EPA-680/4-75-008
JULY 1975
Environmental Monitoring Series
MONITORING DISPOSAL-WELL
SYSTEMS
ENVIRONMENTAL MONITORING AND SUPPORT
LABORATORY-LAS VEGAS
US. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, Environmental Protection
Agency, have been grouped Into five series. These five broad categories were esta-
blished to facilitate further development and application of environmental technology.
Elimination of traditional grouping was consciously planned to foster technology trans-
fer and a maximum interface in related fields. The five series are:
J. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Series.
This report has been assigned to the ENVIRONMENTAL MONITORING series. This
series describes research conducted to develop new or improved methods and instru-
mentation for the identification and quantification of environmental pollutants at the
lowest conceivably significant concentrations. It also includes studies to determine
the ambient concentrations of pollutants in the environment and/or the variance of
pollutants as a function of time or meteorological factors.
EPA REVIEW
This report has been reviewed by the Office of Research and Development, EPA, and
approved for publication. Approval does not signify that the contents necessarily re-
flect the views and policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or recommendation for use.
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p
EPA-680/4-74-008
July 1975
MONITORING DISPOSAL-WELL SYSTEMS
by
Don L. Warner
Consulting Geological Engineer
Contract No. 68-01-0759
ROAP No. 22AAE
Program Element No. 1HA326
Project Officer
George B. Morgan
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas/ Nevada
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
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Effective June 29, 1975 the National Environmental Research Center-
Las Vegas "NERC-LV" was designated the Environmental Monitoring
and Support Laboratory-Las Vegas "EMSl-LV!1 This Laboratory is one
of three Environmental Monitoring and Support Laboratories of the Office
of Monitoring and Technical Support in the U.S. Environmental Protec-
tion Agency's Office of Research and Development.
It
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ABSTRACT
The U.S. Environmental Protection Agency is required, under P.L.
92-500, the Federal Water Pollution Control Act Amendments of 1972,
to establish a system for the surveillance of the quality of the nation's
surface and ground waters. Enactment of P. L. 93-523, the Safe Drink-
ing Water Act, further requires that State programs in order to be ap-
proved, shall include monitoring programs to prevent underground in-
jection which endangers drinking water sources. This report provides
information concerning the data needed for monitoring the subsurface
injection of wastewater through casedJ^p^alj^ls^a.ndjdiBcuBBes the
methods and tools available for obtaining the data. The procedures for
using the data for predicting the response of the receiving aquifer to in-
jection are then outlined. Surveillance of operating disposal wells is re-
viewed. Numerous examples are given throughout the text.
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ACKNOWLEDGMENTS
Mr. Charles F. Meyer, Dr. Richard M. Tinlin, and the late Dr.
Stephen Enke of General Electric—TEMPO were responsible for man-
agement and technical guidance of the project under which this report
was prepared.
The following officials were responsible for administration and tech-
nical guidance of the project for the Environmental Protection Agency:
Office of Research and Development (Program Area Management)
Dr. Henry F. Enos
Mr. John D. Koutsandreas
NERC—Las Vegas (Program Element Direction)
Mr. George B. Morgan
Mr. Edward A. Schuck
Mr. Leslie G. McMillion
Mr. Donald B. Gilmore
iv
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TABLE OF CONTENTS
EL
ABSTRACT ?ii
ACKNOWLEDGMENTS 5v
LIST OF ILLUSTRATIONS v11
LIST OF TABLES x
SECTION I - CONCLUSIONS ]
SECTION II - RECOMMENDATIONS 2
SECTION III - INTRODUCTION 3
SECTION IV - THE SUBSURFACE ENVIRONMENT 5
Stratigraphic Geology 5
Structural Geology ^
Uthology ] J
Fluids W
Mechanical Properties of Injection and Confining. Units 22
Hydrodynamics 29
Resources 30
SECTION V - ACQUISITION OF SUBSURFACE DATA 32
Prior to Drilling 32
During Well Construction and Testing 32
Rock samples 32
Formation fluids 35
Borehole geophysical logs 38
Testing of injection and confining units 44
Drill stem testing 45
Injectivlty tests 49
SECTION VI - PREDICTION OF AQUIFER RESPONSE 53
Flow Theory 53
Regional Flow %>
Pr««ur« Effect* of Injection 57
Rate and Direction of Fluid Movement 64
(continued)
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CONTENTS - Continued
Page
Hydraulic Fracturing^ 68
Generation of Earthquakes 70
SECTION VII - SURVEILLANCE OF OPERATING WELLS 72
Injection Well Monitoring 72
Periodic Inspection and Testing 76
Monitoring Wells 85
Other Monitoring Methods 88
SECTION VIII - REFERENCES 91
APPENDIX - EPA POSITION ON SUBSURFACE EMPLACEMENT
OF FLUIDS 97
vi
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LIST OF ILLUSTRATIONS
Figure No. Title
1 Generalized columnar section of Cambrian and
Ordovician strata in northeastern Illinois. 6
2 Isopach map of Mt. Simon Formation in northeastern
Illinois. 7
3 Schematic east-west section of the Eau Claire and
equivalent Rome strata. 8
4 Lithologic ratio map of post-Mt. Simon pre-Knox
rocks. 9
5 East-west cross section of Paleozoic rocks in the
northern Ohio River Valley. 10
6 Map of the Ohio River basin and vicinity showing
some major structural geologic features. 12
7 Structure on top of Mt. Simon Formation. 13
8 Isocon map, showing the dissolved solids content in
parts per million of water in the upper 100 feet of the
Mt. Simon Formation in Illinois. 15
9 Water viscosity as a function of temperature and
salinity. 17
10 Specific gravity of distilled water as a function of
temperature. 18
11 Specific volume of water as a function of temperature
and pressure. 18
12 Specific gravity of formation waters (Dw) versus total
dissolved solids. 19
13 Relationship between relative density and dissolved
solids content of brines in deep aquifers of the Illinois
basin. 20
14 Hydraulic pressure gradient in a column of water. 21
15 Compressibility of water. 23
(continued)
• •
VII
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ILLUSTRATIONS - Continued
je
Figure No*
16 Map showing distribution of the average porosity of
the Mt. Simon Formation in Illinois. 24
17 Reproduction of portfolio map No. 10, American Asso-
ciation of Petroleum Geologists Geothermal Survey of
North America. 28
18 Potentiometric surface of the Mt. Simon Formation in
Ohio and vicinity. 30
19 Sample log. 33
20 Fluid passage diagram for a conventional drill stem test. 36
21 Schematic illustration of various drill stem test conditions. 37
22 Portion of a Laterlog-gamma ray-neutron log from a deep
well in northern Illinois. 41
23 Portion of a sonic log from a deep well in northern
Illinois. 42
24 Portion of a temperature log from a deep well in northern
Illinois. 43
25a Normal sequence of events as recorded on the chart in
a successful drill stem test. 46
25b Sequence of events as recorded in a drill stem test when
no fluids were produced. 46
2^ Example of a plot of data from a drift stem test with dual
ciosed-in periods. 47
27 Plot of extrapolated pressure from drill stem test data
from an injection well in Ohio. 49
28 Plot of pressure buildup data from an inject!vity test of
the Mt. Simon Formation in Ohio. 50
29 Plot of recovery data and matching-type curves for an
injection test of a well at Mulberry, Florida. 52
30 Hydrogeology of the lower Floridan aquifer in northwest
Florida. 56
31 Generalized north-south geologic section through southern
Alabama and northwestern Florida. 58
32 Theoretical potentiometric surface of lower limestone of
Floridan aquifer in late 1971. 59
(continued)
viii
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CONTENTS - Continued
Figure No. Title
33 Generalized flow net showing the potential lines
and stream lines in the vicinity of an injection well
near an impermeable boundary. 63
34 Theoretical potent!ometric surface of the lower lime-
stone of the Floridan aquifer in 1971, with flow lines
showing the directions of aquifer water and wastewater
movement. 65
35 Predicted and probable actual extent of wastewater
travel for a well completed in a carbonate aquifer. 68
36 Schematic diagram of pressure versus time during
hydraulic fracturing. 70
37 Schematic diagram of an industrial waste injection
well completed in competent sandstone. 73
38 Pressure history of a well injecting into a carbonate
aquifer. 74
39 Semi logarithmic plot of two pressure fall-off tests
measured for an injection well of the Monsanto Com-
pany, Pensacola, Florida. 75
40 Monthly average injection index for two injection
wells of the Monsanto Company, Pensacola, Florida. 76
41 Pipe Inspection Log and photographs of casing pulled
after log was run. 78
42 Portion of a casing inspection log run in a wastewater
injection well showing apparent corrosion. 79
43 Preinjection and postinjection caliper logs from a
wastewater injection well at Belle Glade, Florida,
showing solution of the limestone aquifer in the 1500-
to 1600-ft interval by acidic wastewater. 80
44 Borehole televiewer log of a section of casing showing
casing perforations, packing seat and casing collar. 81
45 Borehole televiewer log showing vertical fractures in
the borehole wall of a well in Oklahoma. 82
46 Schematic diagram of a cement bond logging tool in
a borehole. . 83
(continued)
ix
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ILLUSTRATIONS - Continued
Figure No. Title page
47 Portions of a cement bond log from an acid wastewater
injection well. 84
48 Geologic column and construction of a wastewater
injection well at Mulberry, Florida, where two aquifers
above the injection zone are monitored through the
injection well. 39
LIST OF TABLES
Table No. Title
1 Typical description of a core from the top of the Mt.
Simon Formation in Illinois. U
2 Analysis of water from the Mt. Simon Formation in
the vicinity of Bloomington, Illinois. 16
3 Table of equivalency of permeability values. 26
4 Laboratory core analysis data from the Mt. Simon
Formation in Illinois. Oj,
O4
5 Welllogging methods and their applications. 39
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SECTION I
CONCLUSIONS
The subsurface environment is a complex one characterized by the
rocks and their structure, lithology, contained fluids and other resources,
and mechanical properties. The static and dynamic states of the rocks
and fluids are also characteristic of a region and a specific location.
An estimate of the characteristics of the subsurface environment can
be made prior to drilling of a well based on projections of data from out-
crops, previously drilled wells, and possibly surface geophysical studies.
A much more accurate knowledge of the local subsurface environment is
obtained when a well is drilled and tested. Data obtained from a well are
based on rock and fluid samples, geophysical logs, and pumping or injec-
tion tests.
When the characteristics of the subsurface environment have been
estimated or determined, the response to wastewater injection can be
predicted. Such predictions are essential to monitoring because they
provide a baseline of expected performance, including rate of pressure
buildup and rate and direction of travel of injected wastewater.
The principal means of injection-well monitoring is of the injection
well itself. This provides more protection than is commonly realized,
because the well is, in most cases, the most likely source of escape of
injected wastewater. Periodic inspection and testing of injection well
facilities complements continuous monitoring of well performance and
should prove helpful in detecting deterioration of these facilities prior
to failure.
Monitoring wells can be used for several purposes; they may be con-
structed in the injection aquifer, in or just above the confining beds, or
in freshwater aquifers. Local geology and hydrology, the waste being
injected, and economics are factors in determining if monitor wells are
needed, and, if so, how many and where.
Other types, of monitoring include surface geophysics, sampling of
springs, streams, and lakes, and monitoring to record any seismic events
which might be related to operation of the injection well.
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SECTION II
RECOMMENDATIONS
Monitoring of subsurface wastewaters injection should be thought of
as the full spectrum of consideration given to determining the effects of
a wastewater injection system from planning of the system through well
construction, testing, operation, and abandonment.
Policy guidelines of the Environmental Protection Agency and of The
Ohio River Valley Water Sanitation Commission (ORSANCO) should be
used as a basis for injection well monitoring. These sources also provide
suggestions for a suitable data base for monitoring and ORSANCO outlines
a series of administrative procedures that should be followed.
This publication provides a discussion of the tools and methods for
obtaining the needed data base and of the use of the resulting subsurface
data for prediction and interpretation of well behavior during operation
It also discusses the surveillance of operating wells in some detail The
maximum use should be made of the methods and tools that are available
consistent with the practicalities of available resources. Because of the
obvious complexity of many of the tools and methods, regulatory agencies
should not hesitate to request the assistance of other public agencies and
of prxvate consultants in monitoring injection systems
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SECTION III
INTRODUCTION
As of mid-1973, at least 278 industrial wastewater injection wells had
been constructed and 61 percent of them were operating (Warner and
Orcutt, 1973). This is a relatively small number of waste disposal units,
but the number has continued to increase at a rate of about 30 wells an-
nually and could increase even more rapidly in response to the objective
of eliminating discharge to surface waters and in response to demands of
new technologies such as geothermal energy production, desalination,
and radioactive waste disposal. Regardless of the number of industrial
wastewater injection wells, they have been an object of unusual attention
by regulatory agencies and by environmentalists.
This attention is reflected by inclusion of specific references to dis-
posal wells in Public Law 92-500, the Federal Water Pollution Control
Act Amendments of 1972. A provision of that Act is the requirement that
the Administrator of the Environmental Protection Agency shall, in coop-
eration with the States or other Federal agencies, establish a system for
the surveillance of the quality of surface waters and ground waters. The
enactment of Public Law 93-253, the Safe Drinking Water Act, further re-
quires the Administrator to propose and promulgate for State underground
injection programs minimum monitoring requirements to assist in prevent-
ing underground injection which endangers drinking water sources.
This publication provides technical information concerning data needed
for monitoring and the methods and tools available for monitoring of
wastewater injection wells and examples of their application. However,
the material presented cannot be expected to satisfy the monitoring re-
quirements of all aspects of underground fluid injection that will likely be
included in the rules and regulations that are promulgated in response to
P. L. 93-523. {The definition of the term underground injection is suffi-
ciently broad in P. L. 93-253 to include subsurface emplacement of fluids
by many means, such as ponds, pools, lagoons, and pits.} This publica-
tion relates specifically to the subsurface eiriplaceinent of fjgid^B tiiraugjb^
cased disposal wells. ~ '
To some, monitoring of ground water is often thought of as the observa-
tion of groundwater quality by sampling of wells and springs. In this pub-
lication, monitoring is meant to include the full spectrum of consideration
-------
INTRODUCTION
given to determining the effects of wastewater injection systems, from
planning of the system through well construction, testing, operation
and finally abandonment. The policy of the Environmental Protection
Agency is consistent with this approach (see Appendix; also, Hall and
Ballantine, 1973). ORSANCO (Ohio River Valley Water Sanitation Corn-
'1 * alS° haS established a basis
* injection well monitoring.
Both the EPA policy statement and the ORSANCO publication provide sue-
gestions for a suitable data base for monitoring. ORSANCO also sugeests
a series of administrative procedures, which, if followed, assure the
early involvement of regulatory agencies in monitoring and provide for
their continued surveillance of injection systems throughout construction,
use, and abandonment.
This publication is intended to complement existing ones, such as those
mentioned above, by providing a more extensive discussion of the data
that characterize the subsurface environment, of how these data are ob
tamed, and of how they are used to predict and interpret injection well
response. The surveillance of operating injection wells is also treated
in more detail here than in earlier publications.
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SECTION IV
THE SUBSURFACE ENVIRONMENT
In devising a monitoring program for a wastewater injection system,
the first consideration is definition of the regional and local subsurface
environment. Factors in such an appraisal are stratigraphic and struc-
tural geology, lithology, fluid properties, mechanical properties of injec-
tion and confining units, hydrodynamics, and subsurface resources. Other
publications (Warner, 1965 and 1968) have reviewed, in general, the rela-
tion of the subsurface environment to wastewater injection. The purpose
of the following discussion is to provide more specific detail and examples
of the methodology for applying these concepts to monitoring. It will be
attempted, insofar as possible, to avoid repetition of material that has
been previously presented.
STRATIGRAPHIC GEOLOGY
Regional stratigraphy is determined by use of outcrop and borehole
data which have been interpreted and are generally presented in the form
of columnar sections, isopach maps, facies maps, and cross sections.
The basic data unit used in studies of stratigraphic geology is the col-
umnar section, which is a graphic representation of the sequence, thick-
ness, lithology, and relationship of the rock units at a location. A gen-
eralized columnar section may be prepared, which shows these parameters
for a region. Figure 1 is a generalized columnar section for northeastern
Illinois. Columnar sections are prepared by using cores, cuttings, and
geophysical logs from boreholes and, where outcrops are present, from
them. Some possible injection horizons in Figure 1 are the St. Peter,
Ironton, Galesville, and Mt. Simon Formations. Of these, the Mt. Simon
is the deepest, and can be seen to be overlain by the Eau Claire Forma-
tion, which may contain confining shale beds. On the other hand, the St.
Peter Formation is shallower and is overlain by limestones and dolomites
which are less dependable as aquitards; and, therefore, the St. Peter has
a lesser potential for wastewater injection.
Isopachous maps indicate, by contour lines, the varying thickness of
a stratigraphic unit. Figure 2 is an isopachous map of the Mt. Simon
Formation in Illinois, showing that this sandstone unit varies in thickness
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THE SUBSURFACE ENVIRONMENT
SYS-
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LITHOLOGY
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Oolomitt and linw«iont, coortt groined;
\iholt, grttn
Sholt, dolomilic. brownish gray
Oolomitt, butt, medium grointd
Dolomitt.bjH. rtd Iptckltd
Oolomitt ond limtitent, buff
Oolomitt ond limtftont, gray mottling
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Dolomitt, brown, fin* grointd
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Sondttont, dolomitie
Oolomitt, nightly sondy; oolitic chtrt
Oolemitt. »ondy, oolitic ehtft
Oolomitt, slightly undy ot lop and
bost, light groy to light brown ;
gtodic quortz
Sond»ton«. dolomilt and sholt,
gtauconitic
Sondttont, mtdium grointd, dolomitie
in port
SOttlont, iholt, doiomilt, tondslon«,
glouconitt
Sanditant, lint lo eoortt gramtd
Figure 1. Generalized columnar section of Cambrian and Ordovician strata in north-
eastern Illinois (Buschbach, 19647 p. 16).
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STRATIGRAPHIC GEOLOGY
7 8 9 10 It R 12 E
46
LAKE
MICHIGAN
2000'
• Well penetrating complete
thickness of Mt. Simon
O Well reaching arkosic zone
but not base of Mt. Simon
Isopach, interval 100 feet
Miles
0 5 10 15
Figure 2. Isopach map of Mt. Simon Formation in northeastern Illinois
(Buschbach, 1964).
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THE SUBSURFACE ENVIRONMENT
from 0 to over 2, 000 feet within that State. Other factors being equal,
locations where the Mt. Simon Formation is thickest have greatest poten-
tial for wastewater injection.
The facies of a stratigraphic unit are its laterally varying aspects,
such as lithology, fossil content, and so forth. For example, the Eau
Claire Formation, which overlies the Mt. Simon Formation, consists
of a mixture of siltstone, shale, dolomite, and sandstone in northeastern
Illinois (Figure 1), but passes by facies change eastward into sandstone
in central Ohio and to dolomite in eastern Ohio (Figure 3).
Some types of facies maps are ratio maps, percentage maps, and iso-
lith maps. These facies maps are different ways of showing the relative
amounts of the various lithologies in a rock unit or units. The ratio and
percentage maps show contours of the ratios or percentages of the aggre-
gate thicknesses of lithologic classes.
Figure 4 is a lithologic ratio map, showing the relative ratios of sand-
stone, shale, and dolomite in post-Mt. Simon pre-Knox rocks in Ohio
This figure generally shows that this group of rocks changes from a sandy
facies in western Ohio to a dolomite facies in eastern Ohio. The rocks
depicted in Figure 4 are equivalent to the Eau Claire Formation in Fig-
ure 1. So, in eastern Ohio, the Eau Claire Formation is almost entirely
dolomite, rather than the mixed lithology shown in Figure 1. Without
further information, Figures 3 and 4 indicate that the Eau Claire Forma-
tion becomes less promising as a confining unit for the Mt. Simon For-
mation as it is traced eastward from Illinois into Ohio.
WEST
EAST
ROME FM (dolomite)
Rome sandstone facies
Figure 3. Schematic east-west section of the Eau Claire and equivalent Rome strata
IJanssens/ Ir/o, p. 10).
8
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STRATIGRAPHIC GEOLOGY
WW W - "•
sand-shale ratio
Figure 4. Lithologic ratio map of post-Mt. Simon pre-Knox rocks (Janssens, 1973, p. 19).
__. -• • _ _ j ^ _ A. — — MM. M«V£ M^«% **.•€ ^D-» 1 A**, rv^v j ** «*^v^*lf^ a i^i-^r+-^*^*H -v^ rt
Figure 5 is an east-west cross section of Paleozoic rocks extending
from east-central Illinois to northwestern Pennsylvania. This cross
section shows the facies changes in the Eau Claire that are described
above and shown in earlier figures. The cross section also shows that
the Mr. Simon Formation is about 1, 500 feet thick in east-central Illinois,
but thins to about 100 feet across northern Ohio and into northwestern
Pennsylvania. Thus, much of the same information conveyed in the pre-
vious figures is summarized in a readily understandable form in such a
cross section.
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CO
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m
m
z
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Figure 5. Easf-west cross section of Paleozoic rocks in the northern Ohio River Valley — modified after cross sections in
American Association of Petroleum Geologists cross section Publication 4, 1966 (Ohio River Valley Water
Sanitation Commission, 1973, p. 51).
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LITHOLOGY
Local stratigraphy is first projected from regional data before drilling
of a well, then determined in detail for the well when it is drilled. As
previously mentioned, the means of displaying the stratigraphy of a well
is the columnar section.
STRUCTURAL GEOLOGY
Structural geology means the folding, faulting, and fracturing of rocks
and the geographic distribution of these features. One means of showing
regional structural geologic features is a map which includes areas or
lines of major features. Figure 6 is such a map for the Ohio River Basin.
Another type of map is the structural contour map. Figure 7 is a struc-
tural contour map on the top of the Mt. Simon Formation in Illinois. Such
a map allows an estimate of the approximate depth to the mapped unit and
shows the location of known faults and folds that may influence decisions
concerning the location and monitoring of an injection well.
LITHOLOGY
Lithology refers to the composition and texture of a rock. The gener-
alized columnar section in Figure 1 contains brief, highly generalized
lithologic descriptions of rock units in northeastern Illinois. The descrip-
tions prepared for individual wells are very detailed. An example of a
description of a core from the top of the Mt. Simon Formation in one well
is shown in Table 1.
Table 1. Typical description of a core from the top of the Mt. Simon
Formation in Illinois.
Depth in Well
3019.4-3020.5
3020.5-3021.8
3021.8-3023.8
Lithologic Description
Sandstone; grayish-white; medium to very coarse
grained; grains are broken, pitted, and chipped;
very cohesive and hard; very tight; semi-quartzitic.
Sandstone; as above; very poor sorting; medium to
very coarse, rounded grains, with abundant fine-
grained matrix; glassy; slightly pyritic; cohesive
and hard; not as tight as above zone; limited mud
invasion.
Sandstone; good sorting; very fine to fine, sub-
angular grains; slightly pyritic; cohesive and
firm; limited mud invasion; very few shale
laminations.
11
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Figure 6. Map of the Ohio River twin anc! vicinity showing some major geologic features. Data modified
from published maps (Ohio River Valley Sanitation Commission, 1973, p. 24).
-------
LITHOLOGY
100
--3000-
TENN.
Contour, intervol 1000 ft
Kilometers
^^ rr^rft^r Fault, downthrown side indicated
Figure 7. Structure on top of Mt. Simon Formation (Bond, 1972, p. 36).
13
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THE SUBSURFACE ENVIRONMENT
Such detailed descriptions are prepared from cores, cuttings, and
geophysical logs, and are necessary for determining the rock-unit char-
acteristics in a test well. From such descriptions, and other data, in-
jection intervals, confining beds and casing points are selected and other
engineering decisions are made.
FLUIDS
Chemistry
Judgment as to whether wastewater may or may not be permitted to be
injected into a rock unit depends, in part, on the chemistry of the aquifer
water. The chemistry of aquifer water is also important because of the
possibility of reactivity with injected wastewater.
Policy concerning the minimum salinity of water in aquifers approved
for wastewater injection varies by State. In the Ohio Valley region,
Illinois agencies have determined that groundwater containing leas than
10,000 mg/liter total dissolved solids should be oroter.fp.fi- jn New York
waste injection is prohibited in aquifers with a dissolved solids content
of 2,000 mg/liter or less. In Florida, the limiting value is 1,500 mg/liter.
The problem of potential reactivity between wastewater and aquifer min-
erals and water is summarized by Warner (1968). Several recent papers
concerning this topic are contained in the Proceedings of the Symposium
on Underground Waste Management and Environmental Implications (Cook,
1972).
In order to evaluate the details of the chemistry of aquifer water it is
necessary to obtain samples after a well is drilled; samples from pre-
viously drilled wells may provide a good indication of what will be found
Geophysical logs are also useful for estimating the dissolved solids con-
tent of aquifer water in intervals that are not sampled, as will be discussed
later.
In Illinois, the Mt. Simon Formation has been found to contain water
ranging in dissolved solids content from less than 1, 000 mg/liter in the
northern part of the State to over 300, 000 mg/liter in the southern part.
Such information can be displayed in the form of an i so con map (Figure 8).
Most of the dissolved solids are sodium chloride, but significant amounts
ol calcium, magnesium, and sulfate are also present (Table 2).
Viscosity
Viscosity is the ability of a fluid to resist flow, and is an important
property in determining the rate of flow of a fluid through porous media.
14
-------
FLUIDS
Figure 8. Isocon map, showing the dissolved solids content in
parts per million of water in the upper 100 feet of
the Mt. Simon Formation in Illinois.
The common unit of viscosity is the poise, or the centipoise, which is one
one-hundredth of a poise. Figure 9 shows the variation in viscosity of
water with temperature and salinity. Both temperature and dissolved
solids content can have a significant effect. In most cases, the effects
will be offsetting in subsurface waters, since temperature and dissolved
solids content both tend to increase with increasing depth. The viscosity
of some waste waters may be unusually high as a result of the presence
of dissolved organic chemicals. Pressure in the range of interest has
an insignificant effect on viscosity.
15
-------
THE SUBSURFACE ENVIRONMENT
Table 2. Analysis of water from the Mt. Simon Formation in the
vicinity of Bloomington, Illinois.
Analysis
Specific gravity
PH
Hydrogen sulfide
Carbonate alkalinity
Bicarbonate alkalinity
Chlorides
Total hardness
Calcium
Magnesium
Sul fates
Manganese
Total iron
Total dissolved solids (calculated)
Result
1.050
6.6
0.0
0.0
68
39,250
17,900
5,200
1,190
1,700
1.3
27.0
65,460
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
Density
The density of a fluid is its mass per unit volume. The density of a
liquid increases with increased pressure and decreases with increased
temperature. However, the density of water changes very little within
the range of pressures and temperatures of interest. For example, the
density of water decreases only 0.04 gm/cm3 between 60°F and 210°F
(Figure 10), and increases only about 0, 04 gm/cm3 from 0 to 14, 000 psi
(Figure 11). A more important influence on the density of water is the
total dissolved solids content. Figure 12 shows the effect of various
amounts of sodium chloride on specific gravity (or density). * Since nat-
ural brines may differ significantly from sodium chloride solutions, it
may be desired to develop empirical relationships between density and
dissolved solids as was done by Bond (1972) for the Illinois basin (Figure 13).
*Specific gravity is the ratio of the mass of a body to that of an equal
volume of pure water, so for practical purposes, the numerical values
of density and specific gravity are equal. Specific gravity, however, is
is dimensionless.
16
-------
FLUIDS
180,000 PPM
240,000 PPM
68 100 150 200 250 300
RESERVOIR TEMPERATURE (*F)
350
Figure 9. Water viscosity as a function of temperature and salinity
(ppm NaCI) (Pirson, 1963, p. 40).
17
-------
THE SUBSURFACE ENVIRONMENT
8
UJ
UJ
UJ
cc
y
t
u
I.U IV
1.000
0.990
0.980
0.970
0.960
0.950
0.940
0.930
0.920
0.910
— ••
i™»
-=
^
•^X
X
x
^
X
\
\
s
N.
>,
s
\
k
\
40 80 120 160 200 240 280 320
TEMPERATURE, °F
Figure 10. Specific gravity of distilled water as a function
of temperature (Pirson, 1963, p. 39).
PROPERTIES OF LIQUID WATER
Figure 11. Specific volume of water as a function of temper-
ature and pressure (Eisenberg and Kauzmann, 1969.
p. 186).
18
-------
FLUIDS
a
u.
(ft
50,000 100,000 150,000
TOTAL SOLIDS (PPM)
200,000 250,000
Figure 12. Specific gravity of formation waters (D^) versus total
solids in ppm (data for NaCl solutions) (Pirson, 1963,
p. 39).
Pressure
A knowledge of fluid pressure in the unit proposed for wastewater
injection is important. Fluid pressure can be measured directly in the
borehole at the depth of the injection horizon, usually by performing a
drill-stem test, which will be described later. Fluid pressure at the
injection horizon can also be measured indirectly by determining the
static water level in the borehole, then computing the pressure of the
fluid column at the depth of interest.
Figure 14 shows how fluid pressure increases with depth in a well
bore filled with freshwater with a specific gravity of 1.0. When the aver-
age specific gravity of the water or wastewater is other than 1. 0 the rate
of pressure increase varies accordingly. For example, if a well bore
is filled with formation water with a dissolved solids content of 65, 000
mg/liter and a specific gravity of 1. 05, then fluid pressure increases at
a rate of 0.455 psi/ft, and would be 455 psi at the bottom of a 1, 000-ft-
deep water-filled well. The fluid pressure must be added to the pump
pressure in injection calculations to determine the total pressure.
19
-------
THE SUBSURFACE ENVIRONMENT
280,000
260,000 -
240,000 -
220,000 -
200,000 -
180,000 -
0 160,000 -
8
Q
> 140,000 -
120,000 —
100.000 -
80,000 -
60,000 -
40,000 -
20,000 -
1-00 1.02 1.04 ,.08 ,.08 ,.10 ,.„
RELATIVE DENSITY, p
Figure 13. Relation between relative density and dissolved solids content of
brines in deep aquifers of the Illinois basin (Bond, 1972).
20
-------
FLUIDS
^
1
1
Xj- 1 i
*/\
1
I
/r
i
,* —
i
A~
i
/T~
i
I
/!
1
i
>T-
^x 1
/T~
/
/ i
i
1
/| —
X i
/
Ft —
y
X
7
/
7
/
7
7
7
7
7
<"»•£/&
0.433
0433
0433
0 433
0.433
0.433
0.433
0.433
0.433
4.33 P*l"0
psi/ft
Figure 14. Hydraulic pressure gradient in a
column of water (Katz and Coats,
1968, p. 11).
Although instances of truly anomalous formation pressure are likely
to be relatively rare at sites selected for wastewater injection, the
existence of unusually high or low pressures and the possible reasons
for their existence should be recognized. Some causes of anomalous
pressure are:
1. Compaction of sediments
2. Tectonic forces
21
-------
THE SUBSURFACE ENVIRONMENT
3. Osmotic effects
4. Massive extraction or injection of fluids.
Abnormally high pressures can result from 1, 2, and 3 and from mas-
sive injection. Abnormally low pressures can result from osmotic effects
and extraction of fluids. Abnormally high pressures resulting from com-
paction of sediments are common in deep wells of the Gulf Coast (Dickinson,
1953). Berry (1973) concluded that abnormally high pressures in the Cal-
ifornia Coast Ranges are a result of tectonic forces. Hanshaw (1972) dis-
cussed natural osmotic effects and their relation to subsurface wastewater
injection.
Compressibility
The compressibility of an elastic medium is defined as;
where j3 = compressibility of medium (pressure'1)
V = volume
p = pressure
with dimensions
F = force
L,2 = area.
The compressibility of water varies both with temperature and pres-
sure as is shown in Figure 15. For problems in wastewater injection,
ft will generally be within the range of 2. 8 to 3. 3 X 1Q-& psi-l and
3. 0 x 10-0 psi-l is a reasonable value to assume in most case's.
MECHANICAL PROPERTIES OF INJECTION AND
AND CONFINING UNITS
Porosity
Porosity is defined as:
^ = v~ (dimensionless) ,,.
t * '
where 0 = porosity, expressed as a decimal fraction
Vv = volume of voids
Vt = total volume of rock sample.
Porosity is also commonly expressed as a percentage. Porosity may
be total porosity or effective porosity. Total porosity is a measur* £
all void space. In comparison with total porosity, effective porosity is
22
-------
MECHANICAL PROPERTIES OF
INJECTION AND CONFINING UNITS
PRESSURE-PSI A
1000
100
150 200
TEMPERATURE-°F
250
300
Figure 15. Compressibility of water (Katz and Coats, 1968, p. 93).
based on the total volume of interconnected voids. Effective porosity
better defines the hydraulic properties of a rock unit, since only inter-
connected porosity is available to fluids flowing through the rock. In the
remainder of the report, reference to porosity implies effective porosity
unless otherwise stated.
Porosity may also be classified as primary or secondary. Primary
porosity includes original intergranular or intercrystalline pores and the
porosity associated with fossils, bedding planes, and so forth. Secon-
dary porosity results from fractures, solution channels, and from re-
crystallization and dolomitization. Intergranular porosity occurs prin-
cipally in unconsolidated sands and in sandstones, and can be measured
reasonably well in the laboratory using core samples taken from wells.
Porosity contributed by fractures and solution channels is difficult to
measure in the laboratory. Various borehole geophysical methods that
will be discussed later can be used to determine the porosity of strata in
place. Porosity values in reservoir formations range from a maximum
of about 0.40 in unconsolidated sands to as little as 0. 02 in dense lime-
stones. Porosity in the Mt. Simon Formation of Illinois ranges from
about 0. 20 to 0. 02, as shown in Figure 16.
23
-------
THE SUBSURFACE ENVIRONMENT
POROSITY IN PERCENT
Figure 14.
dtorIb(jH •
24
-------
MECHANICAL PROPERTIES OF
INJECTION AND CONFINING UNITS
Permeability
Permeability is the capacity of a rock to transmit fluid. Permeability
is quantified by the coefficient of permeability or hydraulic conductivity.
When both the properties of the_fluid and the porous medium are considered,
the coefficient of permeability K is defined by Darcy's law as:
,L2) (3)
Apg dh (L >
where Q = flow rate through porous medium
A = cross- sectional area through which flow occurs r
ji = fluid viscosity
p = fluid density
L = length of porous medium through which flow occurs
h = fluid head loss along L
g = acceleration of gravity.
The unit of permeability used in oil field work is the darcy. Substitu-
tion of p = pgh into Equation 3 results in Equation 4:
K = f f ^
From Equation 4, the darcy has been defined as
1 cm3 /sec X 1 centipoise X 1 cm
1 darcy = -
1 cm x 1 atmosphere
A still simpler form of Darcy's law is used in groundwater studies
where the density and viscosity of water
K = (L/T) . (5)
A dh
The constant K is referred to as hydraulic conductivity and is usually
expressed with the dimenstions cm/sec (L/T) or in U.S. Geological Survey
units which are gallons/day x ft2 (meinzers). A table for conversion of
permeability units is given below (Table 3).
Permeability values for the formations used for wastewater injection
range generally from several darcys to less than a millidarcy (one milli-
darcy = 10~3 darcy). Average permeability values for the Mt. Simon
Formation in Illinois range from more than 100 millidarcys in the north
to less than 1 millidarcy in the south. The permeability of shale beds
25
-------
THE SUBSURFACE ENVIRONMENT
Table 3. Table of equivalency of permeability values
in various units (Davis and Deweist, 1966,
p. 165).
1 darcy
10-10 Cm2
0.1 cm/day
1.0 cirv/sec
1 darcy
1 me Inzer
= 9.87 x 10-9 cm-2 = 1.062 x 10"!
= 1.012x 10-12 darcys
= 1.15x 10-6 cm/sec « 1.18x 10"1] cm2
for water at 20° C
« 1.02 x 10"5 cm2 for water at 20°C
t* 18.2 meinzer units for water at 60°F
= 0.134 ft/day = 4.72 x 10'5 cm/sec «
5.5 x 10"2 darcys for water at 60°F
in the Eau Claire Formation, overlying the Mt. Simon Formation, is
consistently less than 0.001 millidarcy.
A useful constant in hydrogeologic work is the coefficient of transmis-
™ rT^i88^50 WhiCh " the Permeabil"y or hydraulic conductivity
multiplied by the thickness of the aquifer. When the unit of permeability
is the darcy, transmissivity is in darcy-feet/centipoise.
Compressibility
The compressibility of an aquifer includes the compressibility of the
£1athe • *•
where
C =
C =
0
(F/L2)
-1
(6)
compressibility of aquifer (pressure"1)
porosity
compressibility of water
compressibility of aquifer skeleton.
°
"
v ,
skeletons varies greatly,
discussed. The com-
-8
The coefficient used in analysis of reservoir response to injection or
pumpxng ,s the storage coefficient (storatlvity), which is defined b"°
-------
MECHANICAL PROPERTIES OF
INJECTION AND CONFINING UNITS
S = 0yb (0 + •?) (dimensionless) (7)
where 0 , /3, and a are as previously defined, and
S = storage coefficient
y = pg = specific weight of water per unit area
b = aquifer thickness.
The storage coefficient is the volume of water an aquifer releases or
takes into storage per unit surface area per unit change in hydraulic head.
The storage coefficient may be estimated from the equation above, or may
be determined from aquifer tests that will be described later. Values of
S are reported to range from 5 X lO'5 to 5 X 10~3 for confined aquifers.
As an estimate of the value of S for the Mt. Simon Formation in northern
Illinois assume that 0 = 11 percent, b = 1,700 ft, 7 = 0.45 psi/ft, ft =
3.0 X 10-6 psi-1, and* a = 6.7 X 10'^. Then, from the equation above,
S « 5.4 X 10-3. This is a high value, but the aquifer is very thick. If
the compression of the water alone were considered, then S would be
2.5 X 10-4. The Illinois State Water Survey (1973) estimated an average
storage coefficient of 1 X 10'4 for the Mt. Simon Formation in northern
Illinois, which is probably too low if the entire thickness of the formation
is considered.
Temperature
The temperature of the aquifer and its contained fluids is important
because of the effect that temperature has on fluid properties. The temp-
erature of shallow groundwater is generally about 2° to 3° greater than the
mean annual air temperature. In Illinois, this is from about 60°F in the
south to 50°F in the north. Below 30 to 60 feet, the temperature increases
approximately 1° to 2°F per 100 feet of depth. Figure 17 is a geothermal
gradient map of Illinois and Indiana. At a depth of 3, 000 feet, in northern
Illinois, the calculated temperature would be about 86°F. The measured
temperature at 3,000 feet near Pontiac, Illinois, was 90°F. Geothermal
gradient maps for the United States have been prepared by the American
Association of Petroleum Geologists (AAPG), Tulsa, Oklahoma, and can
be obtained from that organization. Figure 17 is a modification of one of
the AAPG maps.
*Testing of the Mt. Simon Formation, in a gas storage field in northern
Illinois, yielded a value of compressibility of the formation and its con-
tained water of about 7 X lO'6. Since the water only occupies 11 percent
of the rock, the rock skeleton compressibility at that location is 6. 7 X
10-6.
27
-------
THE SUBSURFACE ENVIRONMENT
FEET
TEMPERATURE DATA POINT
TEMPERATURE GRADIENT
t'Am FEET
I.2.J.6
1.6-2.0
>2.0
Figure
17. Reproduction of portfolio map No. 10, American Association
of Petroleum Geologists Geothermal Survey of North America
(Gould, 1974).
State of Stress
In order to predict the pressure at which hydraulic fracturing or fault
movement would be expected to occur, it is necessary to estimate the
state of stress at the depth of the injection horizon. On the other hand,
determination of the actual fracture pressure allows computation of the
state of stress (Kehle, 1964).
The general equation for total normal stress
medium is:
St = Po+Cri
across a plane in a porous
(8)
28
-------
HYDRODYNAMICS
where S^ = total stress
p0 = fluid pressure
Cfi - effective or intergranular normal stress.
Effective stress, as defined by Equation 8, is the stress available to
resist hydraulic fracturing or the stress across a fault plane that acts to
prevent movement on that fault. The equation shows that, if total stress
remains constant, an increase in fluid pressure reduces the effective
stress and a decrease in fluid pressure increases effective stress. When
the effective stress is reduced to zero by fluid injection, hydraulic fractur-
ing occurs. Fault movement will occur before normal stresses across the
fault plane are reduced to zero, since there must be some shear stress act-
ing on the fault blocks to cause them to move.
In a sedimentary rock sequence, the total normal vertical stress in-
creases with depth of burial under increasing thicknesses of rock and
fluid. It is commonly assumed, and the validity of the assumption can
easily be verified, that the normal vertical stress increases at an average
of about 1 psi/ft of depth. The lateral stresses may be greater or less
than the vertical stress, depending on geologic conditions. In areas where
crustal rocks are being actively compressed, lateral stresses may exceed
vertical ones. In areas where crustal rocks are not in active compression,
lateral stresses should be less than the vertical stress. The basis of esti-
mating lateral stress prior to drilling of a well is hydraulic fracturing data
from nearby wells and/or knowledge of the tectonic state of the region in
which the well is located. The tectonic state of various regions is only
now being determined. For example, Kehle (1964) concluded, as a result
of hydraulic fracturing data from four wells, that the stresses at the well
locations in Oklahoma and Texas were representative of an area that was
tectonically in a relaxed state. In contrast, Sbar and Sykes (1973) charac-
terized much of the eastern and north-central United States as being in a
state of active tectonic compression. Further discussion concerning the
state of stress and hydraulic fracturing will be presented in the section
on hydraulic fracturing.
HYDRODYNAMICS
Hydrodynamics, as the term has been adopted for use in subsurface
hydrology, refers to the state of potential for flow of subsurface fluids,
particularly in deep sedimentary basins. As examples of its application
recent publications by Bond (1972) and Clifford (1973) discuss the flow
potential in deep aquifers of Illinois, Indiana, and Ohio as determined
from pressure, water level, and water density measurements made in
deep wells.
The potential for flow in deep aquifers that are used for wastewater in-
jection is important, because it can be used to estimate natural groundwater
29
-------
THE SUBSURFACE ENVIRONMENT
flow rates and directions. Figure 18 is a map showing the potentiometric
surface of the Mt. Simon Formation Formation in Ohio and Indiana. The
arrows indicate the directions of regional groundwater flow in the Mt.
Simon Formation as indicated by the potentiometric contours. Bond
(1972 and 1973) discusses some of the difficulties in interpretation and
application of potentiometric data.
RESOURCES
An objective in the monitoring of subsurface wastewater injection is
to verify that fresh groundwater, oil or gas, coal, or other subsurface
resources are not being jeopardized. Therefore, the occurrence and
distribution of all significant subsurface resources must be determined.
This determination is made by reference to published reports and by
consultation with public officials, companies, and individuals familiar
with subsurface resources of the area. Also, the actual drilling of the
well will show the location and nature of resources present at depth at the
well site.
In reviewing the occurrence of subsurface resources, the locations,
construction, use, and ownership of all wells, both shallow and deep
within the area of influence of the injection well should be determined.
The plugging record for all abandoned deep wells should be obtained to
Altitude ol potentiomeutc surface above s«a level
(contour interval 200 feet, dashed where inferred)
Inferred direction ol flow
Figure 18. Potentiometric surface of the Mt. Simon Formation
In Ohio and vicinity (Clifford, 1973).
30
-------
RESOURCES
verify the adequacy of such plugging. In States where oil has been pro-
duced for many years there are often areas where wells are known to
have been drilled, but for which no records are available, and there are
also wells which are located but for which plugging records are not avail-
able or for which plugging is known to have been inadequate. Document-
ing the status of deep wells near the injection well may be the most impor-
tant step in monitoring of injection wells in areas that are or have been
active oil or gas provinces, because these wells provide the greatest
hazard for escape of wastewater or formation water from otherwise well-
confined aquifers.
31
-------
SECTION V
ACQUISITION OF SUBSURFACE DATA
PRIOR TO DRILLING
In order to estimate the performance of injection wells and to evaluate
the subsurface environment prior to construction, the types of information
described in Section IV, The Subsurface Environment, are estimated from
sources such as the figures and tables from that section. The information
in those figures and tables has, of course, come from previously drilled
wells; and if it has not been compiled on maps, cross sections, and tables,
then this may be necessary before it can be used. Basic information for
previously drilled wells is available in most States through State geological
surveys, oil and gas agencies and water resources agencies. In addition,
private companies acquire and sell well logs, and other subsurface data.
In some cases it may be necessary to go to individual oil companies or
consultants for subsurface data that are not publically available. Com-
panies and individuals are usually cooperative in releasing information
that is not considered confidential.
DURING WELL CONSTRUCTION AND TESTING
Rock Samples
Most deep wells drilled today are drilled by rotary drilling rigs Ro-
tary drilling rigs use two basic types of drilling bits, rock bits and core
bits. Rock bits grind the strata into small chips that are usually carried
from the hole by a viscous drilling mud, but sometimes by water or air
The chips are periodically collected, usually after each 5 or 10 feet of
new hole, washed, and examined with a low-powered binocular micro-
scope. The methods for collection, examination, and description of such
samples are presented in a reference edited by Haun and LeRoy (1958)
Figure 19 is an example of a sample log prepared by examination of cut-
tugs. Soft, unconsolidated clays will not yield chips, but will break down
into mud and unconsolidated or soft sandstones into individual grains when
drilled. Samples are of only limited value in such areas.
Cores taken with rotary core bits and barrels give a much more accur-
ate picture of the subsurface formations than cuttings, but core samples
are very expensive (>$50/ft) in deep wells and can usually only be afforded
in limited numbers. In deep wells, core samples are commonly about
32
-------
DURING WELL CONSTRUCTION
AND TESTING
Pe fining
NO.
I/lustration >*«*
GMrfit/d «». Oklmhomm *rsn
12 3f
y _
Rotmry too/±_
Discovery Welj^
LEGEND
&W
LimMtonc
. w/eh«rt
IMS I N» Sample
| Oil Main
Figure 19. Sample log
(Moore, 1951).
33
-------
ACQUISITION OF SUBSURFACE DATA
four inches in diameter. Cores are described just as are cuttings, but
since a continuous sample of the formation is available, a detailed foot
by foot description can be prepared (Table 1). Whole-core samples can
be analyzed for porosity and permeability in the laboratory, or small
cores can be taken from the large core and analyzed. The latter proce-
dure is the most common. Table 4 shows typical laboratory core data
from the Mt. Simon Formation in Illinois.
Table 4, Laboratory core analysis data from the Mt. Simon
Formation in Illinois.0
Sample
Number
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
Depth
(feet)
3154.5
3155.5
3156.6
3157.5
3158.5
3159.5
3160.5
3161.5
3162.5
3163.5
3164.5
3165.5
3166.5
3167.5
3168.5
3169.5
3170.5
3171.5
3172.5
3173.5
3174.5
3175.5
3176.5
3177.5
Permeability
(millidarcys)
Horizontal
6.9
<0.10
<0.10
0.17
0.26
<0.10
1.9
<0.10
2.3
0.43
12.
3.1
0.31
7.8
8.5
5.0
6.2
3.4
10.
1.4
11.
8.5
2.6
0.74
Vertical
0.11
0.17
<0.10
0.31
0.72
<0.10
0.12
<0.10
0.98
0.46
0.12
1.1
0.44
0.79
5.4
3.2
3.6
1.2
2.5
0.46
2.0
1.5
0.91
<0. 10
Note:
Porosity
(percent)
6.4
6.4
9.7
8.6
8.3
8.1
9.6
8.7
8.1
6.2
8.2
14.7
10.7
10.0
9.9
7.2
6.9
8.3
12.2
8.9
8.0
8.2
7.7
5.9
Mt. Simon Core No. 15 3148.0 - 3178.0
34
-------
DURING WELL CONSTRUCTION
AND DRILLING
Formation Fluids
Samples of water from subsurface formations can be obtained from
deep wells before they are completed, from cores, by formation test-
ing devices, and by swabbing.
When cores are taken, as previously described, the water in the cores
can be carefully extracted and its chemistry analyzed. Contamination is
a serious problem, since the core has been exposed to infiltration by
drilling mud and mud filtrate.
Drill-stem testing is a technique whereby a zone in an open borehole
can be isolated by an expandable packer or packers and fluid from the
formation allowed to flow through a valve into the drill pipe.
The basic drill-stem test tool assembly consists of:
1. A rubber packing element or packer which can be expanded
against the hole to segregate the annular sections above
and below the element
2. A tester valve to (a) control flow into the drill pipe, that
is, to exclude mud during entry into the hole and to allow
formation fluids to enter during the test, and an equalizing
or bypass valve to (b) allow pressure equalization across
the packer(s) after completion of the flow test.
Figure 20 illustrates the procedure for testing the bottom section of a
hole. While going in the hole, the packer is collapsed, allowing the dis-
placed mud to rise as shown by the arrows. After the pipe reaches bottom
and the necessary surface preparations have been made, the packer is set
(compressed and expanded); this isolates the lower zone from the rest of
the open hole. The compressive load is furnished by a slacking off of
the desired amount of drill-string weight, which is transferred to the
anchor pipe below the packer.
The tester valve is then opened and thus the isolated section is ex-
posed to the low pressure inside the empty, or nearly empty, drill pipe.
Formation fluids can then enter the pipe, as shown in the second picture.
At the end of the test, the tester valve is closed, trapping any fluid above
it, and the bypass valve is opened to equalize the pressure across the
packer. Finally, the setting weight is taken off and the packer is pulled
free. The pipe is then pulled from the hole until the fluid-containing
section reaches the surface. As each successive pipe section is removed,
its fluid content may be examined.
Although the above is a very common type of test, there are many other
variations of procedure, as indicated in Figure 21. The straddle packer
35
-------
ACQUISITION OF SUBSURFACE DATA
PERFORATED
ANCHOR PIPE
GONGN
REVERSING
Figure 20. Fluid passage diagram for a conventional bottom
section, drill stem test (Gatlin, 1960).
36
-------
DURING WELL CONSTRUCtlON
AND DRILLING
GENERAL PROCEDURE
(A) STRADDLE PACKER
TEST
IB) CONE PACKER TEST
(C) WALL OVER CONE
PACKER TEST
(D) TESTING THROUGH
PERFORATIONS IN
THE CASINO
Figure 21. Schematic illustration of various drill stem test
conditions (Kirkpatrick, 1954).
test is necessary when isolation from formations both above and below the
test zone is necessary. Such a situation commonly arises when it is de-
sired to test a zone previously passed by. Straddle testing is less desir-
able than conventional testing, from both a cost and an operational hazard
standpoint. Two packers are more apt to become stuck than one, since
any material which sloughs or caves from the test zone may accumulate
between the packers. Also, two positive, pressure-tight packer-formation
seals are required for a successful test. Consequently this procedure is
not preferred, and is applied only when necessary. This should not be
construed to mean that these disadvantages prevent one from making such
tests but rather that the additional problems the tests entail should be
recognized.
Formation testing devices are available which can be lowered into the
borehole on a wire line. In this case, the sample is limited to the amount
that can be contained in the testing device (up to about 5 gallons).
Swabbing is a method of producing fluid that is similar to pumping a
well. In swabbing, fluid is lifted from the borehole through drill pipe,
casing, or tubing by a swab that falls freely downward through the pipe
and its contained fluid, but which seats against the pipe walls on the up-
stroke, drawing a volume of fluid above it as it is raised. Swabbing may
be used in conjunction with drill-stem testing to increase the volume of
37
-------
ACQUISITION OF SUBSURFACE DATA
fluid obtained. The advantage of swabbing is that it can be continued until
all drilling mud has been drawn from the pipe and the formation and the
chemistry of the water obtained reaches a steady state. This procedure
helps to insure that a representative sample of formation water is obtained.
Borehole Geophysical Logs
After a well has been drilled, a variety of borehole logging tools are
available that can be used to produce a record of the nature of the forma-
tions penetrated and their contained fluids. In borehole logging, a probe
is lowered into a well at the end of a wire cable and selected geophysical
properties are measured and recorded at the surface as a function of depth.
Current methods of well logging are too numerous to discuss in detail
here. A broad classification of the more commonly used methods is
shown in Table 5, together with their main applications. Because the
variety of available logging methods is so great, the suite used in logging
a well must be carefully selected to provide the desired information at
an acceptable cost. Local practice in the particular geographic area is
a valuable guide, since it represents the cumulative experience obtained
from logging many wells. Some of the objectives in logging injection
wells will generally be: determination of lithology; bed thickness; amount,
location and type of porosity; and salinity of formation water. In order
to achieve these objectives, a commonly chosen suite of logs will include
a gamma ray log, a focused resistivity log, and one or more porosity
measuring logs selected from among the various radiation and elastic
7a!e !°,gc^ STe °ther fre
-------
DURING WELL CONSTRUCTION
AND DRILLING
Table 5. Well logging methods and their applications (modified after Jennings
and Timur, 1973).
Method
Property
Application
01
M
y 3
h- <
ui §=
Spontaneous
Potential (SP)
Nonfocused
Electric Log
Focused
Conductivity Log
Focused
Resistivity Logs
Focused and
Nonfocused
Microresistivity Logs
Transmission
Reflection
Electrochemical and
electrokinetic potentials
Resistivity
Resistivity
Resistivity
Resistivity
Compressional and
shear wave velocities
Compressional and
wave attenuations
Amplitude of reflected
waves
Formation water resistivity
(Ry/); shales and nonshales;
bed thickness; shaliness
a. Water and gas/oil satura-
tion
b. Porosity of water zones
c. Rw in zones of known
porosity
d. True resistivity of for-
mation (Rf)
e. Resistivity of invaded
zone
a, b, c, d
Very good for estimating Rj.
in either freshwater or oil
base mud
a,b,c7d
Especially good for deter-
mining fy of thin beds
Depth of invasion
Resistivity of the flushed
zone (RXO) for calculating
porosity
Bed thickness
••^••••«•
Porosity; lithology; elastic
properties, bulk and pore
compressibilities
Location of fractures;
cement bond quality
Location of vugs, fractures;
orientation of fractures and
bed boundaries; casing
inspection
(continued)
39
-------
ACQUISITION OF SUBSURFACE DATA
Table 5 — Continued
Method
Property
Application
O
§
a
2
Gamma Ray
Spectral
Gamma Ray
Gamma-Gamma
Neutron-Gamma
Neutron-Thermal
Neutron
Neutron»sEpithermal
Neutron
Pulsed Neutron
Capture
Spectral Neutron
Natural radioactivity
Natural radioactivity
Bulk density
Hydrogen content
Hydrogen content
Hydrogen content
Decay rate of thermal
neutrons
Induced gamma ray
spectra
Shales and nonshales; shall-
ness
Lithologic identification
Porosity, lithology
Porosity
Porosity; gas from liquid
Porosity; gas from liquid
Water and gas/oil satura-
tions; reevaluation of old
wells
Location of hydrocarbons;
lithology
IU
x
Caliper
Dipmeter
Deviation Log
Gravity Meter
Ultra-Long Spaced
Electric Log
Nuclear Magnetism
Production or
Injectivity
Temperature Log
Borehole diameter
Azimuth and inclination
of bedding planes
Azimuth and inclination
of borehole
Density
Resistivity
Amount of free hydro-
gen; relaxation rate of
hydrogen
Temperature, flow rate,
fluid specific gravity,
pressure
Temperature
Calculation of cement vol-
ume; location of mud cake
Dip and strike of beds
Borehole position
Formation density
Salt flank location
Effective porosity and per-
meability of sands; porosity
for carbonates
Downhole production or
injection
Formation temperature
40
-------
DURING WELL CONSTRUCTION
AND DRILLING
100 ohm-m
Figure 22. Portion of a Later log-gamma ray-neutron log from a
deep well in northern Illinois.
41
-------
ACQUISITION OF SUBSURFACE DATA
o
m
INTERVAL TRANSIT TIME
MICROSECONDS PER FOOT
Figure 23. Portion of a sonic log from a deep well in northern Illinois.
42
-------
DURING WELL CONSTRUCTION
AND DRILLING
2800
2900
3000
3100
Figure 24. Portion of a temperature log from a deep well in northern
Illinois.
43
-------
ACQUISITION OF SUBSURFACE DATA
the Laterlog (Figure 22), the resistivity of this interval is about 40 ohm-
meters. From the Archie equation (Schlumberger, 1972) the formation
factor F is 45 and the resistivity of the formation water is 0. 625 ohm-
meters. A sodium chloride water with a resistivity of 0. 625 ohm-meters
has a dissolved solids content of about 8, 000 ppm at 83. 5°F, Actually,
the formation water salinity is probably about twice the calculated value
because the Laterlog yields incorrectly high resistivities when run in
low-salinity mud, as is the case here. An induction log would yield more
accurate results in such a situation. This example illustrates some of
the principal uses of borehole geophysical logs in conjunction with the
evaluation of geological conditions in wastewater injection wells. Fur-
ther uses will be covered in Section VII, on well monitoring. Keys and
Brown (1973) give a more complete discussion of the application of bore-
hole geophysical logs to wastewater injection than is possible here.
Testing of Injection Units and Confining Beds
Examination of the records of many of the wastewater injection wells
that have been constructed up to the present time shows that, with few
exceptions, the maximum amount of usable geologic and engineering in-
formation has not been obtained during the testing of wastewater injection
wells. This is regrettable, because such tests provide the best basis for
analyzing reservoir conditions prior to injection, for predicting the long-
term behavior of the well and the reservoir, for detecting and understand-
ing changes in well performance that may occur during operation, and for
analyzing the history of a well from its records.
The methods for testing of pumping or injection wells and the techniques
for analysis of test data are discussed in numerous textbooks and in hun-
dreds of other publications concerning groundwater and petroleum engineer-
ing. Because the number of published articles and the scope of their con-
tent are so extensive, only a few selected references are mentioned and a
few examples discussed here to establish the reasons for and methods of
well testing.
A well can be tested by pumping from it or injecting into it. Measure-
ments of reservoir pressure or water level can be made during pumping
or injection or, alternatively, after pumping or injection has ceased and
the reservoir is adjusting to its original condition. Furthermore, reser-
voir pressure or water level can be measured in the principal well or in
adjacent observation wells. Any one of these approaches will yield much
of the same information.
44
-------
DURING WELL CONSTRUCTION
AND DRILLING
Drill Stem Test ing
In the case of the usual deep and rather expensive wastewater injection
well, there will be no observation well and testing will be in the well itself.
In the sequence of well construction and testing, the first type of formation
test that is likely to be made is the drill-stem test (DST). As has pre-
viously been mentioned* this test is analogous to a pumping test of lim-
ited duration. Quantitative analysis is usually made using data obtained
during the period of pressure buildup following the period in which the
reservoir is allowed to flow.
Figure 25a is a schematic DST pressure record, with a description of
the sequence of events in a successful test. Figure 25b is a schematic
representation of a test in which no fluid was produced. Conditions that
may be encountered in a DST are widely variable and considerable exper-
ience may be required in order to interpret an unusual test. The com-
panies that provide the testing services also provide assistance in test
interpretation.
If a test is successful, pressure buildup data from the test are taken
from the DST chart and tabulated. These data are then plotted as shown
in Figure 26. A series of calculations of formation properties are then
made. The properties that are routinely calculated and are of importance
here are:
1. Static bottom-hole pressure
2. Transmissivity
3. Average effective permeability
4. Damage ratio
5. Approximate radius of investigation.
The static bottom-hole pressure as determined from a successful test
is assumed to closely represent the formation pressure at the elevation
of the pressure recording device. Transmissivity is average permeability
multiplied by the thickness of the test interval. The damage ratio is an
indication of the amount of plugging of pores in the formation during drill-
ing of the well. In addition to this routine information, drill-stem tests
may indicate the presence of and distance to nearby faults or facies changes
that act as barriers to flow or channels for rapid flow.
For detailed presentations of drill-stem test analysis, the reader is
referred to Gatlin (I960),. Lynch (1962), Matthews and Russell (1967) and
Pirson (1963). Also, literature such as that by Murphy (undated) is read-
ily available from companies that provide drill-stem testing services.
45
-------
ACQUISITION OF SUBSURFACE DATA
Timt —•>
X Putting water cushion in drill pipe
2 Running in hole
Hydrostatic pressure (weight of mud column)
Squeese created by setting packer
Opened tester, releasing pressure below packer
Flow period, test cone producing into drill pipe
Shut in pressure, tester closed immediately above packer
Equalising hydrostatic pressure below packer
Released packer
Pulling out of hole
Figure 25a. Normal sequence of events as recorded on the chart
during a successful drill-stem test (Kirkpatrick, 1954).
t
Time —»•
1. Running in hole
2. Hydrostatic pressure (weight of mud column)
3. Squeese created by setting packer
4. Opened tester, releasing pressure below packer
5. Flow period, test cone open to atmosphere
Closed tester and equalizing hyd, pressure below packer
Pulled packer loose
Pulling out of hole
6.
7.
8.
Figure 25b. Sequence of events as recorded during a drill-stem
test when no fluids were produced (Kirkpatrick, 1954).
46
-------
STATIC BOTTOM HOLE PRESSURE - f!
•0.
- 1160.
- 1140.
•5
- 1100.
1080.
1060.
O
2
Z
o
n
>O
zz
Figure 26. Example of a plot of data from a drill-stem test with dual closed-in periods (Murphy, undated).
oz
-------
ACQUISITION OF SUBSURFACE DATA
As an example of DST analysis, data from testing of the Mt. Simon
Formation in a well in Ohio were selected. Figure 27 is a plot of the
pressure buildup data for that test. Extrapolation of the data to the
logarithm of (t + 6)/6 = 0 shows that the static formation pressure is
2750 psig. The gage was at a depth of 5886 feet in the well, so the fluid
pressure gradient is 0.467 psi per foot of depth.
For the remaining calculations, the following values from the test
are needed (dimensionalized in oil field units):
Pf = final flow pressure = 1061 psig
t = final flow time = 62 min
m = PS " PlO = l63 psi per log cycle
Q = average flow rate = 347 bbls/day
jj = water viscosity = 1.065 centipoise
b = formation thickness = 105 ft.
Then,
T = transmissivity = 162.6— (millidarcy-ft/centipoise) (9)
m
_
K = average permeability = -rp- (millidarcys) (10)
0. 183(Pfl - Pf)
DR = damage ratio = - (dimensionless) (11)
— 1/2
r = radius of investigation 2= (Kt) . (12)
The transmissivity is computed to be 345 millidarcy-ft/centipoise, the
average permeability 3.5 millidarcys, the damage ratio 1.9, and the ra-
dius of investigation 14. 73 ft. These calculations reveal that the Mt.
Simon Formation at this location has a very low capacity to accept in-
jected fluids. The capacity could theoretically be improved nearly 100
percent by removing formation damage; reservoir stimulation by hydrau-
lic fracturing would also help, but the reservoir is not promising. No
hydrologic boundaries were encountered within the radius of investigation*
which was only about 14 feet. Further well testing and core analysis re-
sults to confirm these findings are discussed in the material that follows.
48
-------
DURING WELL CONSTRUCTION
AND DRILLING
2550
2600
Q.
1 2650
UJ
QJ 2700
tc
Q.
Ill
§ 2750
O
2800 -
_L
_L
_L
~OJ O2 OS O4
LOGARITHM OF t
0.5
0.6
0.7
0.8
Figure 27. Plot of extrapolated pressure from drill-stem test data from an
injection well in Ohio.
Injectivity Tests
After an injection well has been drilled and possible injection intervals
identified by coring, by geophysical logging, and by drill-stem testing,
injection tests will usually be run. For initial injection testing, truck-
mounted pumps are often rented and treated water used for injection
rather than wastewater. Frequently, more than one possible injection
interval is present and tests are performed on the intervals individually
or on more than one at a time. The common practice when performing
an injection test is to begin injection at a fraction of the final estimated
rate, to inject at this rate for at least several hours, then to repeat this
process at increasingly greater rates until a limiting rate or pressure
is reached. Injection is then stopped and the reservoir allowed to return
to its original pressure state. Pressures may or may not be recorded
during this fall-off period.
Regardless of the sequence in which a test is performed, if pressure,
time, and flow data are accurately recorded, and the test is run long
enough, it is theoretically possible to analyze the test. However, the
simpler the test the simpler and probably more reliable the interpretation.
Tests performed on more than one interval at a time are particularly
difficult to interpret and should be avoided if possible or, alternatively,
both single and multiple zone tests performed.
49
-------
ACQUISITION OF SUBSURFACE DATA
Figure 28 is a plot of the data from a constant.-rate injectivity test of
the Mt. Simon Formation. The test was run at 75 gpm for about 25 hours,
The equation used to determine formation transmissivity from Figure Z»
is:
(13)
Alternatively, Equation 9 can be used. Any consistent units can be used
in Equation 13, whereas Equation 9 is dimensionalized for oil field units
as previously indicated.
Using Equation 9
162.6 X 2571bbl/day =
x 925 psi/log cycle
Using Equation 13
7. ^n x
T =
millidarcy.ft/centipoise .
or
4ff X2136 ft/log cycle
T = 9.3 gal/day ft .
ISOOl
• 925 pit
THIS PORTION OF CURVE
NOT USABLE FOR ANALYSIS
\
O.I I. I 10
TIME - HOURS
Figure 28. Plot- of pressure buildup data from an injectivity test of the
Mt. Simon Formation in Ohio.
50
-------
DURING WELL CONSTRUCTION
AND DRILLING
This test was run on the same well for which the drill-stem test analy-
sis was given, but the well bore was cleaned up and acidized before the
injectivity test, thus leading to a slightly higher transmissivity.
The injectivity test can further be used to determine the formation stor-
age coefficient from
2.25Tt
s = - — 9. (dimensionless)
where to = intercept of extrapolated test curve with time axis
r = radius of well bore.
In Figure 28, to = 2.2 hours and
_ 2. 25 X 1. 24 ft2/day X 0. 0092 days _ 0. 16
(0. 396)2
As was previously discussed, storage coefficient values for confined
aquifers are generally at least three orders of magnitude lower than the
calculated value^of 0. 16. As a better estimate, Equation 7 (page 27)
yields a value for the storage coefficient of 3. 34 X 10~4. It is believed
that the discrepancy in this case results from the fact that the well was
hydraulically fractured during an earlier injection test, leading to a
greatly enlarged effective well bore. As an estimate of the degree of
enlargement, Equation 14 is rearranged and solved for r , using the cal-
culated storage coefficient, yielding:
1. 25 Tt
o
. /
= \/
v
2. 25 X 1. 24 ft^/day X 0. 009 days = g> ? ft
-4-
3. 34 X 10 *
This is a reasonable value and will be used in later calculations.
If early time data are available, an alternative form of analysis that
involves curve matching can be employed. Figure 29 is such a plot of
recovery data for an injection well at Mulberry, Florida. The details
of the analysis of this test are given by Wilson et al. (1973). The most
interesting aspect of this example is that the test data indicate an observ-
able amount of leakage through the confining beds. Witherspoon and
Neumann (1972) discuss in some detail the theory and procedure for anal-
ysis of leaky confining beds and give two field examples from gas storage
projects
51
-------
ACQUISITION OF SUBSURFACE DATA
100
j
*
10
I I
I I
I 1 I TT I I
TRACE OF THEIS NON-LEAKY
Italch
A WU,5»)»I
J^.I
WM'
ARTESIAN r/B - 0.01 TYPE CURVE
I
I
I 1 I I I
10
100 1000
TIME SINCE INJECTION STOPPED. mimiM
10.000
Figure 29. Plot of recovery data and matching-type curves for an injection
test of a well at Mulberry, Florida (Wilson et al., 1973).
Readers wishing to pursue the subject of aquifer testing further are
referred to the same references previously given for drill-stem test
analysis, particularly to the Society of Petroleum Engineers Monograph
prepared by Matthews and Russell (1967). Additionally, publications in
the groundwater field by Lohman (1972) and Kruseman and De Ridder
(1970) are excellent recent summaries of this subject, as is the refer-
ence by Witherspoon et al. (1967), which was prepared for the underground
gas storage industry.
52
-------
SECTION VI
PREDICTION OF AQUIFER RESPONSE
FLOW THEORY
The basic equation used to describe the flow of fluids in porous media
is Darcy's law, alternate forms of which are given on page 25 by Equa-
tions 3, 4, and 5. Darcy's law alone can be used for calculations of
steady flow. Steady flow occurs when the same quantity of fluid is en-
tering an aquifer as is leaving it, so that no change in volume of the aqui-
fer or its contained fluid is occurring with time.
When flow is unsteady or, as stated in oil field terminology, when for-
mation pressures are transient, Darcy's law must be combined with the
continuity equation so that time and the compressibility of the aquifer and
aquifer fluids may be taken into account. The appropriate partial differ-
ential equation and its derivation may be found in most modern texts on
hydrogeology and petroleum reservoir engineering, along with numerous
solutions.
The solution first formulated and still most widely used is that for a
well pumping from or injecting into an aquifer under the following conditions!
1. The aquifer is, for practical purposes, infinite in areal
extent
2. The aquifer is homogeneous, isotropic, and of uniform
thickness over the area of influence
3. Natural flow in the aquifer is at a negligible rate
4. The aquifer is sufficiently confined so that flow across
confining beds is negligible
5. The well penetrates the entire thickness of the aquifer
6. The well is small enough that storage in the well can be
neglected and water removed from storage in the aquifer
is discharged instantaneously.
This is a formidable list of assumptions, which are obviously not com-
pletely met in any real situation. However, if one reviews the character-
istics of aquifers such as the Mt. Simon Formation, it can be concluded
53
-------
PREDICTION OF AQUIFER RESPONSE
that they probably comply with the assumptions sufficiently for practical
purposes.
The equation that describes the response of such an aquifer to a single
injection well is then:
_J2
where
r*S
U = 4Tt (dimensionless)
and Ah = hydraulic head change at radius r and time t
Q = injection rate
T = transmissivity
S = storage coefficient
t = time since injection began
r = radial distance from well bore to point of interest.
One can easily enter the desired values into this series solution, or
tables with the series evaluated are available in the previously referenced
publications on aquifer testing.
For large values of time, small values of radius of investigation, or
both, Equation 15 can be reduced to:
2. 25Tt
r2S
Equations 15 and 16 are not dimensionalized; therefore, any consistent
units can be used.
Two very important characteristics of the equations presented above
are that individual solutions can be superimposed, and that hydrologic
boundaries such as faults can be simulated by a properly located imagi-
nary well The fact that solutions can be superimpoWallowsfheTffects
of multiple wells to be easily analyzed. Because the effect of boundaries
is analogous to that of properly located pumping or injection wells the
existence of boundaries can be detected by observing aquifer response to
injection or pumping or, conversely, the effects of known or suspected
boundaries can be estimated.
54
-------
REGIONAL FLOW
REGIONAL FLOW
As examples of the application of Darcy's law to analysis of regional
flow, the velocity of natural flow in the Mt. Simon Formation in Ohio and
the lower Floridan aquifer in Florida will be considered.
From Figure 18 (page 30) it can be seen that, at the location of the
Empire-Reeves injection well, the hydraulic gradient is 8 feet per mile
toward the northwest. At this location, the Mt. Simon Formation has a
permeability of 24 millidarcys (from a drill-stem test) and a porosity
of 10.4 percent (Clifford, 1973). Rearranging Darcy's law:
- = . K (L/T)
A aJL
where v = apparent velocity through entire area A.
Then,
v _Q. K dh (18)
v = 0 = A0 = 0
where v = average velocity of flow through pores
0 = porosity.
From the data given above, converted to consistent units, and entered
into Equation 18
v =
21.3639 ft/yr y 8 ft/mile
y
o. 104 5,280 ft/mile
= 0.31 ft/yr .
This evaluation shows that water in the Mt. Simon Formation in north-
central Ohio is moving northwest at a rate of 0. 31 ft/yr. The a°*rce °f
the hydraulic gradient and the fate of the moving water are not understood.
Furth'ermore^there are complications in the analysis itself, as poxnted
out by Bond (1973). However, in spite of such uncertainties, it can be
injection site.
55
-------
30»30'
•7*30'
EASTERN LIMIT-
BUCATUNNA CLAY
CONFINING BEOS
JP°}0'
6UI-F
of
CO
IZ HUES
Contour shows oiiitudc of inferred _____ Areo where soiine woter from lower
potentiometric surfoce of the lower ~ Fioritfon oquifer moves upward and
limestone ooove mean sea level, pre- mixes with fresh water m upper Fioridon
1963. Contour interval. 20 feet. aquifer under natural conditions.
_——looo isochlor shows inferred chloride °l Fault, dashed where inferred
concentration (milligrams per liter) ;
within upper port of the lower limestone
1 1
O
n
O
O
•n
I
m
70
to
•u
O
•7.
CO
m
Figure 30. Hydrogeology of the lower Floridan aquifer in northwest Florida (Goolsby, 1972).
-------
PRESSURE EFFECTS OF INJECTION
The permeability is about one darcy and the porosity is estimated to be
10 percent (Goolsby, 1971 and 1972). The velocity of natural flow in the
lower Floridan aquifer is then estimated to be
v _ 890 ft/yr 1.33 ft/mile _
v - 0>10 X 5,280 ft/mile - Z'24 ft/yr '
This analysis is more easily interpreted than the previous one for Ohio,
because it is well known that the source of hydraulic head lies to the north
of the injection well site and that the discharge area lies to the south as
shown in Figure 31. The velocity of flow is again very low; it appears
that more than 200, 000 years would be required for injected waste to
reach the subsea discharge point 100 miles to the south.
PRESSURE EFFECTS OF INJECTION
Wastewater injected into deep aquifers does not move into empty voids;
rather it displaces existing fluids, primarily saline water. The displace-
ment process requires exertion of some pressure, in excess of the natural
formation pressure. The pressure increase is greatest at the injection
well and decreases in approximately a logarithmic manner away from the
well. The amount of excess pressure required and the distance to which
it extends depend on the properties of the formation and the fluids, the
amount of fluid being injected, and the length of time that injection has
been going on. The pressure or head changes resulting from injection
are added to the original regional hydraulic gradients to obtain a new po-
tentiometric surface map that depicts the combined effects of regional
flow and the local disturbances.
By use of the theory that has been described, potentiometric surface
maps can be produced to show the anticipated situation at any time in the
future. If observation wells exist, the actual potentiometric surface at
any time can be constructed from the water levels or pressures recorded
in the wells.
Figure 32 shows the theoretical potentiometric surface map for the
lower Floridan aquifer in northwestern Florida in 1971, after wastewater
injection had been in progress near Pensacola for about eight years. The
estimated pressure effects of injection can be seen by comparing Figure 30
with Figure 32. The comparison indicates that changes in hydraulic head
may extend out for 30 miles or more from the injection site. Although
Figure 32 is titled a theoretical potentiometric surface map, it is, in
fact, partially substantiated by observation wells. If more observation
wells were available, the map would be constructed entirely from observed
data.
57
-------
500*
SEA
LEVEL
LOCATION MAP
ABOUT 100 MILES TO DISCHARGE AREA »-j-«-ABOuT 75 MILES TO RECHARGE AREA
BOO
2000
2500'
3000
3500*
O
n
6
§
>
D
Tl
m
3
Figure 31. Generalized north-south geologic section through southern Alabama and northwestern Florida
(Goolsby, 1972).
-------
3i»OO _
SO»SO' -
EASTERN LIMIT.
BUCATUMNA CLAY
,r CONF1NINC BCD
Si'OO
-SO»X
12 MILES
Contour show oltitude of theoretical ~///t_ Areo where saline woler from lower
potentiometric «urfoce of the tower Fioridon aquifer moves upward and
limestone in feet above meon sea level,
lote 1971. Contour interval, 20 feet.
--- iboo Iscchlor shows inferred chloride
concentration (milliarams per liter)
within upper port of the lower limestone.
mixes with fresh water m upper Fioridon
aquifer under natural conditions.
MU c •. ^ t ^ _^ • .
T Fou" • dothed «**rt inf«"««»-
m
CO
CO
m
•n
-n
CO
o
Figure 32. Theoretical potentiometric surface of lower limestone of F lor I dan aquifer in late 1971 (Goolsby, 1972).
O
-------
PREDICTION OF AQUIFER RESPONSE
As an example of the development of such a theoretical potentiometric
surface map, one point on Figure 32 will be determined. The point will
be one at a radial distance of 6 miles northeast of the injection well site,
which places it at a potential of about 77 feet on Figure 30 and 180 feet on
Figure 32, showing a head increase of about 103 feet. From Goolsby (19?Z)»
the following data were obtained or estimated:
Q = 2.427 X 106 gal/day = 3. 244 X 105 ft3 /day
T = 6,300 gal/day ft = 842 ft3/day ft
t =3, 000 days
r = 6 miles = 31,680 ft
S = 2 X 10"4 (dimensionless) .
Therefore, from Equation 16, the head increase in 3,000 days 6 miles
northeast of the injection site is:
Ah = 2.30X 3.244 X IQ5 ft3/dav
4ff x 842 ft3 /day -ft
X inC 2'25 X 842 ft3/day-ft X 3,000 days
(31,680ft)2 X 2 x 10"4
= 70.50 log 28.31 = 102.4ft .
The calculated increase of 102. 4 feet compares very well with the 103
feet obtained from Goolsby's maps. As many points as desired can be
I - Pfr,°d*CMhe contour «**• Rather than calculating the pres-
° aCU °n a CirClC Wi*h radius r > even hea* increments
radii to
, and for which a
e **" ™° P"«nted, will also be used as
t dr^re, .a yiC,lded * tranami"^ty of 954 millidarcy-ft/
Si vfem t6/* 345 ^^a^y-ft/centipoise, and the in-
4"dimhllldarcy:ft/c^ipoise.. The value from the injection
asrr.-a: ? s
60
-------
PRESSURE EFFECTS OF INJECTION
i * 4ff T Ah log 2.25T
10* * = T30Q - 2q
r o
. A (4ff) (1.24 ft2/day) (4157ft) (2.25) (1.24 ft2/day)
log t = J—u "-4 - log ^r ^4
(2. 30) (14,437 ft3/day) (8. 7 ft)* (3. 34 X 10 )
log t = 1.95 - log 110.36 = -0.092
t= 0. 81 days = 19.4 hours.
This value could also have been obtained by extrapolating to 1800 psi the
line in Figure 28 (page 50), but only for the same injection rate and radius
of investigation and not for other rates and radii.
As the injection rate is changed the amount of time required for the
pressure to increase to a particular level changes proportionately, so
that for an injection rate of 50 gpm, t = 27 hours, and for an injection
rate of 25 gpm, t = 54 hours.
For this well, the calculations simply confirm what could already have
been intuitively deduced; the fact that the Mt. Simon Formation will not
be a suitable injection unit at this location. Similar calculations could
have been made from core data and from the drill-stem test and this con-
clusion reached prior to injection testing.
In comparison with the Ohio example, a well in northern Illinois had
the following characteristics:
b = 1734 ft
K =36 millidarcys
av.
T = 62.42 darcy'ft
Q = 100 gpm
rwell = 4-4in'
S = 5.46 X 10'3 .
Using these data, what will be the injection pressure increase at the
well after 5 years of continuous operation?
lf F2.30 X 19. 248 ft3/day
Ap = 0.433 psi/ft — "
4ff x 167 ft2/day
2.25 X 1825 days X 167 ft2/day
X log o ^3
(0.36 ft) x 5.46 X 10
= 81 psi
61
-------
PREDICTION OF AQUIFER RESPONSE
This calculation shows that the pressure increase will be negligible.
In actual operation, the injection pressure has averaged 120 to 300 psi;
the difference between predicted and observed performance is not of
concern in this case unless the observed pressure continues to increase,
indicating possible progressive plugging of the formation.
Multiple Wells
As previously mentioned, estimating the combined pressure effects
of multiple wells is made easy by virtue of the principle of superposition.
It is only necessary to estimate the separate effects of two or more wells
at the point of interest, then to add them to obtain their combined effect.
For example, referring to the last Mt. Simon well discussed above, what
would the combined effects of two wells spaced 1,000 feet apart be on
each other after 5 years? Assume both wells have the same character-
istics:
Ap = 81 psi + 0.433 psi/ft I"2'30* 19, 248 ft3/day
L 47T X 167 ft2/day
X log 2'25 * 1825 x I67ft2/dav1
(1000ft)2 x 5.46 x 10"3 J
Ap = 81 psi + 19 psi = 99 psi .
Hydro logic Discontinuities
Another common situation is one in which a barrier to flow a fault or
facies change, is present within the area of influence of an injection well.
Faults may also act as channels for escape of fluid from the injection
horizon.
In predicting aquifer response in the presence of such features, the
image-well concept is used. Assume the presence of a fault or lithologic
change that acts as an impermeable barrier, 500 feet in any direction
from the Mt. Simon Formation injection well that is discussed above
Then according to image-well theory, an imaginary injection well with
all of the same properties as the real injection well is placed 1,000 feet
from the real well, on the opposite side of the fault and on a line that
passes through the real well and is perpendicular to the fault. Figure 33
shows the potentiometric surface and flow lines that would develop in such
a situation; the pressure effect of the barrier would be the same as that
calculated above for an actual injection well 1, 000 feet from the first well.
If the hydrologic discontinuity were a leaky fault rather than a sealed
one, the opposite effect would occur; the pressure at any time would be
reduced as if a discharging well were present.
62
-------
Figure 33. Generalized flow net showing the potential lines and stream lines in the vicinity of an
injection well near an impermeable boundary (Ferris et al., 1962).
CO
CO
73
m
m
n
CO
O
z
c_
rn
O
-------
PREDICTION OF AQUIFER RESPONSE
The equations and examples given are for the most basic hydrogeologic
circumstances, but many injection wells can be treated this way because
these are the conditions sought when choosing an injection site and re-
ceiving aquifer. However, cases of virtually any complexity can be ana-
lyzed by use of the appropriate solution to the basic flow equations; where
analytical solutions are not possible, numerical models can be developed.
The limitations to an analysis are usually pragmatic rather than theoretical
-lack of data, limitations of time and funds, or the fact that a simplified
estimate is sufficient for the circumstances.
RATE AND DIRECTION OF FLUID MOVEMENT
As with pressure response to injection, the rate and direction of move-
ment of the injected fluid depend on the hydrogeology of the site; therefore,
the same factors previously listed require consideration. In addition, the
properties of the formation water and the injected wastewater assume major
importance.
Broad flow patterns in an aquifer with a significant existing potentio-
metric gradient can be deduced from a map of the regional potentiometric
surface with the effects of the injection system superimposed.
Figure 34 is a duplication of Figure 32, with flow lines added to show
how the flow directions of aquifer water and injected wastewater can be
deduced from the potentiometric surface map. The wastewater will never
actually travel as far northward as the map indicates, but displaced aquifer
water will be forced in this direction, ahead of the small cylinder of waste-
water that surrounds the well. The extent of this wastewater cylinder will
be discussed next.
A good estimate of the minimum distance of wastewater flow from an
injection well can be made by assuming that the wastewater will uniformly
occupy an expanding cylinder with the well at the center. The eauation
for this case is: H
r = (19)
where r = radial distance of wastewater front from well
V = Qt = cumulative volume of injected wastewater
b = effective aquifer thickness
0 = average effective porosity.
64
-------
3i •00'
ALABAMA
•-x«P ( INJECTION SITE.
EASTERN LIMIT.
aUCATUNNA CLAY
CONFINING KO
EXPLANATION
12 MILES
1000
Contour shows oltitude of theoretical
potentiometric surface of the tower
limestone in feet above mean sea level.
tote 1971. Contour interval, 20 feet.
Iscchlor shows inferred chloride
concentration (milligram* per liter)
within upper port of the lower limestone.
Area where saline water from lower
Fioridon aquifer moves upward and
mixes with fresh water in upper Fioridon
aquifer under natural conditions.
Fault, dashed where inferred.
JO»JC
Si
Figure 34. Theoretical potentiometric surface of lower limestone of Floridan aquifer in fate 1971, with flow lines show-
ing the directions of aquifer water and wastewater movement. Solid flow lines show the direction of flow of
diverted aquifer water, dashed flow lines show direction of flow of injected wastewater and displaced aquifer
water (modified after Goolsby, 1972). H
^W. • ••
m O
SO
-------
PREDICTION OF AQUIFER RESPONSE
For a Mt. Simon injection well with the following characteristics:
Q = 100 gpm
t = 5 years
b = 1618 feet
0 = 13.5 percent
35,128,993 ft3
X 1618 ft X 0. 135
= 226 ft ,
It is noted that effective aquifer thickness and average effective porosity
should be used. The effective aquifer thickness is, for example, that part
of the total aquifer that consists of sandstone in the case of a mixed
sandstone-shale lithology. The effective porosity has been previously
defined as that part of the porosity in which the pores are interconnected.
In most situations the minimum radial distance of travel will be ex-
ceeded, because of dispersion, density segregation, and channeling through
high permeability zones. Flow may also be in a preferred direction, rather
than radial, because of hydrologic discontinuities (e.g., faults), selectively
oriented permeability paths, or natural flow gradients.
An estimate of the influence of dispersion can be made with the follow-
ing equation:
r' = r + 2.3/Dr" (L) (20)
where r' = radial distance of travel with dispersion
O = dispersion coefficient; 3 ft for sandstone aquifers and
65 feet for limestone or dolomite aquifers.
Equation 20 is obtained by solving equation (10.6.65) of Bear (1972)
for the radial distance at which the injection front has a chemical concen-
tration of 0. 2 percent of the injected fluid.
The detailed development of dispersion theory is presented by Bear
(1972). The dispersion coefficients given are high values for sandstone
and limestone aquifers obtained from the literature. No actual dispersion
coefficients are known to have been obtained for any existing injection
well.
66
-------
RATE AND DIRECTION
OF FLUID MOVEMENT
Then, for the above example, which is a sandstone:
r' = 226 ft + 2. 3 /3ft X 226 ft
= 286 ft .
It is clear that, in this example, the distance of wastewater travel
from the well is negligible and could not possibly be of concern if actual
conditions comply even generally with those that were assumed. This
conclusion has been found to apply to many of the wells that have been
constructed to date. Since almost no attempts have been made to deter-
mine the actual wastewater distribution around existing injection wells,
there is little evidence for comparison with theory. However, if such
a calculation were in error by several hundred percent, there would still
be no cause for concern, since the injection well, in this and many other
cases, is tens of miles from the nearest other well penetrating the injec-
tion zone.
To proceed beyond the calculations that have been shown may not be
necessary or, in many cases, meaningful. However, it may be possible,
if necessary, to account for some of the additional complications that
are mentioned. For example, Bear and Jacobs (1964), in one of a series
of reports, considered the flow of water from a groundwater recharge
well in an aquifer of uniform flow, when the densities and viscosities of
the injected and interstitial fluids are the same. Gelhar and others (1972)
developed analytical techniques for describing the mixing of injected and
interstitial waters of different densities.
So far, the travel of the injected wastewater has been treated as though
it were an inert fluid and would not react with the aquifer water or minerals,
be affected by bacterial action, or decompose or radioactlvely decay. If
the wastewater is not inert, then changes in chemical composition with
time and distance may also need to be considered. Bredehoeft and Finder
(1972) discuss the methodology for a unified approach to this type of prob-
lem and Robertson and Barraclough (1973) presented an example of a case
in which radioactive decay, dispersion, and reversible sorption were con-
sidered. However, no procedure exists at this time for simultaneously
considering the full range of practical possibilities that may be involved
in wastewater movement.
In spite of the degree of sophistication used in development of theories
for rate and direction of travel of injected fluid from an injection well,
nonuniform distribution of porosity and permeability will preclude making
accurate estimates in many cases. In general, wastewater flow in unfrac-
tured sand or sandstone aquifers would be expected to more closely agree
67
-------
PREDICTION OF AQUIFER RESPONSE
with theory than flow in fractured reservoirs or in carbonate aquifers
with solution permeability. However, even in sand aquifers, flow can
be expected to be non-ideal as shown by tests reported by Brown and
Silvey (1973). Particularly great deviations from predictions may occur
in limestone or dolomite aquifers. Figure 35 is an example of this. The
radial zones around Well No. 1 show the predicted extent of waste travel
using Equations 19 and 20. The irregular boundary shows the probable
actual extent of wastewater spread as indicated by evidence from Wells 2
and 3. In this case, the wastewater apparently traveled selectively in a
single thin porous and permeable interval rather than throughout the sev-
eral zones indicated by testing results. Accurate prediction of the rate
and direction of movement in such a case may well be technically infeas-
ible even in the future because the amount of information needed will sel-
dom, if ever, be available.
HYDRAULIC FRACTURING tt f^ORO - Ffcf\
-------
HYDRAULIC FRACTURING
pf damage to well facilities and because of the uncertainty about where
the fractures and injected fluids are going as fractures continue to be
extended.
Figure 36 is a schematic diagram of bottom-hole pressure versus time
during hydraulic fracturing. Before injection begins, the pressure is that
of the formation fluid (po) and the column of fluid in the well bore. Pres-
sure is increased until fracturing occurs; then, as fluid continues to be
pumped into the well, the pressure stabilizes at pf, the flowing pressure,
during which the fractures continue to be extended. When injection is
ceased, and the well shut in, the pressure quickly stabilizes to a constant
value, the instantaneous shut-in pressure. This pressure is considered
to be equal to the least principal earth stress in the vicinity of the well.
In estimating the fluid pressure at which hydraulic fracturing will occur
one of two conditions is usually assumed:
1. That the least principal stress is less than the vertical
lithostatic stress caused by the rock column. In this
case fractures are assumed to be vertical.
2. That the vertical lithostatic stress is the least principal
stress. In this case fractures will be horizontal.
In the first case, the minimum bottom-hole pressure required to ini-
tiate a hydraulic fracture can be estimated from (Hubbert and Willis, 1972):
S + 2p ,
p. * Z 3 ° (F/LZ)
where pj = fracture initiation pressure
Sz = total lithostatic stress
P0 = formation fluid pressure.
The fracture gradient, that is, the injection pressure required per foot
of depth, can be estimated by entering representative unit values into
Equation 21. The unit values for Sz and po are, respectively, 1.0 and
0.46 psi/ft. This yields a Pi gradient of 0. 64 psi/ft as a minimum value
for initiation of hydraulic fractures. This situation implies a minimum
lateral earth stress. As the lateral stresses increase, the bottom-hole
fracture initiation pressure also increases up to a limiting value of 1. 0
pfli/ft. Actually, fracture pressures may exceed 1. 0 psi/ft when the rocks
have significant tensile strength and no inherent fractures that pass through
the well bore. In any particular case, injection tests can be run to deter-
mine what the actual fracture pressure is, then operating injection pres-
sures held below the instantaneous shut-in pressure. In the absence of any
-------
PREDICTION OF AQUIFER RESPONSE
ID
ft.
9000
2000
1000
0
FORMATION
BREAKDOWN
"7 J
/
A 3AND AB
I I r~ FRAC
/\^ed
/r
//
1
I
r
SAND 1
Y~ INCRE*
DEDTO \
FLUID y*r'~m
'/
— — — DOWN
mm mm mm mm mm 9UKfi
Jt>AD
SED
HOLE PRESSURE
WE PRESSURE
PUMPS OfF-7
"\
!
\2L
\
\
s
" » 10 » » U
TIME - MINUTES
Figure 36. Schematic diagram of pressure versus time during hydraulic
fracturing (Kehle, 1964).
specific data, arbitrary limitations of from 0. 5 to 1.0 psi per foot of depth
have been imposed on operating injection wells. Regional experience should
be used as a criterion in establishing an arbitrary limit, since regional tec-
tonic conditions and fluid pressure gradients dictate what a safe limit will be,
GENERATION OF EARTHQUAKES
As a matter of background, it is widely, but not universally, accepted
that a series of earthquakes that began in the Denver area in 1962 was
initiated by injection of wastewater into a well at the Rocky Mountain Ar-
senal. Since the association of seismic activity with wastewater injection
at Denver, apparently similar situations have been observed at Rangely,
Colorado, and Dale, New York. The former related to water injection
for secondary recovery of oil and the latter to disposal of brine from so-
lution mining of salt. On the other hand, there are presently about 160
operating industrial wastewater injection wells and tens of thousands of
oil field brine disposal wells that have apparently never caused any notice-
able seismic disturbance, so these three examples would have to be con-
sidered very rare.
70
-------
GENERATION OF EARTHQUAKES
It has been erroneously stated by many that the seismic events have
been stimulated by "lubrication" of a fault zone by injected fluids. What
has happened, if injection has been involved, is that the water pressure
on a fault plane has been increased, thus decreasing the friction on that
plane and allowing movement and consequent release of stored seismic
energy.
Based on this interpretation of the mechanism of earthquake triggering
by fluid injection, some of the conditions that would have to exist in order
to have such earthquakes would be:
1. A fault with forces acting to cause movement of the blocks
on either side of the fault plane, but which are being suc-
cessfully resisted by frictional forces.
2. An injection well that is constructed close enough, verti-
cally and horizontally, to the fault so that the fluid pressure
changes caused by injection will be transmitted to the fault
plane.
3. Injection at a sufficiently great rate and for a sufficiently
long time to increase fluid pressure on the fault plane to
the point that frictional forces resisting movement become
less than the forces tending to cause movement. At this
time, movement will occur and stored seismic energy will
be released. That is, an earthquake will occur.
As has been discussed earlier in the section on state of stress, rela-
tively little is known about stress distribution in the earth's crust and
even less is known about stress distribution along fault systems. In the
absence of this information, only qualitative estimates of the probability
of earthquake stimulation can be made. In the great majority of cases
the potential for earthquake stimulation will be nonexistent or negligible
because only very limited areas in the country are susceptible to earth-
quake occurrence. The susceptible areas are delineated by records of
earthquakes that have occurred in the past and by tectonic maps that show
geologic features which are associated with belts of actual or potential
earthquake activity.
In a case where subsurface stresses are known or are determined by
hydraulic fracturing or other means, and where the location and orienta-
tion of the fault plane are known, then a quantitative estimate of the pres-
sure required to cause fault movement can be made. Raleigh (1972) pro-
vides an example of such a calculation from the Rangely, Colorado, oil
field.
71
-------
SECTION VII
SURVEILLANCE OF OPERATING WELLS
INJECTION WELL MONITORING
The principal means of surveillance of wastewater injection that is
presently practiced is monitoring at the injection well of the volume,
chemistry, and biology of the injected wastewater and of the well-head
and annulus pressures (Figure 37). To some this apparently seems in-
adequate. However, if all of the necessary evaluations have been made
during the planning, construction, and testing of the well, then this may
be a satisfactory program when combined with periodic inspection of
surface and subsurface facilities. This is because, as pointed out by
Talbot (197Z), the greatest risk of escape of injected fluids is normally
through the injection well itself, rather than from leakage through per-
meable confining beds, fractures, or unplugged wells.
The purpose of monitoring the volume of injected wastewater is to
allow for estimates of the distance of wastewater travel, to allow for
interpretation of pressure data, and to provide a permanent record of
the volume of emplaced wastewater. Also, a record is needed as evi-
dence of compliance with restrictions, for interpretation of well behavior,
and as a precaution in the event that a chemical parameter should deviate
from design specifications, Some characteristics that have been moni-
tored continuously are suspended solids, pH, conductance, temperature,
density, dissolved oxygen, and chlorine residual. Complete chemical
analyses are frequently made on a periodic basis on composite or grab
samples. Because bacteria may have a damaging effect on reservoir
permeability, periodic biological analysis of some wastewaters may be
desirable to insure that organisms are not being introduced.
Injection pressure is monitored to provide a record of reservoir per-
formance and as evidence of compliance with regulatory restrictions.
Injection pressures are limited to prevent hydraulic fracturing of the
injection reservoir and confining beds, or damage to well facilities. As
with flow data, injection pressure should be continuously recorded.
Pressure fall-off data collected after any extended period of continuous
operation can be used to check the performance of the reservoir as com-
pared with is original condition. However, it should be noted that the
72
-------
INJECTION WELL MONITORING
G
PRESSURE GAGE
WELLHEAD PRESSURE
r
FRESH-WATER-BEARING - —*••"-" — ™ —
SURFACE SANDS AND o . . ' o '.•
GRAVELS • « '. ' • o
— *" ..'•'.' o.
o • ° . •.«•<>
^"v_ - •-.-
IMPERMEABLE SHALE ' — -• _
• ' • * •
CONFINED FRESH-WATER-, .
BEARING SANDSTONE ... ' •
"' . .
IMPERMEABLE ~"JU — -~
SHALb V "' "" * —- - - ^^T"
\ — — —
s
s
V
\,
\
s
s
^
\
V
V
s,
s
S
s
S
S
s
\l
—
\
\
\ — —
\ ~ "~
\ ""~ "
_:' — ~~ —
— ™^" — ~~—
'•"~" — *~*^ — "
- "
PERMEABLE SALT-WATER- .''-.••'..
BEARING SANDSTONE •.•'/.-. ,
INJECTION HORIZON ',.,.•,, . ' .
l^s
^
Jv
^
^
^
V
y
" *"..'•• ';"-' : ;.'• "•'•'• ' •
•.'.'"•••".''.'.••'.•
&
/
^
-J
={l} PRESSURE GAGE O psi
^
^
s
\
N
S
s
^
s
s,
s
V
s
v
s
s
s
s
s
s
s
fj
/
f
S
f
/
f
t
/
/
/
/
f
/
f
f
» " • ' • o •
0* • . * ' °
I '*>'"•
0 ° ' » u
r -i — - — —
• • • • : . • • , . . '
* ' ,
'•
-=~ SURFACE CASING SEATED
~S BELOW FRESH WATER AND
/~ CEMENTED TO SURFACE
' n - — •
INNER CASING SEATED IN OR
r
«
d
^^
^
^
i
•*
M
s
s
s
V
>1
\,
>
s
s
V
>
s
^•1
..ABOVE INJECTION HORIZON
^ AND CEMENTED TO SURFACE
-—-
_ , - — . — —
,r^ INJECTION TUBING
— ANNULUS FILLED WITH
--*" NONCORROSIVE FLUID
"=- PACKERS TO PREVENT FLUID
^CIRCULATION IN ANNULUS
OPEN-HOLE COMPLETION IN
' COMPETENT STRATA
' \; ' ' •''. .'. ' ', '• .'
IMPERMEABLE SHALE
Figure 37. Schematic diagram of an industrial waste injection well completed
in competent sandstone (modified after Warner, 1965).
-------
SURVEILLANCE OF OPERATING WELLS
time scale of continuous recorders is not generally adequate for providing
data during the early period of a pressure fall-off test, so the continuously
recorded data will probably need to be supplemented with additional ob-
servations in order to have a complete record of the test.
Figure 28 (page 50) is an example of the pressure response that would
ideally be expected during a period of continuous injection. Pressure in-
crease through time should be linear on a semilogarithmic scale, after
an early period of adjustment.
In contrast with this ideal behavior, Figure 38 shows the injection
pressure history of a wastewater injection well completed in a carbonate
reservoir. Two marked periods of pressure decline are shown, one in
1967-1968 and one in 1970. The explanation for this is believed to be that
the wastewater being injected, initially an acid solution, reacted with the
carbonate reservoir to increase the permeability and thus decrease the
injection pressure. The period of gradual pressure increase during 1969-
1970 is probably the normal buildup following this initial period of perme-
ability increase. In 1970, the wastewater composition was changed to in-
clude a second acid stream. This new stream apparently caused additional
permeability increase and a temporary reduction in injection pressure,
after which the expected pressure buildup resumed.
Figure 39 shows the plots of two pressure fall-off tests performed in
an injection well of the Monsanto Company, Pensacola, Florida. This
well is also constructed in a carbonate aquifer. One test was made in
800
600
400
200-
IM7 (966 1969 1970 1971
YEAR
Figure 38. Pressure history of a well injecting into a carbonate aquifer.
74
-------
INJECTION WELL MONITORING
UJ
Ul
u.
60
100
120
140
160
ac
ui
180
200
JAN. 1969
/O a 975 gpm
o
NOV I967/
0 * 950 gpm
to
100
TIME, MINUTES
1000
10,000
Figure 39. Semi logarithmic plot of rwo pressure fall-off tests measured
in an injection well of the Monsanto Compart/, Pensacola,
Florida (Goolsby, 1971).
November 1967, before injection of an acidic wastewater stream began.
The other test was performed in January 1969, after the acidic wastewater
had been injected for nine months. The second test shows a much slower
rate of fall-off, indicating an increased permeability in the vicinity of the
well bore caused by reaction of the acidic wastewater with the carbonate
aquifer. This conclusion is substantiated by an increase in the injection
index for this and another well during the same time period, as shown in
Figure 40.
Some other possible causes of deviation from the ideal response are
the presence of hydrologic barriers of conduits, leaky confining beds,
and permeability reduction from suspended solids, chemical reactions,
etc. The variety of factors that may influence well behavior indicates
the need for maintaining an accurate, detailed well history so that the
probable cause of any unusual performance can be deduced and the ap-
propriate action taken.
Pressure in the casing-tubing annulus is monitored to detect any changes
that might indicate leakage through the injection tubing or the tubing-casing
packer. When a packer is used, the casing-tubing annulus pressure should
be zero, except perhaps for some pressure resulting from expansion of
75
-------
SURVEILLANCE OF OPERATING WELLS
16
16
2 l4
12
10
8
INJECTION INDEX • "if* *"* """
I/2(AP A + AP "8")
AP » BOTTOM - HOLE PRESSURE INCREASE
1963
1964
1965
1966
1967
1968
1969
Figure 40. Monthly average injection index of two injection wells of the
Monsanto Company, Pensacola, Florida (Goolsby, 1971).
the injection tubing. In cases where a packer is not used, pressure will
be exerted directly on the fluid in the annulus, and indication of leakage
would be a significant change in the annulus pressure.
Other methods of monitoring of the injection well also deserve mention.
The corrosion rate of well tubing and casing may be monitored by use of
corrosion coupons inserted in the well. A conductivity probe may be
used to detect a change in the chemistry of the fluid in the casing-tubing
annulus. In wells with packers the conductivity probe can be used to de-
tect tubing leaks, and in wells without tubing to detect shifts in the inter-
face between the injected fluid and the casing-tubing fluid. Another tech-
nique that has been used to monitor the casing-tubing annulus is continuous
cycling of the annulus fluid and analysis of the return flow for evidence of
contamination by wastewater.
PERIODIC INSPECTION AND TESTING
Sufficient incidents have occurred in the past to emphasize the need
for periodically inspecting or testing the subsurface facilities of injection
wells, particularly when chemically reactive wastes are being injected.
One such incident was the rather spectacular failure of a wastewater in-
jection well at the Hammermill Paper Mill, Erie, Pennsylvania. In that
76
-------
PERIODIC INSPECTION AND TESTING
instance, the well casing parted as a result of corrosion and a portion of
it was reportedly lifted from the hole by fluid pressure. Substantial loss
of wastewater into Lake Erie and abandonment of the well resulted. Other
cases have been reported in which portions of tubing or casing have failed
by corrosion and caused temporary or permanent shutdown of the well.
There may also be reason to examine the well bore to check for the loca-
tion of zones of wastewater entrance, enlargement due to chemical reac-
tion, the location and orientation of induced fractures, buildup or precipi-
tates or filtered solids, etc. Examples are available of wells that have
been abandoned or modified because of borehole enlargement that led to
collapse of the borehole or damage to the casing or cement near the bot-
tom of the casing string.
Methods of inspection of casing, tubing, cement and the well bore are:
• Pulling of tubing and visual or instrumental inspection
• Inspection of casing or tubing in place, using magnetic logs
• Inspection of casing, tubing, or the well bore with caliper
or televiewer logs
• Pressure testing of casing
• Inspection of casing cement with cement bond logs
• Inspection of casing, cement, or the well bore with injec-
tivity or temperature profiles or other appropriate logs.
The process of pulling and inspecting tubing is self-explanatory. Me-
chanical methods are available, for example, for inspection of lined steel
tubing for flaws in the lining. Individual joints of tubing can be pressure
tested at the surface for leakage.
Magnetic down-hole casing or tubing inspection services are provided
by oil field service companies. These logs indicate, by virtue of the elec-
tromagnetic response of steel pipe, the relative pipe thickness. Thin
areas may indicate corrosion or other damage. If such a log is run early
in the life of the pipe, then logs run after the well has been in operation
are much more easily interpreted. Figure 41 shows the response of a
pipe inspection log and photographs of the casing that was pulled after
running the log. Figure 42 is a portion of a pipe inspection log from a
wastewater injection well which indicates possible corrosion in the inter-
val from 1480 to 1510 feet; regular deflections on the log represent casing
joints. Corrosion could either be on the inside or the outside of the casing.
Caliper logs provide a record of the inside diameter of pipe or bore-
hole walls and may show intervals of pipe corrosion, borehole enlarge-
ment, or borehole plugging at the formation face. Figure 43 shows
77
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SURVEILLANCE OF OPERATING WELLS
PHASE SHIFT PHASE SHIFT
0° 360° 0° 100
f M I I I I I I I
JOMt '19-fcltOT 3' MWffl*CmM
Mth siMral MUD hota.
tort '20-MtM tao ftwft rf tort
wtrtly coirodtd with wwil l(i|t
koto 1" to 2" « duMttr. (OHM 2'
hn MttMiw cvroiiOT «Hk i
I I I I t=4=i
IOMI'21 - SMMMy cvraM ww tap
tao ft** of**
i
Figure 41. Pipe Inspection Log and photographs of casing pulled after
log was run to verify the log (Schlumberger, 1970).
portions of a caliper log run before injection and after 5 years of injection
of an acidic wastewater into a limestone aquifer. The log indicates con-
siderable borehole enlargement as a result of dissolution of the limestone
by the injected acidic waste in the interval from 1500 to 1600 feet. It
would be reasonable to conclude that most of the wastewater entered that
interval.
Borehole televiewers provide an image of the pipe of borehole wall
as produced by the reflection of sound waves emitted from a sonde. The
combination sound source and receiver is highly directional and is ro-
tated rapidly as the tool is moved up the hole. Thus, the hole is contin-
uously scanned. The resulting information is displayed on an oscilloscope
and a film made of the scope display. The picture obtained depicts the
well bore as though it were split open and laid out for inspection. Figure
44 illustrates the detail with which the borehole televiewer can indicate
casing damage. In Figure 45 vertical fractures in the borehole wall of
a well in Oklahoma are shown.
Pressure testing can be used to detect casing leaks and it is required
by law in many oil-producing States as a method of testing the integrity
of casing in new wells at the time that the casing is cemented into the
borehole. In such tests, a cement plug is left at the bottom of the cas-
ing during cementing and allowed to harden. The interior of the casing
78
-------
PERIODIC INSPECTION AND TESTING
Bl
1400'
-I ' -\ DECREASING CASING
THICKNESS
=*•
~^L (1 division - 0.0084 in.) 1
1500'
POSSIBLE
CORRODED i
ifciTr?r»w A i T
Figure 42. Portion of a casing inspection log run in a wastewater injection
well showing possible corrosion in the interval from 1480 to
1510 feet.
79
-------
SURVEILLANCE OF OPERATING WELLS
July 1966
September 1971
1400
1500
1600
UJ
UJ
UJ
«r
en
o
| 1700
UJ
m
0.
UJ
O
1800
1900 L
1400
1500
1600
1700
1800
UJ
UJ
UJ
or
en
o
1
UJ
OD
o.
UJ
JI900
t
16
0 8 12 16 20 24 28
36
DIAMETER, IN INCHES
DIAMETER, IN INCHES
Figure 43. Preinjectlon and postlnjection caliper logs from a wastewater
injection well at Belle Glade, Florida, showing solution of
the limestone aquifer in the 1500- to 1600-ft interval by
acidic wastewater (Black, Crow, and Eidsness, 1972).
80
-------
PERIODIC INSPECTION AND TESTING
BOREHOLE TELEVIEWER
-:-.-:!•.•.::;:• .;••/:•:
l^f:l|[l';G;£:Sl|r:;s'!:;|l:
-- ."-jjijy1-;, :•.•.::-." •••":••.'::':''• :.•;'•";--.•;-.•:;•,
.. - &".:.•: . .:•' '.' V.-;y>.-:;•'.> >:"
ilf^iil
•«;; :.*:
4465-
PERFORATIONS
4 SHOTS/FT.
PHASED 120°
OLD PACKER SEAT
(DRILLED OUT)
CASING COLLAR
CASING INSPECTION
Figure 44. Borehole televiewer log of a section of casing showing
casing perforations, packer seat, and casing collar
(Schlumberger, 1970).
is then subjected to a specified amount of fluid pressure (0. 2 psi per foot
of casing in Texas). * Rapid decline in pressure indicates leakage from
the casing. Such a test could also be performed periodically in operating
wells by setting temporary plugs or using packers.
The cement-bond log is used to determine the quality of the casing -
cement bonding and to detect channels in the cement behind the casing,
or to detect damage to cement from high-pressure injection of chemical
reaction. The cement-bond log is a continuous measurement of the am-
plitude of elastic waves after they have traveled through a short length
of pipe, cement, and perhaps formation (Figure 46). The amplitude of
the elastic wave is maximum in uncemented casing and will generally be
lower as the degree of bonding and integrity of the cement improves.
*Texas Railroad Commission rules.
81
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SURVEILLANCE OF OPERATING WELLS
3540
5550
SMO
Figure 45. Borehole televiewer log showing
vertical fractures in the borehole
wall of a well in Oklahoma
(Zemaneketal., 1970).
82
-------
PERIODIC INSPECTION AND TESTING
TRANS
REC.
CASING
ONDED CEMENT
/SHEATH/
SONIC PULSE
WAVE FRONT
'::"••;! ^"FORMATION"
* • * * • / _— ^_/"""—""
BORE
HOLE
LIQUID
Figure 46. Schematic diagram of a cement bond logging tool
in a borehole (Grosmangin et al., 1960).
Thus, the relative amplitudes of the waves in different portions of a well
can be interpreted to indicate the condition of the cement and degree of
bonding. Complications that occur in the interpretation of cement-bond
logs are discussed be Fertl et al. (1974). Figure 47 shows portions of a
cement-bond log from an acid wastewater injection well. It appears that
the casing in the vicinity of 1900 to 2000 feet is not bonded. The interval
from 2700 to 2800 feet, near the base of the casing, shows progressively
better bonding between the casing and cement.
Some other possible inspection methods are radioactive tracer injec-
tivity profiles, flow-meter injectivity profiles, and temperature profiles.
The objective of these methods is to determine where injected fluid is
going. Radioactive tracer injectivity profiles accomplish this through
injection of a radioactive tracer and logging of the borehole with a gamma
ray detector. The detector measures concentrations of tracer, which in-
dicate paths of tracer flow. Flow-meter injectivity profiles are similar,
except that flow paths of injected fluid are indicated by a flow meter rather
than by an injected tracer. Temperature profiles may indicate anomalies
at points where injected fluids enter the receiving formation or where they
escape through casing or tubing leaks. Such anomalies would obviously
be most likely to be detectable in wells where significant temperature con-
trasts exist between injected fluids and the aquifers.
83
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SURVEILLANCE OF OPERATING WELLS
1900
2000
=====3==5£3=:5335555=
0-10 — 20— 50MOO
2700
2800
PERCENT UNBONDED
PIPE SIGNAL
Figure 47. Portions of a cement-bond
log from an acid wastewater
Injection well.
84
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MONITORING WELLS
Repetitive running of resistivity or radioactive logs may also be used
to locate the zones that are accepting injected wastewater. Resistivity
logs are limited to the uncased portion of a well, but radioactive logs
have been used to locate a freshwater-saline water interface behind casing
(Keys and MacCary, 1973).
MONITORING WELLS
The subject of monitoring wells has been a controversial one in regula-
tion of wastewater injection. Such wells are routinely used in shallow
groundwater studies but are less frequently used in conjunction with waste-
water injection, for reason's that will be examined.
At least three hydrogeologically different types of monitor wells can
be and have been constructed, each with different objectives as shown
below:
Well Type
1. Constructed in receiving
aquifer — nondischarging
2. Constructed in or just
above confining unit
—nondischarging
3, Constructed in a fresh-
water aquifer above
receiving aquifer
Objective
A. Obtain geologic data
B. Monitor pressure in
receiving aquifer
C. Determine rate and
direction of wastewater
movement
D. Detect geochemical
changes in injected
wastewater
E. Detect shifts in
f r e s hwate r - s aline
water interfaces
A. Obtain geologic data
B. Detect leakage through
confining unit
A. Obtain geologic data
B. Detect evidence of fresh-
water contamination
Monitor wells constructed in the receiving aquifer are normally non-
discharging because a discharging well would defeat moat of the purposes
of this type of monitor well. Also, the produced brines would have to be
disposed of. Although it is not normally necessary to monitor pressure
in the receiving aquifer except at the injection well, special monitor wells
may be desired where pressure at a distance from the injection well is of
concern because of the presence of known or suspected faults or aban-
doned wells that may be inadequately plugged. The pressure response in
85
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SURVEILLANCE OF OPERATING WELLS
a monitor well at such locations would indicate the extent of danger of
flow through such breaches in the confining beds and possibly also indi-
cate whether leakage was occurring.
Constructing a monitor well or wells in the receiving aquifer is the
only direct means of verifying the rate and direction of wastewater move-
ment. More than one well will frequently be necessary to meet this ob-
jective, because monitor wells of this type only sample wastewater plumes
that pass directly through the well bore; and nonuniformity in aquifer por-
osity and permeability can cause the wastewater to arrive very rapidly
or perhaps not at all at a particular well. A single well might be satis-
factory where aquifer and fluid properties are such that it is judged most
likely that wastewater movement will be radial and reasonably uniform
ox where the objective is to detect wastewater arrival at a particular
point of interest. These same comments apply to wells intended to de-
tect geochemical changes in injected wastewater. A difference is that a
well for monitoring geo chemical changes would be placed near enough to
the injection well so that the wastewater front will arrive within a rela-
tively short time, whereas, a well for detecting wastewater arrival at a
point of concern might be beyond the expected ultimate travel distance of
the wastewater.
A well intended to detect a shift in a freshwater-saline water interface
should be located either within that interface or in the freshwater portion
of the aquifer just beyond the interface. Because movement of this inter-
face will be in response to increased aquifer fluid pressure, rather than
to actual displacement by the wastewater front, detection of its movement
should be possible with a small number of observation wells, perhaps
even a single properly located one. It is possible to estimate rates of
movement for a particular case and to determine if a monitor well is
likely to be able to detect such a shift. Monitoring would be for confirm-
ation of the calculations and to allow for revisions in regulation if unex-
pected results occur.
Negative factors should be considered in any case where deep monitor
wells are contemplated: monitor wells in the receiving aquifer may be
of limited usefulness, and they provide an additional means by which in-
jected wastewater could escape from the receiving aquifer. In a number
of cases, multiple injection wells have been constructed at a site, one or
more of which may be standby injection wells. Standby wells can be used
for monitoring of aquifer pressure, and for sampling of aquifer water.
However, if they have been operated or even extensively tested, their use
for monitoring may be impaired.
Some examples of the use of observation wells in the receiving aquifer
are given by Goolsby (1971 and 1972), Kaufman et al. (1973), Leenheer and
Malcom (1973), Peek and Heath (1973), and Hanby and Kidd (1973).
86
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MONITORING WELLS
For detection of leakage, the principal of using nondischarging monitor
wells completed in the confining beds or in a confined aquifer immediately
above the confining beds has been widely discussed but has been little used.
This type of well has the potential for acting as a very sensitive indicator
of leakage by allowing measurement of small changes in pressure (or water
level) that accompany leakage. A well of this type is best suited for use
where the confining unit is relatively thin and well defined and where the
engineering properties of the two aquifers are within a range such that
pressure response in the monitored aquifer will be rapid if leakage occurs.
Use of the concepts outlined by Witherspoon and Neuman (1972) will allow
evaluation of the possibilities of success of this monitoring method in a
specific situation. In many actual cases, confining beds are several hun-
dred to several thousand feet thick and do not contain aquifers suitable for
such monitoring. In other cases, the physical circumstances are amenable
to such monitoring but several thousands of feet of interbedded aquitards
and saline water aquifers are present; in these cases, slow vertical leak-
age across the aquitard immediately over the injection interval is not sig-
nificant because it can be predicted that there will be no measurable influ-
ence at the stratigraphic level where freshwater or other resources occur.
Two good examples of the usefulness of monitoring an aquifer immedi-
ately above the confining beds are provided by Kaufman et al. (1973) and
Leenheer and Malcolm (1973). In the case described by Kaufman et al.,
wastewater leakage from the lower Floridan aquifer through 150 feet of
confining beds into the upper Floridan aquifer was detected by geochemi-
cal analysis of water from a monitor well constructed in the upper Flori-
dan aquifer. No pressure effects were noticed in this instance. Leenheer
and Malcolm summarized a case history in which leakage through the con-
fining beds was detected first by pressure increase in an overlying aquifer,
and later confirmed by chemical analysis which showed wastewater con-
tamination of water in the aquifer.
The type of monitor well most commonly in use is that which is com-
pleted in a freshwater aquifer above the injection horizon for detecting
freshwater contamination. In a number of locations, this type of monitor-
ing is provided by wells that are a part of the plant's water supply system.
In other cases, the wells have been constructed particularly for monitor-
ing and are not used for water supply. Wells for detection of freshwater
contamination should be discharging wells because they then sample an
area of aquifer within their cone of depression. As previously mentioned,
nondis charging wells are of limited value for detection of contamination
because they sample only that water that passes through the well bore.
Wells for monitoring freshwater contamination should be located close to
the anticipated sources of contamination, which are:
87
-------
SURVEILLANCE OF OPERATING WELLS
• The injection well itself
• Other nearby deep wells, active or abandoned
* Nearby faults or fracture zones.
No example is known to the writer where monitor wells of this type
have detected wastewater contamination of a water supply aquifer.
In the preceding discussion, it has been implied that separate wells
would need to be constructed for surveillance of aquifers and aquicludes
at different depths. This is not necessarily the case. Talbot (1972)
shows how the injection well itself can be adapted for monitoring of over-
lying aquifers, and also how monitor wells may be constructed for sur-
veillance of more than one aquifer. Wilson et al. (1973) describe a case
where the injection well was modified as shown in Figure 48 for monitor-
ing of two aquifers overlying the injection zone.
Since the objectives for each of the types of monitoring wells discussed
are worthwhile ones, why are monitor wells not more widely used? The
answer to this question is that the potential benefits are often judged to be
small in comparison with the costs and negative aspects. Therefore, such
wells may not be voluntarily constructed by the operating companies nor
required by the regulatory agencies. In particular, monitor wells con-
structed in the receiving aquifer are often difficult to justify because
such wells are the most expensive form of surveillance and may yield
very little information that is important for regulation. It can reasonably
be concluded that monitor wells should not be arbitrarily required, but
should be used where the local circumstances justify them.
OTHER MONITORING METHODS
A method of monitoring not so far mentioned is the sampling of springs,
streams, or lakes that could be affectedly injection. There are few in-
stances where such monitoring would be applicable; but, for example
where springs originate along a fault within the area of pressure influence
of the injection well an increase in discharge rate or change in water qual-
ity could be an indication of leakage of formation water along the fault in
response to the increased pressure from injection. Also, springs and
gaining streams act similarly to discharging wells in that they provide a
composite sample of groundwater over their area of influence; thus, they
might reveal leakage from unknown fracture zones or abandoned wells
that connect a shallow groundwater aquifer with the injection interval. In
a similar way, lakes may be collecting points for groundwater seepage or
streams and may reflect quality changes in shallow groundwater aquifers.
-------
u
UJ
CO
1000
< 2000
I
UJ
3000
Ul
UJ
u.
a.
ui
o
4000
5000
"W».PM
. Oiigocene
—
Eocene
-
Poleoceno
Lot*
Cretaceous
Y/S<
U
"C 3
O V
C»
H
0
(A
< Anhydrite- >
* dolomite y
^ confining beds*
•- 8
'o C
• 8
'iT
Tempo -Hawthorn- surf iciol
Suwonnee Limestone .
Ocolo
Avon
Loke
Group
Pork Limtston*
City Limtstont
Oldsmor LiiMtton* •
•
o
w
'jk
»
2
e
U
Upoor
Middle
Lower
Lowton Lim»ston«
ond b«d» of
Toylor og* (?)
30" Cosing
24" Casing
Cement grout
Shollow monitor
well
Cosing
Detp monitor
well
iff Cosing
o
Packer
Fiberglass
injection
tubing
6^- Open hole
Figure 48. Geologic column and construction of a wastewater injection well at Mulberry, Florida, where two
aquifers above the injection zone are monitored through the injection well (Wilson et a I., 1973).
m
70
O
z
z
o
o
o
CO
-------
SURVEILLANCE OF OPERATING WELLS
Surface geophysical methods offer some limited possibilities for
monitoring of wastewater injection. Barr (1973) discussed the feasibility
of monitoring the distribution of injected wastewater with seismic reflec-
tion. Monitoring by seismic reflection depends on the existence of a suf-
ficient density contrast between injected and interstitial water, and no
field trials of monitoring by seismic reflection have been reported. Elec-
trical resistivity surveying could be useful for monitoring the movement
of freshwater-saline water interfaces or for detecting saline water pollu-
tion of freshwater aquifers (Swartz, 1937; Warner, 1969).
Monitoring for earthquake occurrence is accomplished by use of a net-
work of seismometers placed in the vicinity of the injection well and in
the vicinity of nearby faults along which seismic events might be triggered.
Examples of this form of monitoring are described by Raleigh (1972) and
by Hanby and Kidd (1973). In a case where earthquake stimulation is con-
sidered a possibility, seismic monitoring should begin before the well is
operated to obtain background data.
90
-------
SECTION V11I
REFERENCES
Barr, F. J., Jr., "Feasibility Study of a Seismic Reflection Monitoring
System for Underground Waste-Material Injection Sites, " in
Underground Waste Management and Artificial Recharge,
Jules Braunstein, ed, p 207-218, 1973.
Bear, Jacob, Dynamics of Fluids in Porous Media, Elsevier Publishing
Co., New York, 764 pages, 1972.
Bear, J., and M. Jacobs, Th.e Movement of Injected Water Bodies in
Confined Aquifers, Underground Water Storage Study Report
No. 13, Technion, Haifa, Israel, 1964.
Berry, F.A.F., "High Fluid Potentials in California Coast Ranges and
their Tectonic Significance, " Bull. Am. Assoc. Petroleum
Geologists, Vol.57, No. 7, p 1219-1249, 1973.
Black, Crow, and Eidsness, Inc., Engineering Report on Modification to
Deep-Well Disposal System; Effect of Monitoring Wells and Future
Monitoring Requirements for Sugar Cane Growers Cooperative of
Florida, Belle Glade, Palm Beach County. Florida, Engr. Rept.
Proj. No. 387-71-01, 40 pages, 1972.
Bond, D. C., Hydrodynamics in Deep Aquifers of the Illinois Basin, Illinois
State Geological Survey Circular 470, 72 pages, 1972.
Bond, D. C., "Deduction of Flow Patterns in Variable-Density Aquifers
from Pressure and Water-Level Observations, " in Underground
Waste Management and Artificial Recharge, Jules Braunstein,
ed, Am. Assoc. Petroleum Geologists, Tulsa, Oklahoma,
p 357-378, 1973.
Bredehoeft, J. D., and G. F. Pinder, "Application of Transport Equations
to Groundwater Systems," in Underground Waste Management and
Environmental Implications, T.D. Cook, ed, Am. Assoc. Petro-
leum Geologists Memoir 18, p 191-199, 1972.
Brown, D. L., andW.D. Silvey, "Underground Storage and Retrieval
of Fresh Water from a Brackish-Water Aquifer, " in Underground
Waste Management and Artificial Recharge, Jules Braunstein,
ed, Am. ASSOC. of Petroleum Geologists, Tulsa, Oklahoma,
p 379-419, 1973.
91
-------
REFERENCES
Buschbach, T.C., Cambrian and Ordovician Strata of Northeastern
Illinois, Illinois Geol. Survey Report of Investigations 218,
90 pages, 1964.
Clifford, M. J., "Hydrodynamics of the Mount Simon Sandstone, Ohio
and Adjoining Areas," in Underground Waste Management and
Artificial Recharge, Jules Braunstein, ed, Am. Assoc. of
Petroleum Geologists, Tulsa, Oklahoma, p 349-356, 1973.
Cook, T. D., ed, Underground Waste Management and Environmental
Implications. Am. Assoc. of Petroleum Geologists Memoir 18,
412 pages, 1972.
Davis, S.H., and R. J.M. De Weist, Hydrogeology. Wiley and Sons, Inc.,
New York, New York, 463 pages, 1966.
Dickinson, George, "Geological Aspects of Abnormal Reservoir Pres-
sures in the Gulf Coast Louisiana," Am. Assoc. Petroleum
Geologists Bull.. Vol. 37, No. 2, p 410-432, 1953.
Eisenberg, D., and W. Kauzmann, The Structure and Properties of
Water. Oxford University Press, New York, New York, 296
pages, 1969.
Ferris, J. G., et al., Theory of Aquifer Tests. U.S. Geological Survey
Water Supply Paper 1536-E, 174 pages, 1962.
Fertl, W.H., et al., "A Look at Cement Bond Logs, " Jour, of Petro-
leum Technology, Vol 26, p 607-617, June 1974.
Gatlin, Carl, Petroleum Engineering Drilling and Well Completions.
Prentice-Hall, Inc., Englewood Cliffs, N. J., I960.
Gelhar, L. W., and others, Density Induced Mixing in Confined Aquifers.
U.S. Environmental Protection Agency Water Pollution Control
Research Series Publication 16060 ELJ 03/72, 1972.
Goolsby, D. A., "Hydrogeo chemical Effects of Injecting Wastes into a
Limestone Aquifer near Pensacola, Florida, " Ground Water
Vol 9, No. 1, p 13-19, 1971. ;—! '
Goolsby, D. A., "Geochemical Effects and Movement of Injected Indus-
trial Waste in a Limestone Aquifer, " in Underground Waste
Management and Environmental Implications. Am. Assoc. of
Petroleum Geologists Memoir 18, Tulsa, Oklahoma, p 355-367,
1 7/2.
Gould, H.R., History of the AAPG Geothermal Survey of North America,
unpublished paper presented at the 1974 Am. Assoc. of Petroleum
Geologists Annual Meeting, San Antonio, Texas, 1974.
92
-------
REFERENCES
Grosmangin, M., et al., "A Sonic Method for Analyzing the Quality of
Cementation of Borehole Casings, " Jour, of Petroleum Tech-
nology, p 165-171, February 1961.
Hall, C.W., and R.K. Ballentine, "U.S. Environmental Protection Agency
Policy on Subsurface Emplacement of Fluids by Well Injection, "
in Underground Waste Management and Artificial Recharge, Jules
Braunstein, ed, Am. Assoc. of Petroleum Geologists, Tulsa,
Oklahoma, p 783-793, 1973.
Hanby, K. P. , and R.E. Kidd, "Subsurface Disposal of Liquid Industrial
Wastes in Alabama—A Current Status Report, " in Underground
Waste Management and Artificial Recharge, Jules Braunstein,
ed, Am. Assoc. Petroleum Geologists, Tulsa, Oklahoma,
p 72-90, 1973.
Hanshaw, B.B., "Natural Membrane Phenomena and Subsurface Waste
Emplacement," in Underground Waste Management and Environ-
mental Implications, T. D., Cook, ed, Am. Assoc. of Petroleum
Geologists Memoir 18, Tulsa, Oklahoma, p 308-315, 1972.
Haun, J.D., and L. W. Le Roy, eds, Subsurface Geology in Petroleum
Exploration, Colorado School of Mines, Golden, Colorado, 1958.
Hubbert, M.K., and D.G. Willis, "Mechanics of Hydraulic Fracturing, "
in Underground Waste Management and Environmental Implica-
tions, T.D. Cook, ed, Am. Assoc. of Petroleum Geologists
Memoir 18, Tulsa, Oklahoma, 411 pages, 1972.
Illinois Water Survey, Feasibility Study of Desalting Brackish Water
from the Mt. Simon Aquifer in Northeastern Illinois, Urbana,
Illinois, 120 pages, 1973.
Jans sens, A., Stratigraphy of the Cambrian and Lower Ordovician Rocks
in Ohio, Ohio Division of Geological Survey Bulletin 64, 197 pages,
1973.
Jennings, H.Y., and A. Timur, "Significant Contributions in Formation
Evaluation and Well Testing, " Jour. Petroleum Technology,
Vol 25, p 1432-1446, December 1973.
Katz, D. L., andD.L. Coats, Underground Storage of Fluids, Ulrich's
Books, Inc., Ann Arbor, Michigan, 575 pages, 1968,
Kaufman, et al. , "Injection of Acidic Industrial Waste in a Saline Car-
bonate Aquifer," in Underground Waste Management and Arti-
ficial Recharge, Jules Braunstein, ed, Am. Assoc. Petroleum
Geologists, Tulsa, Oklahoma, p 526-551, 1973.
Kehle, R. O., "The Determination of Tectonic Stresses through Analysis
of Hydraulic Well Fracturing," Jour. Geophys. Research, Vol. 69
No. 2, p 259-273, 1964.
93
-------
REFERENCES
Keys, W.S. , and R.F. Brown, "Role of Borehole Geophysics in Under-
ground Waste Storage and Artificial Recharge, " in U nderground__
Waste Management and Artificial Recharge, Jules Braunstein,
ed, Am. Assoc. of Petroleum Geologists, Tulsa, Oklahoma,
p 147-191, 1973.
Keys, W.S., andL.M. MacCary, Location and Characteristics of the
Interface between Brine and Fresh Water from Geophysical
Logs of Boreholes in the Upper Brasos River Basin, Texas,
U.S. Geological Survey Prof. Paper 809-B, 23 pages, 1973.
Kirkpatrick, C. V., "Formation Testing, " The Petroleum Engineer,
p B-139, 1954.
Kruseman, G. P., and N. A. DeRidder, Analysis and Evaluation of Pump-
ing Test Data, International Institute for Land Reclamation and
Improvement, Bulletin 11, Wageningen, The Netherlands, 200
pages, 1970.
Leenheer, J. A., and R. L. Malcolm, "Case History of Subsurface Waste
Injection of an Industrial Organic Waste," in Underground Waste
Management and Artificial Recharge, Jules Braunstein, ed, Am.
Assoc. Petroleum Geologists, Tulsa, Oklahoma, p 565-584, 1973.
Lohman, S.H., Ground-Water Hydraulics, U.S. Geol. Survey Prof.
Paper 708, 70 pages, 1972.
Lynch, E. J., Formation Evaluation, Harper and Row, New York, New
York, 422 pages, 1962.
Matthews, C.S., and D. G. Russell, Pressure Buildup and Flow Tests in
Wells, Am. Inst. of Mining, Met., and Petr. Engrs., Soc. of
Petroleum Engrs., Monograph Vol 1, 1967.
Moore, C.A., ed, Second Symposium on Subsurface Geological Techniques,
University of Oklahoma Extension Division, Norman, Oklahoma,
1951.
Murphy, W. C., The Interpretation and Calculation of Formation Charac-
teristics from Formation Test Data, Halliburton Services, Duncan,
Oklahoma, undated.
Ohio River Valley Water Sanitation Commission, Underground Injection of
Wastewater in the Ohio Valley Region, Cincinnati, Ohio, 63 pages,
1973.
Pe^k, H.M. , and R. C. Heath, "Feasibility Study of Liquid-Waste Injection
into Aquifers Containing Salt Water, Wilmington, North Carolina,"
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homa, p 851-878, 1973.
94
-------
REFERENCES
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Englewood Cliffs, New Jersey, 326 pages, 1963.
Raleigh, C. B. , "Earthquakes and Fluid Injection, " in Underground Waste
Management and Environmental Implications, T.D. Cook, ed,
Am. Assoc. of Petroleum Geologists Memoir 18, p 273-279,
1972.
Robertson, J.B., and J. T Barraclough, "Radioactive- and Chemical-
Waste Transport in Groundwater at National Reactor Testing
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Underground Waste Management and Artificial Recharge, Jules
Braunstein, ed, Am. Assoc. Petroleum Geologists, Tulsa,
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Sbar, M.L., and M.L. Sykes, "Contemporary Compressive Stress and
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96
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APPENDIX
EPA POSITION ON SUBSURFACE EMPLACEMENT OF FLUIDS
The material in this appendix is reproduced from the Federal Register
of April 9, 1972, pp 12922-12933. (See also Hall and Ballentine, 1973)
INTRODUCTORY COMMENTS
The Environmental Protection Agency.
in concert with the objectives of the Fed*
eral Water Pollution Control Act, as
amended (33 U.S.C. 1251 et aeq.; 86 Stat.
816 et seq.; Pub. L. 92-500) "... to
restore and maintain the chemical, phy-
sical, and biological integrity of the Na-
tion's water" has established an EPA
policy on Subsurface Emplacement of
Fluids by Well Injection" which was is-
sued internally as Administrator's Deci-
sion Statement No. 5. The purpose of the
policy is to establish the Agency's con-
cern with this technique for use In fluid
storage and disposal and its position of
considering such fluid emplacement only
where it is demonstrated to be the most
environmentally acceptable available
method of handling fluid storage or dis-
posal. Publication of the Policy as In-
formation establishes the Agency's posi-
tion and provides guidance to other Fed-
eral Agencies, the States, and other In-
terested parties.
Accompanying the policy statement
are "Recommended Data Requirements
for Environmental Evaluation of Sub-
surface Emplacement of Fluids by Well
injection wen system: and to insure
ments is to provide guidance for potential
injectors and regulatory agencies con-
cerning the kinds of information re-
quired to evaluate the prospective
injections well system; and to insure
protection of the environment. The
Recommended Data Requirements re-
quire sufficient Information to evaluate
complex Injection operations for haz-
ardous materials, but may be modified
In scope by a regulatory agency for
other types of Injection operations.
The EPA recognizes that for certain
industries and in certain locations the
disposal of wastes and the storage of
fluids hi the subsurface by use of well
injection may be the most environmen-
tally acceptable practice available. How-
ever, adherence to the policy requires
the potential injector to clearly demon-
strate acceptability by the provision of
technical analyses and data justifying
the proposal. Such demonstration re-
quires conventional engineering and
other analyses which indicate beyond
a reasonable doubt the efficacy of the
proposed injection well operation.
Several issues within the policy should
be highlighted and explained to avoid
confusion. One of the goals of the pol-
icy is to protect the Integrity of the
subsurface environment. In the context
of the policy statement, integrity means
the prevention of unplanned fracturing
or other physical impairment of the geo-
logic formations and-the avoidance of
undesirable changes in aquifers, mineral
deposits or other resources. It is recog-
nized that fluid emplacement by well
injection may cause some change in
the environment and, to some extent,
may preempt other uses.
Emplacement is intended to include
both disposal and storage. The differ-
ence between the two terms is that stor-
age implies the existence of a plan for
recovery of the material within a rea-
sonable time whereas disposal implies
that no recovery of the material is
planned at a given site. Either opera-
tion would require essentially the same
type of information prior to injection.
However, the attitude of the appropriate
regulatory agency toward evaluation of
the proposals would be different for each
type operation. The EPA policy recog-
nizes the need for injection wells in cer-
tain oil and mineral extraction and fluid
storage operations but requires sufficient
environmental safeguards to protect
other uses of the subsurface, both dur-
ing the actual Injection operation and
after the Injection has ceased.
The policy considers waste disposal by
well injection to be a temporary means of
disposal hi the sense that it is approved
only for the life of an issued, permit.'
Should more environmentally acceptable
disposal technology become available, a
change to such technology would be re-
quired. The term "temporary" is not in-
tended to Imply subsequent recovery of
97
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APPENDIX
injected waste for processing by another
technology.
Paragraph 5 of the policy and program
guidance provides that EPA will apply the
policy to the extent of its authorities in
conducting all EPA program activities.
The applicability of the policy to partici-
pation by the several States In the
NPDES permit program under section
402 of the Federal Water Pollution Con-
trol Act as amended has been established
previously by { 124.80(d) of Part 124 en-
titled "State Program Elements Neces-
sary for Participation In the National
Pollutant Discharge Elimination Sys-
tem." 37 PR 28390 (December 22, 1972).
These guidelines provide that each EPA
Regional Administrator must distribute
the policy to the Director of a State water
discharge permit Issuing agency, and
must utilize the policy In his own review
of any permits for disposal of pollutants
Into wells that are proposed to be issued
by States participating in the NPDES.
Dated: April 2,1974.
JOHN OVARIES,
Acting Administrator.
ADMINISTRATOR'S DECISION STATEMENT
NO. 5 EPA POLICY ON SUBSURFACE
EMPLACEMENT OP FLUIDS BY WELL
INJECTION
This ADS records the EPA'* position on in-
jection wells and subsurface emplacement of
fluids by well injection. Mid supersedes the
Federal Water Quality Administration's order
COM 6040.10 of October 15. 1970.
Goals. The EPA Policy on Subsurface Em-
placement of Fluids by Well Injection Is
designed to:
(1) Protect the subsurface from pollu-
tion or other environmental hazards attrib-
utable to Improper Injection or Ill-sited In-
jection wells.
(2) Ensure that engineering and geological
safeguards adequate to protect the integrity
of the subsurface environment are adhered
to In the preliminary Investigation, design.
construction, operation, monitoring and
abandonment phase* of Injection well proj-
ects.
(3) Encourage development of alternative
means of disposal which afford greater en-
vironmental protection.
Principal finding* ant policy rationale.
The available evidence concerning Injection
wells and subsurface emplacement of fluids
Indicates that:
(1) The emplacement of fluids by subsur-
face Injection often Is considered by govern-
ment and private agencies as an attractive
mechanism for final disposal or storage owing
to: (a) the diminishing capabilities of sur-
face waters to receive effluents without vio-
lation of quality standards, and (b) the
apparent tower costs of this method of dis-
posal or storage over conventional and ad-
vanced waste management techniques.
Subsurface storage capacity is a natural re-
source of considerable value and like any
other natural resource its use must be con-
served for maximal benefits to all people.
(9) Improper Injection of municipal or
Industrial wastes or Injection of other fluids
for storage or disposal to the subsurface en-
vironment could result In serious pollution
of water supplies or other environmental
hazards.
(3) The effects of subsurface Injection and
the fate of Injected materials are uncertain
with today's knowledge and could result In
serious pollution or environmental damage
requiring complex and costly solutions on a
long-term basis.
Policy and program guidance. To ensure
accomplishment of the subsurface protection
goals established above It Is the policy of the
Environmental Protection Agency that:
(1) The EPA will oppose emplacement of
materials by subsurface injection without
strict controls and a clear demonstration
that such emplacement will not Interfere
with present or potential use of the subsur-
face) environment, contaminate ground water
resources or otherwise damage the environ-
ment.
(3) All proposals for subsurface Injection
should be critically evaluated to determine
that:
(a) All reasonable alternative measures
have been explored and found less satisfac-
tory In terms of environmental protection;
(b) Adequate prelnjectlon tests have been
made for predicting the fate of materials
Injected;
(c) There Is conclusive technical evidence
to demonstrate that such injection will not
Interfere with present or potential use of
water resources nor result In other environ-
mental hazards:
(d) The subsurface injection system has
been designed and constructed to provide
maximal environmental protection;
(e) Provisions have been made for moni-
toring both the injection operation and the
resulting effects on the environment; .
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APPENDIX
well injection has been prepared to establUb
the Agenty's position on the u*e of this dls-
poeal and storage technique. To aid In Im-
plementation of the policy • recommended
data base for environmental evaluation has
been developed.
The following parameters describe the In-
formation which should be provided by the
Injector and are designed to provide regula-
tory agencies sufficient Information to evalu-
ate the environmental acceptability of any
proposed well Injection. A potential Injector
should Initially contact the regulatory au-
thority to determine the preliminary Investi-
gative and data requirements for a particular
Injection well as these may vary for different
kinds of injection operations. The appropriate
regulatory authority will specify the exact
data requirements on a case by ease basis.
(a) An accurate plat showing location and
surface elevation of proposed Injection welt
site, surface features, property boundaries.
and surface and mineral ownership at an
approved scale.
(b) Maps indicating location of water wells
and all other wells, mines or artificial pene-
trations, Including but not limited to oil and
gas wells and exploratory or test wells, shov-
ing depths, elevations and the deepest forma-
tion penetrated within twice the calculated
zone of influence of the proposed project.
Plugging and abandonment records for all oil
and gas tests, and water wells should accom-
pany the map.
(c) Maps indicating vertlcaj and lateral
limits of potable water supplies which would
include both short- and long-term variations
In surface water supplies and subsurface
aquifers containing water with less than
10000 mg '1 total dissolved solids. Available
amounts and present and potential uses of
these waters, as well as projections of public
water supply requirements must be consid-
ered.
(d) Descriptions of mineral resources pres-
ent or believed to be present In area of
project and the effect of this project on
present or potential mineral resources to the
area*
(e) Maps and cross sections at approved
scales illustrating detailed geologic structure
and a stratigrapble section (Including for-
mations, llthology, and physical characteris-
tics) for the local area, and generalized maps
and cross sections Illustrating the regional
geologic setting of the project.
(f) Description of chemical, physical, and
biological properties and characteristics of
the fluids to be injected.
' (B) Potentiometrtc maps at approved
scales and isopleth Intervals of the pro-
Dosed Injection horiBon and of those aquifers
SSmeWtely above and «~ «J»jWf"«
borleon. with copies of^ all *aa**"*?
charts, extrapolations, and data used In com-
ll(hf M&t of the location and nature
of present or potentially useable minerals
from the cone of Influence.
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
REPORT NO.
EPA-680/4-75-008
2.
3. RECIPIENT'S ACCESS!
TITLE AND SUBTITLE
MONITORING DISPOSAL-WELL SYSTEMS
6. REPORT DATE
July 1975
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
Prof. Don L. Warner (Consultant)
8. PERFORMING ORGANIZATION REPORT
GE74TMP-45
PERFORMING ORGANIZATION NAME AND ADDRESS
TEMPO, General Electric Center for Advanced Studies^
Santa Barbara, California
10. PROGRAM ELEMENT NO.
1H1326
.CONTRACT/GRANT NO.
EPA 68-01-0759
12. SPONSORING AGENCY NAME AND ADDRESS
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
P.O. Box 15QZ7. Las Vgpa«. WV «Q1 14
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
NA
15. SUPPLEMENTARY NOTES
Environmental Protection Agency Report No. EPA-680/4-75-008
16. ABSTRACT
The Environmental Protection Agency is required, under P. L. 92-500,
The Federal Water Pollution Control Act Amendments of 1972, to esta-
blish a system for the surveillance of the quality of the nation's surface
and ground waters. Enactment of P. L. 93-523, the Safe Drinking Water
Act, further requires that State programs in order to be approved, shall
include monitoring programs to prevent underground injection which en-
dangers drinking water sources. This report provides information con-
cerning the data needed for monitoring the subsurface injection of waste-
water through cased disposal wells, and discusses the methods and tools
available for obtaining the data. The procedures for using the data for
predicting the response of the receiving aquifer to injection are then out-
lined. Surveillance of operating disposal wells is reviewed. Numerous
examples are given throughout the text.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. cos*Tl Field/Group
Monitoring, 'Underground Waste Disposal, '"Industrial Wastes
*Disposal Wells, "Injection Wells, Groundwater Quality,
Groundwater, *Wastewater, Aquifer Characteristics, Pollution
Control, Aquifers, Aquifer Management, Groundwater
Management, Groundwater Movement, Observation Wells,
Liquid Wastes, Malenclaves
02F, 02K, 05B,
05G, 08A, 08E
18, DISTRIBUTION STATEMENT
Available from NTIS
19. SECURITY CLASS (ThisReport)'
UNCLASSIFIED
21. NO. OF PAGES
109
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
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