maximal response to the
pure particulate compounds was observed at 200 ppm. Higher doses resulted
in lesser responses. The investigators suggested that behavioral responses
observed represented increased pseudofecal production by the scallops to
cleanse gills of accumulated foreign particles.
7. PI, Jelle Atema, Boston University, Sponsor, EPA. "Effects of Used Drilling
Muds on Lobsters Homarus americanus".
Some of the results from this program were discussed above (Derby
and Atema, 1981). Effects of exposure for 30.days in a flow-through system
to a nominal 10 ppm used drilling mud (designated J-5) or a natural marine
mud on stage IV postlarvae of lobsters was studied. Exposure to drilling
mud had no effect on survival but did result in increased loss of appendages,
apparently through difficulty in molting. The molt from stage IV to stage V
was not influenced by treatment but the subsequent molt from stage V to VI
was. There was a significant disruption and delay in molting among drilling
mud exposed animals. There was little or no effect of drilling mud on feed-
ing rate or feeding responses.
-------
II-3
Burrowing responses of lobsters to three muds (J.5, J7 and Mobile 16)
were measured. Lobsters preferred natural mud to sediment with a 1-mm
layer of J7 or Mobile 16 mud. J5 mud was without effect. A 1-mm layer
of drilling mud caused a delay in burrow construction and caused lobsters
to leave prexisting burrows. A 4-mm layer of Mobile 25 drilling mud
seriously interferred with burrow construction. A 4-mm layer of a barite/
bentonite mixture had the same effect on burrow construction as drilling mud.
Effect of exposure for up to four months in a flow-through system to
10 ppm of three used Mobile Bay drilling muds (collected May 29, June 26,
and September 4, 1979) on -survival and behavior of juvenile lobsters was
investigated. The drilling mud from June 26 was without effect on the
juvenile lobsters. Lobsters exposed to the other two muds showed a sub-
stantial loss of feeding behavior, both in slower alerting to the presence
of food and in a longer search time before finding food. These two drilling
mud samples produced 100% mortality in 15 days at a nominal 10 ppm drilling
mud. Whether mud components accumulated over time in the exposure system
was not discussed.
When lobsters were given a choice between clean natural mud substrate
and substrate overlain with 1-2 mm Mobile Bay used drilling mud, they always
chose the drilling mud-free substrate. When a layer of used drilling mud
was introduced to the "clean" side of the auqaria, the lobsters left their
burrow.
8. PI, Thomas R. Gilbert, New England Aquarium. Sponsor, EPA. "Impact of
Discharged Drilling Fluids on the Georges Bank Environment".
This is a multi-faceted investigation involving chemical characteriza-
tion of drilling muds used by several EPA drilling mud program investigators,
bioassay and sublethal effects studies with several species of marine
animals, and recruitment/recolonization studies. Several drilling mud
samples including Mobile Bay muds, "Jay muds", and API muds were analyzed
for physical and chemical characteristics, trace element composition, and
organic constituents. There were no consistent correlations between concen-
tration of inorganic components of muds and their toxicities. In some but
not all cases, muds high in dissolved chromium were more toxic than muds
containing low dissolved chromium concentrations. Several muds contained
diesel oil, and these were generally more toxic than those which did not
contain oil.
Bioassays were performed with several used drilling muds and the cope-
pods Acartia tonsa and Centropages typicus. Three drilling muds collected
from Mobile Bay on May 15, May 29.and September 4 had acute toxicities to
Acartia tonsa of 0.026, 0.091 and 0.61 ml mud/liter, respectively (equiva-
lent .to 26, 91 and 610 ppm mud added). If the preparations were allowed
to settle for one hour to three days before the bioassay, toxicity decreased
substantially to more than 1,000 ppm in all cases. Toxicity of the two May
muds appeared to be due primarily to settleable particles, while that of the
September mud was due primarily to soluble materials. Five used muds from
other sources had acute toxicities ranging from 2.4 to >10 ml mud/liter
(2,400->10,000 ppm). Centropages typious was about as sensitive as Acartia
to used drilling muds. Exposure concentrations only slightly lower than
acutely toxic concentrations were required to significantly reduce fecundity
in Acartia tonsa. Juveniles were no more sensitive to used drilling muds
than adults.
-------
II-4
Exposure for 96 hours of larvae of the ocean scallop Plaaopeoten
magellqniaus to 1-ml/liter (1,000 ppm) May 15 Mobile Bay drilling mud,
0.3 ml/ซ, (300 ppm) May 29 mud, or 0.1 ml/ฃ (100 ppm) September 4 mud
significantly inhibited shell formation. If surviving larvae were
returned to clean seawater after exposure, they were unable to recover
from arrested shell development. Drilling muds from other sources were
less toxic than the September 4 Mobile Bay mud to scallop larvae.
Larvae of the crab Cancer -Lrroratus were much more tolerant than
scallop larvae to the September 4 drilling mud sample. Exposure to
concentrations up to 100 yฃ/ฃ (100 ppm) had no effect on larvae survival
or molting. Stage III larvae exposed to 100 ppm drilling, mud initially
consumed Artemia nauplii at a higher rate than controls did. After 96
hours, mud-exposed larvae had a lower consumption rate than controls.
If allowed to recover in clean seawater, mud exposed larvae resumed normal
feeding. The 96-hr LC50 of the liquid, phase of used September 4 drilling ...
mud to 5-day-old Cancer larvae was 1.02 ml mud/liter (1,020 ppm mud added),
similar to the LC50 of this mud to Acartia..
Juvenile winter flounder Pseudopleuronectes americanus were unaffected
by exposure to 8.7 ml/ฃ (8,700 ppm) of May 29 drilling mud. Seventy-day-old
postmetamorphosis winter flounder were unaffected by exposure for 48 hours
to 1 ml/liter (1,000 ppm) of five drilling muds. Exposure of unfertilized
eggs of flounder to drilling mud had no effect on subsequent fertilization
and embryonic development in clean seawater.
Flounder larvae were exposed for 48 hours to 1 ml/liter suspensions of
five used drilling muds. Larvae seemed to exhibit avoidance behavior when
exposed initially to drilling mud suspensions. Some larvae exposed to two
Mobile Bay muds died. When returned to clean seawater, all surviving larvae
continued to survive and appeared normal.
Recruitment/recolonization studies were performed using several grain
sizes of natural sediment, ground silica and drilling muds. Deposition of
detritus from the flowing seawater was uneven in the circular tanks and
affected recruitment of planktonic larvae to the different substrates. There
was a tendency for control substrates to support larger populations than mud-
treated substrates. The system is being redesigned to provide more uniform
water flow. Field recruitment studies are also underway.
9. USN/NOAA. Sponsor, EPA. "Environmental Effects of Offshore Drilling and
Oil on the Marine Environment".
10. Yale University. Sponsor, EPA. "The Erodibflity of Drilling Muds Deposited
on the Sea Floor".
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