United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-149 Sept. 1981
Project Summary
Potential Environmental
Problems of Enhanced Oil and
Gas Recovery Techniques
Ron Beck, Robert Shore, Terry Ann Scriven, and Melinda Lindquist
This study identifies and analyzes
the various types of environmental
degradation that may occur as a result
of enhanced oil and gas recovery (EOR
and EGR). Three areas are emphasized:
(1) identification and analysis of data
on EOR/EGR-related pollutants, (2)
assessment of environmental impacts
and identification of possible controls,
and (3) recommendations for future
research. The following nine processes
were studied: steam injection, in-situ
combustion, CO2 miscible flooding,
micellar/polymer flooding, alkaline
flooding, improved waterflooding,
advanced hydraulic fracturing, chemi-
cal explosive fracturing, and direc-
tional drilling.
A critical review was conducted of
published and unpublished informa-
tion on the environmental impacts of
EOR and EGR. The effects of these
processes on air quality, groundwater
quality, water quantity, noise levels.
and their secondary impacts are the
main areas of analysis. Each of the
nine technological processes is anal-
yzed to determine pollution problems
that may occur from its development.
A single methodology is used to
determine the environmental impact
and risks imposed by the nine
processes.
This impact methodology is applied
to currently available environmental
data collected during the study. A
general impact assessment is per-
formed, and the uncertainties that
remain about potential environmental
effects are enumerated. The report
also includes an investigation of
control strategies, proposed data
collection and monitoring activities,
and recommendations for further
research on EOR/EGR environmental
concerns.
This Project Summary was devel-
oped by EPA's Municipal Environmen-
tal Research Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This study identifies the areas of
environmental concern surrounding the
development of enhanced oil and gas
recovery {EOR and EGR) and assesses
the potential environmental hazards
posed by these operations as they
existed in early 1979. EOR in this report
refers to the tertiary stage of oil recovery
applied to oil fields where the reservoir
can no longer be economically produced
using natural reservoir pressure (pri-
mary recovery) or by water flooding to
push the oil to the surface (secondary
recovery). Processes that make use of
additional forms of energy, such as
chemical or thermal, are used to
achieve further oil production. EGR
similarly applies to gas-bearing sands.
Nine enhanced recovery technologies
and discussed along with the various
categories of pollutants associated with
them (Figure 1 and Table 1).
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Micellar
Polymer
Flooding
Advanced
Water-
Flooding
Massive
Hydraulic
Fracturing
Chemical
Explosive
Fracturing
Figure 1. Enhanced recovery technologies considered in the current study.
Table 1. Types of Pollution and Resources Affected by EOR Activities
EOR Activity
Item
Waste Disposal Secondary Impacts
Injection Production (Solid and (Chemical Manufacturing*
Construction Operations Operations Brine) Refining, etc.j
Type of Pollution:
Air
Noise
Surface
Groundwater
Resource:
Land use
Water supply
Demography and
commerce
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Background
Analyses of various environmental
pollutants associated with enhanced oil
and gas recovery are very important in
light of the current global energy
situation and the favorable view of
these processes held by the Department
of Energy (DOE). Millions of dollars are
being dedicated to EOR/EGR research
and development and pilot field projects
to support enhanced technologies in
this field. Steam flood, steam soak, in-
situ combustion, and C02 injection
projects are already being pursued at a
commercial scale. As the push for
development of enhanced oil and gas
recovery technologies accelerates and
prices of competing oil and gas rise,
widespread commercialization could
occur within 5 years.
The number of enhanced oil and gas
recovery projects in the United States
has increased from 1970 to 1977. More
important, actual oil recovered has
increased greatly (from about 150,000
barrels per day in 1970 to about
373,000 barrels per day in 1977). In
terms of potential for combined expan-
sion, estimates show that the recovery
of oil from primary and secondary
operations will yield only slightly more
than 30% of the total oil in place. This
rate of return leaves 70% of the oil
remaining in place, of which slightly
more than half can be recovered by
EOR. Thus about 30% of the original oil
in place becomes the target for enhanced
oil recovery operations.
Recovery Technologies
Considered
Two of the nine enhanced recovery
technologies (steam drive and in-situ
combustion) fall into the general
category of thermal enhancement,
wherein heavy, viscous oil is heated to
approximately 300° to 400° F to reduce
the viscosity and induce the oil to flow.
Four others (micellar polymer flooding,
advanced water flooding, CO2 miscible
flooding, and alkaline flooding) involve
the injection of chemical solutions into
the reservoir in combination with slug4
of water injected under pressure to alte"
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the fluid dynamics of the reservoir and
cause oil to be swept by the injected
water. Chemical explosive fracturing
and massive hydraulic fracturing involve
the use of water under pressure or
chemical explosion to cause fracture
networks in certain types of gas-bearing
formations. The fracturing affects
formation permeability, which is one
variable controlling the rate of gas flow
out of the formation. The final enhanced
recovery technology, directional drilling,
involves the oblique placement of well
bores to cross natural fracturing zones
and increase the surface area of the
well to augment gas production.
Pollution Potential of Recovery
Operations
Each of these nine technologies
involves a number of steps during which
environmental contamination can occur.
The technologies involve implementa-
tion of methods tested in laboratories
with small samples of natural geologic
formations or similar material (such as
packed sand). Thus considerable uncer-
tainty exists as to how injected fluids
will mix with reservoir fluids and travel
in the subsurface stratum as a whole.
This uncertainty is mainly because of
the known heterogeneity of underground
reservoirs and the limited knowledge of
reservoir boundaries. Further uncer-
tainty as to the nature and movement of
EOR pollutants is caused by the possi-
bility of various reactions between
injected fluids and formation pore
waters or chemical degradation products.
Because of the sketchy nature of
subsurface data, predicting whether
chemicals will move out of the reservoir
into the groundwater environment is
impossible.
Within the context of these uncer-
tainties, this report identifies types of
environmental degradation that may
occur and analyzes the various catego-
ries of pollutant discharges possible
with EOR and EGR. A preliminary
determination has been made of pollu-
tants that (1) generally do not appear to
exceed environmental regulations, (2)
clearly present an environmental prob-
lem, and (3) must be further researched
before an assessment can be made.
Particular attention is paid to air
emissions, surface water discharges,
water escaping into the groundwater
regime, noise pollution, geological
hazards, water consumption, secondary
impacts associated with increased
demands for certain classes of chemicals,
and socioeconomic changes.
Study Priorities
This study found that the top three
priorities of any further pollution
assessment of enhanced oil and gas
recovery should be: (1) the question of
subsurface pollution of water resources,
with emphasis on pollutant concentra-
tions and pathways, (2) an evaluation of
the toxicology of EOR and EGR chemi-
cals, and (3) an economic and techno-
logical analysis of dir pollution controls
for steam drive operations, since
thermal technologies are expected to
provide more than half of future EOR
production in the short term.
Project Approach
This study has attacked a complex
series of environmental questions in a
1-year program. Data have been re-
stricted to those available in the
literature and from agencies and firms
actively working in enhanced recovery.
The following discussion addresses
issues of scale (present pilot programs
versus future commercial-scale pro-
grams), data assembly, and data
analysis.
The Scaling Issue
Current enhanced recovery activities
(except for steam soak, in-situ
combustion, and C02 flooding) exist in
the field with only small pilot-scale
projects. The operating parameters and
environmental data that characterize
these pilot projects cannot always be
easily scaled up to commercial size.
Data have been developed based on
existing technology. Also, general
principles for determining how
environmental residuals may change as
operations are scaled to commercial
size are discussed, but they are not
included in projections because of
uncertainties.
Data Assembly
Evaluating the impacts of enhanced
recovery on the environment requires a
wide variety of data. This study has
addressed the data-gathering problem
as follows:
1. The open literature and govern-
ment research literature were
searched from 1970 to early 1979.
2. References cited in the above
documents were obtained.
3. A data base was developed to
characterize operating parameters
of the enhanced recovery projects
partially funded by DOE.
4. Additional data for selected pro-
jects cosponsored by DOE were
obtained from that agency and
from industry.
5. Selected state officials from Cali-
fornia, Texas, Oklahoma, and
West Virginia supplied information
on state regulations.
6. Specialists were used to develop
certain types of data from the
general literature (toxicity/car-
cinogenicity data and air emission
controls).
Data Analysis
In addition to assembly and use of
data from the above sources, consider-
able evaluation and analysis of unpub-
lished and published material played an
important role in the project. Analytical
methodology for impact assessment
was developed separately for each of
the nine enhanced recovery processes
in light.of the EOR/EGR activities, type
of pollution, and affected resources (see
Table 1). Typical process flow sheets
incorporating technology elements,
waste disposal activities, and environ-
mental concerns were prepared for
each process. Examples of process flow
sheets are shown in Figures 2 and 3 for
forward in-situ combustion and ad-
vanced hydraulic fracturing. The envi-
ronmental concerns are both above and
below ground. Such representations
can help determine pollution hazards,
but the probability of occurrence for
each pollutant scenario is different and
obviously site-specific.
The full report contains detailed
discussions on identification of envi-
ronmental impacts on surface water,
groundwater, air, and noise. Pollution
control technologies and options are
also discussed.
Results and Conclusions
The results and conclusions are
combined here to enumerate the
environmental concerns identified by
the study.
Clearly Identified
Environmental Problems
The following types of environmental
degradation do or may potentially occur
as a result of enhanced oil and gas
recovery activity. They need to be
studied further in terms of U.S. Environ-
mental Protection Agency (EPA) and
DOE policies on regulation, monitoring,
and research.
-------
Erosion,
Soil Loss,
Aesthetics
Blowout
Groundwater
Contamination
Construct
New Wells
Slurry.
Solid
Waste
Emitted
Gases
Condensers,
Scrubbers
Pipelines
or Tanks
Fugitive
Emissions
I Well Casing \
I
| Well Casing
Leaks to
Groundwater
or Surface
I I
I Burned .Burning Oil,
\ 7nno • 7nnt* I /? *i
I I
Subsurface
Transport
to Ground-
Technology Element, Subsurface
Technology Element. Above Ground
Environmental Concern
Waste Disposal Activities
Process Flow
Fluid Flow
Figure 2. Typical EOR process flow sheet for forward in-situ combustion.
4
-------
Freshwater
Supply
Erosion,
Soil Loss,
Aesthetics
Foaming Agent.
Polymers,
Biocides
v_x
Pressurized
Injection
Construct
Wells
Contamination
or Interruption
of Nearby
Wells
' Water Forced
into Gas Bearing
I Shales I
New Fracture
Systems
Formed
Contamination
of Coal Seams
Reclaim Water
by Natural
Pressure or
Mechanical
Sponging
r
—i
I
O
o
Technology Element, Subsurface
Technology Element, Above Ground
Environmental Concern
Waste Disposal Activities
Figure 3. Typical EGR process flow sheet for advanced hydraulic fracturing.
Process Flow
Optional Recycling
Flu id/Gas Flow
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Air Emissions from Steam
Generators
In general, SO*, NOX, H2S, and
particulate levels are of special concern.
Burning of locally available high-sulfur
oil results in high SOX emissions or the
economic penalties of using scrubbers.
Also, fugitive emissions of gases are
generated within the reservoir as a
result of the high temparatures of the
thermal recovery operation.
Water Availability
Most enhanced recovery technologies
require the use of significant quantities
of fresh water. In many areas this
presents a problem, since enhanced
recovery water needs conflict with other
water uses. The reuse of produced
water in injection processes and the
development of EOR chemicals compat-
ible with waters high in salt or cation
concentrations decrease the need for-
fresh water.
Disposal of Produced Brines and
Produced Hazardous Solutions
Large quantities of brines and chemi-
cally complex produced waters result
from,enhanced recovery operations.
Surface disposal, ocean disposal,
reinjection into the producing reservoir,
or disposal into another brine formation
are used. There is reason to suspect the
presence of metals and other hazardous
materials in the brine.
Disposal of Enhanced Gas
Recovery Fracturing Wastewater
Waters presently used in massive
hydraulic fracturing and other fluid-
fracturing methods are disposed of in
evaporative surface holding pits. The
dry residue containing potentially
hazardous materials may leach into
groundwater supplies.
Erosion Control
Active enhanced recovery sites involve
the continual construction of new
pipelines, wellheads, injectors, and
roadways. All of these activities can be
potentially serious erosion generators.
Of particular concern are fields in hilly
areas with clayey soils.
Spill Control
The variety of fluids being handled at
enanced recovery sites creates great
potential for spills. EPA spill prevention
guidelines must be closely adhered to
for all enhanced recovery projects.
Surface Effluents
Various small-scale surface effluents
such as scrubber water, waste oil,
cooling water, and produced emulsions
often contain hazardous substances
that may lead to surface and ground-
water contamination.
Noise from Construction and
Drilling Activity
During the short-term construction
and drilling phases of enhanced recovery
projects, activities must be developed
under an integrated plan to maintain
acceptable noise levels for workers (a
responsibility of the Occupational
Safety and Health Administration
(OSHA)) and neighboring communities
(an EPA concern).
Current Level of Environmental
Controls
Little attention has been paid to
environmental controls for EOR except
for thermal enhancement in the Kern
River field. Kern County, California. This
situation does not represent lack of
attention or negligence, since most
current projects are test or pilot
programs exempted from strict con-
formance with environmental regula-
tions. Several of the projects cospon-
sored by DOE have involved considerable
attention to environmental matters
(including the Long Beach and Coalinga
projects). The following controls are in
general use currently.
• Emissions from steam-soak gen-
erators in California are controlled
as mandated by the California Air
Resources Board (CARB). Current
controls include scrubbers for SOX
and vapor traps for hydrocarbons in
nonattainment areas. NOX control
strategies are currently under
debate.
• Spill control precautions such as
diking are probably followed at
about half of the sites.
• Most produced waters and other
liquid wastes are reinjected into
the producing formation.
• Erosion controls are followed at
about 10% at 20% of the sites.
• Attention is paid to workovers and
old well cementing before nearly
all projects.
• Drilling muds and EGR liquids are
disposed of in unliped evaporation
ponds. Residues are graded over.
• Water reuse is being tried on a pilot
scale.
• Minimal water monitoring iscarried
out.
• Extensive air monitoring is carried
out in California.
Pollutant Sources of No
Concern to Enhanced Recovery
Operation
A number of the potential pollutant
sources associated with recovery oper-
ations are probably not significant
enough to require industrywide control
measures or practices. Two such
sources are discussed here.
Noise from Routine Enhanced
Recovery Operations
EPA is generally concerned with
noise impacts on the general population.
Noise generated from injection activities
and well production activities in an
enhanced recovery operation generally
is not of a level to warrant EPA concern
off the site. Some of these activities may
be of concern with respect to industry
workers actually on the site, but these
are OSHA concerns and as such are
beyond the focus of this report.
Air Emissions from Enhanced
Recovery Technologies Other
Than Thermal Recovery
A variety of air pollution sources exist
in oil operations, including all of the
fossil-fuel-driven machinery (trucks,
pumps, generators, etc.). These sources
do not presently appear to be of
significant concern.
Unresolved Environmental
Issues
The unavailability of many critical
data precludes any firm conclusions
about the risk of enhanced recovery
operations in the areas of groundwater
seepage, health risks from chemicals,
secondary impacts from chemical
supply and manufacture, and degrada-
tion products.
Groundwater Seepage
Further information is required re-
garding the persistence of injected
chemicals over time, transport mech-
anisms out of reservoirs, and movement
of these chemicals in fresh-water
aquifers.
Health Risks from Chemicals
Most of the chemicals used in
enhanced recovery operations do n
appear on the various lists of chemicals
-------
that have been or are being studied by
EPA. Consequently, toxicological data
need to be developed for these chemicals.
Preliminary work is currently underway
by DOE.
Secondary Impacts Associated
with Chemical Supply and
Manufacture
Most of the chemical manufacturing
processes required to produce the
polymers, surfactants, and other chemi-
cals used in enhanced recovery do not
fall into the categories that have been
studied by the EPA effluent guideline
development document series. Further
analyses of these industries will be
valuable, since chemical demands wit)
be high with commercial-scale EOR
operations.
Degradation Products
The range of chemicals into which the
injected formulations may degrade in a
reservoir have not been studied in an
organized fashion. Depending on the
nature of the degradation products, the
scope of the water quality problems
associated with enhanced recovery may
be changed. Preliminary laboratory
investigations are under way at the DOE
Bartlesville Energy Technology Center.
Recommendations
Recommendations resulting from this
study fall into four categores: (1) im-
plementation of currently available
technology to deal with identified
environmental problems, (2) research to
develop effective control systems using
combinations of available technologies,
(3) development of monitoring programs
to provide information on discharges in
the vicinity of enhanced recovery
projects, and (4) more research on
environmental effects.
Implementation of Controls
Control of pollutant discharges and
cost-benefit analyses should be required
when pollutants have already been
demonstrated to constitute a problem
and when proven control methods exist.
Such pollutants include air and fugitive
emissions from steam drive and in-situ
technologies (SOX, H2S and volatile
organics in particular), hazardous
wastes resulting from waters injected
into wells, produced waters recycled to
reduce water consumption, and brines
at disposal sites.
Control Systems Research
The general needs are to develop
control systems and cost-benefit analyses
to deal with special problems in the
following areas: air emissions associated
with steam generation (SOX, NO*
problems), recycled produced waters
used as enhanced recovery injection
fluids, nonstructural controls as alter-
natives to technology-based control
devices, and hazardous waste degrada-
tion (composting, for example) for
ultimate disposal.
Environmental Monitoring
Specific procedures should be devel-
oped to monitor pollution abatement
efforts for steam drive and fugitive
emissions, construction and drilling
sources, EGR holding pit leachate and
wastewaters, heavy metals in brines,
hazardous organics and trace metals in
produced water, water quantities used
in EGR projects, and quantity and
quality of steam-drive scrubber water.
Environmental Effects
Research
A critical need exists for further
environmental research in the following
areas:
• Site-specific risk analysis for old
well casings in enhanced recovery
fields and for geological activity
resulting from EGR fluid dynamic
manipulation;
• Baseline data on groundwater
quality where injected waters
leave oil reservoirs;
• Site-specific flow models for sub-
surface groundwater to determine
the environmental impacts of
proposed projects;
• Chemical degradation and sub-
surface movement pathways; and
• Toxicology of chemicals used in
enhanced recovery.
The full report was submitted in
fulfillment of Contract No. 68-03-2648
by Rockwell International, Environ-
mental Monitoring and Services Center,
Newbury Park, California, under spon-
sorship of the U.S. Environmental
Protection Agency.
Ron Beck, Robert Shore, Terry Ann Scnven, and Melmda Lindquist are with
ERCO/Energy Resources Co., Inc., Cambridge, MA 02138
John S. Farlow is the EPA Project Officer (see below)
The complete report, entitled "Potential Environmental Problems of Enhanced
Oil and Gas Recovery Techniques,'' (Order No. PB 81 -240 186; Cost: $21.50.
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at'
Oil and Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison. NJ 08837
•fy US GOVERNMENT PRINTING OFFICE. 1981 -757-012/7344
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