U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2014–3104

November 2014

Integrated Research by the Energy and Minerals and the Environmental Health Mission Areas

USGS Investigations of Water Produced During Hydrocarbon 

Reservoir Development

Introduction 

Significant quantities of water are present in hydrocarbon 

reservoirs. When brought to the land surface during oil, gas, and 

coalbed methane production, the water—either naturally occurring 

or injected as a method to enhance production—is termed produced 

water. (See sidebar, Definitions of selected terms, next page.) 

Produced water is currently managed through processes such as 

recycling, treatment and discharge, spreading on roads, evaporation or infiltration, and deep well injection. U.S. Geological 

Survey (USGS) scientists conduct research and publish data 

related to produced water, thus providing information and insight 

to scientists, decisionmakers, the energy industry, and the public. 

The information advances scientific knowledge, informs resource 

management decisions, and facilitates environmental protection. 

This fact sheet discusses integrated research being conducted by 

USGS scientists supported by programs in the Energy and Minerals 

and Environmental Health Mission Areas. The research products 

help inform decisions pertaining to understanding the nature and 

management of produced water in the United States.

In conventional oil and gas wells, produced water generally consists of naturally occurring brine present in the reservoir 

and water injected nearby to push the hydrocarbon deposit into 

production wells (water flooding). Alternatively, for continuous or 

unconventional resources, such as shale gas or tight oil, fracturing 

fluid and a solid material (proppant) are injected into the reservoir 

under very high pressure in order to create fractures to increase 

rock porosity and permeability. In this scenario the produced water 

is usually a mixture of the injected fluids with formation brines in 

the reservoir. The quality of produced water is variable, ranging 

in salinity from similar to that of drinking water to several times 

more saline than sea water. Various constituents can be contained 

in produced water from petroleum or coal reservoirs, including 

dissolved salt, petroleum and other organic compounds, suspended 

solids, trace elements, bacteria, naturally occurring radioactive 

materials (NORM), and anything injected into the well (Clark 

and Veil, 2009). Because of the considerable variability in water 

chemistry and the potentially large volumes involved, the management of produced water is an important and complex issue.

Using 2007 data, Clark and Veil (2009) estimated that 

hydrocarbon production in the United States generated 57.4 million 

barrels of water per day (1 barrel (bbl)=42 gallons). Since then, 

a rapid increase in hydrocarbon production across the United 

States, particularly for shale gas, tight gas, tight oil, and coalbed 

methane, has led to a commensurate increase in produced water 

volumes. In Pennsylvania, for example, natural gas production 

increased from 0.20 trillion cubic feet in 2006 to 2.26 trillion 

cubic feet in 2012, primarily due to the production of natural 

gas from the Marcellus Shale (Pennsylvania Department of 

Environmental Protection, 2013). During this same period, the 

annual amount of produced water in Pennsylvania increased from 

6.6 million bbl to 24.4 million bbl. The Bakken reservoir in the 

Williston Basin in Montana, North Dakota, South Dakota, and 

Saskatchewan is another area of recent and dramatic increased 

hydrocarbon production (graph) wherein management plans for 

produced water are being developed. The dramatic increase in 

hydrocarbon reservoir development and the corresponding rise in 

the volume of associated produced water has taken place in areas 

of the United States that have not previously seen such intense 

development. The rapid expansion of energy resource extraction 

has the potential to overwhelm local infrastructure and strain many 

parts of the produced water cycle, including the storage, treatment, 

reuse, transportation, or disposal of these waters. 

A layer of oil (top) 

and produced water 

(bottom) separating 

from one another 

after being collected 

from an oil well in 

the Permian Basin, 

Texas. Photograph 

by Francisco Reyes, 

USGS. 

Oil production from the Bakken Formation 

showing the increase in the number of producing 

wells. Data provided by Department of Natural 

Resources, North Dakota Industrial Commission. 

1996 2000 2004 2008 2012

Year

0

200,000

400,000

600,000

800,000

1,000,000

Daily oil production, in barrels

Oil production

0

2,000

4,000

6,000

8,000

Producing

Number of producing wells

wells
Definitions of selected terms

flowback water During the development of unconventional resources such as shale gas or tight oil, a fracturing fluid and a proppant

are injected into the reservoir under high pressure in order to create fractures to increase rock porosity and permeability. Flowback 

water consists primarily of the injected water and is generated in the first few days to weeks following hydraulic fracturing. 

formation brine or water Naturally occurring water, typically of brackish to brine salinity, which is present in oil and gas 

reservoirs. Formation water in many coalbed methane reservoirs is relatively fresh.

produced water Any water produced from a hydrocarbon well, including flowback water, formation water, injected fluids, 

water condensing from the gas phase, and mixtures thereof (also referred to as co-produced water).

conventional hydrocarbon resource A relatively high permeability oil and (or) gas accumulation with a distinct waterhydrocarbon boundary.

unconventional hydrocarbon resource A continuous hydrocarbon accumulation, typically in a low permeability reservoir, 

which lacks a distinct hydrocarbon-water contact and often covers a substantial area. Examples include shale gas, tight gas,

tight oil, and coalbed methane reservoirs.

Management of Produced Water

Nationally, more than 95 percent of produced water from 

hydrocarbon resource development is disposed of by injection, 

either into special (Class II: Associated with oil and gas production) 

underground injection control wells or into petroleum wells to 

enhance recovery or to maintain reservoir pressure (Clark and 

Veil, 2009). The proportionally small remainder that is not injected 

is either treated and disposed of in the surface environment, 

beneficially utilized, or recycled for use in hydraulic fracturing 

or other oil and gas operations. Lower salinity and better quality 

co-produced waters, which are often treated in some way, have 

many uses, including for irrigation, water for livestock, ecosystem 

and habitat maintenance, and aquaculture. Other known uses 

include road spreading for dust control and deicing, fire control, 

water for drilling mud, and water for cooling or other processes in 

electrical power generation and other industrial activities. While 

safeguards are typically included in environmental regulations, 

unintended consequences (both positive and negative) can result 

from the beneficial uses of produced water. 

Beneficial Uses of Produced Water 

The water and salt that make up brine in sedimentary basin 

formations have been of interest to the oil and gas industry for 

more than 100 years. In some areas of the country, salts and other 

constituents in the brine historically have been, and in some cases 

currently are, of significant economic value. For instance, iodide 

recovered from produced water in Oklahoma is the largest source 

of iodine in the United States (Polyak, 2013). Produced water 

can be treated and recycled, particularly in arid environments, for 

agricultural uses in crop production and livestock management. 

Increasingly, produced water is used to enhance the production of 

hydrocarbons; waterflooding and hydraulic fracturing are used in 

the development of unconventional resources. 

Potential Environmental Concerns 

The infrastructure used to store and transport produced water 

can fail, resulting in spills, leaks, and other environmental releases. 

Legacy oil and gas operations, including improperly abandoned or 

poorly cemented wells, could potentially serve as conduits for deep 

subsurface fluids to move into shallow freshwater systems. Disposal 

procedures (primarily historical) for produced water in evaporation pits can impact shallow groundwater. The deep injection of 

produced water can produce earthquakes, and the water can affect 

shallow water by migrating through improperly abandoned wells. 

The first USGS multidisciplinary investigation to study the 

impacts of produced water was conducted from 2001 to 2006 

at Skiatook Lake in the southeastern part of the Osage Indian 

Reservation in northeastern Oklahoma. The study focused on 

determining the fate of produced water and the effects of produced 

water disposal on the near-surface environment (Herkelrath and 

others, 2007; Kharaka and others, 2007). Results from the investigation (http://toxics.usgs.gov/sites/produced_water/) helped 

provide information that environmental officials, land managers, 

petroleum companies, and land owners need to assess human and 

ecosystem impacts and to develop risk-based corrective actions to 

clean up contamination from produced water. 

Mapping Brine Contamination and Geochemical Fingerprinting

Borehole, ground, and airborne geophysical survey methods 

have been used by the USGS to characterize and map the nearsurface and subsurface distribution of produced water and its 

hydrogeologic setting. USGS studies have examined the radionuclide 

content of produced water and have used geophysical methods to 

map surface radiometric variations. Additional studies mapped 

electrical property variations because the electrical conductivity of 

water increases in direct proportion to increases in total dissolved 

solids. Airborne electromagnetic (AEM) surveys were first used to 

map the contamination of shallow groundwater (less than 300 feet 

below ground surface) resulting from the disposal of salineproduced water at oil fields. Research at the East Poplar oil field in 

northeastern Montana (Thamke and Smith, 2014) has related the 

variations in subsurface electrical conductivity, interpreted from an 

AEM survey, to groundwater models, improving the ability to predict 

the movement of a hidden, underground saline water plume, several 

miles in aerial extent, caused by the failure of an injection well.

Geochemical tools, such as chemically fingerprinting 

produced water from specific reservoirs, help identify potential 

sources of contaminants in the surface environment (such as 

chloride in soil, groundwater, and lakes). Produced water frequently 

exhibits characteristic ratios of sodium to bromine and chlorine to 

bromine, which are useful in determining the primary source of their 

salinity. USGS scientists have used this method to determine the 

source of salts in produced water from the Marcellus Shale gas wells 

in Pennsylvania (Engle and Rowan, 2014). Isotopes (molecules with 

the same number of protons but different numbers of neutrons; for 
instance, oxygen-18 versus oxygen-16) are another important tool 

that has been used to differentiate water from different reservoirs. 

Using ratios of strontium-87 (radiogenic) to strontium-86 (stable) 

and radium-228 to radium-226 (both radiogenic), USGS scientists 

are able to distinguish otherwise nearly identical water produced 

from different reservoirs (Rowan and others, 2011).

Characterization 

Information on water quality and physical parameters provides 

context for potential environmental impacts, as well as providing 

industry with base-level information about use. One source of 

such data is the USGS Produced Waters Geochemical Database 

(Blondes and others, 2014), which provides data for more than 

160,000 produced water samples, including samples from shale gas, 

tight oil, and coalbed methane wells. A broad array of information, 

such as the potential mineral value, viability of disposal options, 

potential for mineral scale, and possible environmental risks can be 

gleaned from such basic data. For instance, data in table 1 indicate 

substantial differences in produced water composition from a coalbed 

methane well in Wyoming, a conventional oil well in Ohio, and 

a shale gas well in Pennsylvania. Despite this new dataset, important data gaps still exist. To address this issue, the USGS continues 

to actively characterize produced water samples in areas of critical 

need, including the Appalachian, Permian, and Williston Basins. 

Scientists have also begun studying microorganisms in 

produced water, from both environmental and resource perspectives. 

For example, the presence of hydrogen sulfide-producing bacteria 

could negatively impact the success of gas extraction; souring of 

wells and the corrosion of drilling equipment are two well-known 

problems caused by hydrogen sulfide produced in the reservoir or 

well bore by bacteria as a byproduct of their metabolic processes. 

On the other hand, microorganisms could be used to enhance 

natural gas production or to mitigate potential contaminants. In 

recent investigations, USGS scientists studied microbial populations in produced water from shale gas production in northern 

Pennsylvania. Additional efforts to characterize microorganisms 

in produced water are being carried out in unison with sampling 

efforts to characterize chemical and physical properties.

Research Activities Inform Management Decisions 

An example of USGS and industry collaboration includes 

investigating the results of beneficial uses for produced water from 

coalbed methane wells in the Powder River Basin of Wyoming 

and Montana. The produced water in the basin generally is of 

relatively low salinity, but it contains high levels of sodium, which 

poses a possible threat to soil quality. USGS scientists, working in 

conjunction with the U.S. Department of Energy’s National Energy 

Technology Laboratory and an industry collaborator, examined the 

potential impacts of using such water in a subsurface drip irrigation 

system. In this system, treated coalbed-methane water was injected 

about 3 feet below the ground surface to support the growth of 

forage crops (Engle and others, 2011; Bern and others, 2013; Sams 

and others, 2014). Using geophysical and geochemical techniques, 

the water and solutes in the system were tracked. Results from 

this investigation suggest that calcium release from the continued 

dissolution of the nearly ubiquitous mineral gypsum (CaSO4

∙2H2O) 

inhibits sodium accumulation from reaching deleterious levels in 

soil. Findings from this work are helping operators understand the 

need to track gypsum content in soil to better manage subsurface 

drip irrigation systems that utilize coalbed methane-produced water.

Table 1. Chemical data for selected constituents from three 

produced water samples in the National Produced Waters Geochemical 

Database. Data reported in units of milligrams per liter of fluid.

[National Produced Waters Geochemical Database, http://energy.usgs.gov/

EnvironmentalAspects/EnvironmentalAspectsofEnergyProductionandUse/

ProducedWaters.aspx#3822349-data]

Constituent

Conventional

oil well

in Ohio

Coalbed

methane well

in Wyoming

Shale gas

well in

Pennsylvania

Total dissolved 

solids

472,000 1,020 186,000

Barium Not reported 19.5 13,600

Bicarbonate Not reported 487 57.1

Bromide 1,580 38.9 872

Calcium 42,800 337 11,200

Chloride 292,000 12.0 98,300

Iodide 17.9 Not reported Not reported

Magnesium 8,350 10.0 858

Sodium 122,000 110 39,100

Strontium 736 9.7 3,580

Sulfate Not reported Below

detection limit

50.0

Cultures of hydrogen sulfide-producing bacteria enriched from 

shale gas-produced waters. The black color denotes the presence 

of insoluble iron sulfide minerals, an indicator of bacterial sulfide 

production. The clear culture on the right is an uninoculated control 

sample. Photograph by Darren Dunlap, USGS. 

USGS employee downloading soil moisture data at a subsurface drip 

irrigation site utilizing coalbed methane-produced water to grow the 

surrounding alfalfa, Johnson County, Wyoming. Photograph by 

Bruce Engle, USGS volunteer. 
In oil- and gas-bearing States of the northern and northeastern United States (such as Michigan, Ohio, Pennsylvania, and 

New York), spreading relatively saline produced waters on roads has 

been a method used for decades to provide dust suppression on dirt 

roads during warmer months and deicing of paved roads during the 

winter. Although the most concentrated solutes in produced waters 

from this region (that is, sodium, calcium, and chloride) are relatively benign, there is a possibility that trace constituents can accumulate in areas of road spreading. For example, characterization 

studies by Rowan and others (2011) show that the radium content 

of produced water from Pennsylvania and New York is geologically

anomalous. Radium derived from the decay of uranium and thorium 

in the reservoir rocks is a radioactive element found in many 

produced waters. Because radium has an affinity for fine sediments, 

such as clays, USGS scientists have begun collecting soil samples 

adjacent to areas of road spreading to determine if such an accumulation is occurring. Initial results have yielded limited evidence for 

radium accumulation in areas of road spreading (Skalak and others, 

2014). Such information is provided to the public to help allow for 

informed decisions pertaining to this beneficial use.

Outreach, Collaboration, and Future Directions

As changes occur in how petroleum resources are exploited or 

how produced water is used and disposed of, the USGS continues to 

track and modify research objectives and directions. For example, as 

production from shale-gas and tight-oil reservoirs have increased, the 

USGS has shifted its research to focus on produced water from those 

sources. To learn more about current and future research directions, as 

well as links to publications, data, and resources, visit these Web sites: 

Energy Resources Program—Produced Waters (http://energy.usgs.

gov/HealthEnvironment/EnergyProductionUse/ProducedWaters.aspx) 

and Environmental Health—Toxic Substances (http://toxics.usgs.gov/

highlights/ph20.html).

The research activities described in this fact sheet are conducted 

in collaboration with other USGS projects, including the “Brine 

Contamination to Prairie Potholes from Energy Development 

in the Williston Basin” project (http://steppe.cr.usgs.gov/); with 

other Federal agencies such as the Bureau of Reclamation and the 

U.S. Department of Energy; with State agencies, including water 

and oil and gas agencies; and with industry groups and hydrocarbon producers. 

References Cited

Bern, C.R., Boehlke, A.R., Engle, M.A., Geboy, N.J., Schroeder, K.T., 

Zupancic, J.W., 2013, Shallow groundwater and soil chemistry 

response to 3 years of subsurface drip irrigation using coalbedmethane-produced water: Hydrogeology Journal, v. 21, p. 1803–1820, 

http://dx.doi.org/10.1007/s10040-013-1058-0.

Blondes, M.S., Gans, K.D., Thordsen, J.J., Reidy, M.E., Thomas, Burt, 

Engle, M.A., Kharaka, Y.K., and Rowan, E.L., 2014, U.S. Geological 

Survey national produced waters geochemical database v2.0 (provisional): U.S. Geological Survey Web page accessed September 22, 2014, 

at http://energy.usgs.gov/EnvironmentalAspects/EnvironmentalAspectsof

EnergyProductionandUse/ProducedWaters.aspx#3822349-data. 

Clark, C.E, and Veil, J.A., 2009, Produced water volumes and 

management practices in the United States: Argonne National 

Laboratory Report ANL/EVS/R-09/1, 60 p.

Engle, M.A., Bern, C.R., Healy, R.W., Sams, J.I., Zupancic, J.W., and 

Schroeder, K.T., 2011, Tracking solutes and water from subsurface drip 

irrigation application of coalbed methane–produced waters, Powder 

River Basin, Wyoming: Environmental Geosciences, v. 18, p. 169 –187, 

http://dx.doi.org/10.1306/eg.03031111004. 

Engle, M.A., and Rowan, E.L., 2014, Geochemical evolution of produced 

waters from hydraulic fracturing of the Marcellus Shale, northern 

Appalachian Basin—A multivariate compositional data analysis 

approach: International Journal of Coal Geology, v. 126, p. 45 –56, 

http://dx.doi.org/10.1016/j.coal.2013.11.010.

Herkelrath, W.N., Kharaka, Y.K., Thordsen, J.J., and Abbott, M.M., 

2007, Hydrology and subsurface transport of oil-field brine at 

the U.S. Geological Survey OSPER site “A”, Osage County, 

Oklahoma: Applied Geochemistry, v. 22, no. 10, p. 2155–2163, 

http://dx.doi.org/10.1016/j.apgeochem.2007.04.004.

Kharaka, Y.K., Kakouros, Evangelos, Thordsen, J.J., Ambats, Gil, 

and Abbott, M.M., 2007, Fate and groundwater impacts of 

produced water releases at OSPER “B” site, Osage County, 

Oklahoma: Applied Geochemistry, v. 22, no. 10, p. 2164–2176, 

http://dx.doi.org/10.1016/j.apgeochem.2007.04.005.

Pennsylvania Department of Environmental Protection, 2013, 

Oil and gas reporting Web site, accessed June 27, 2013, at 

https://www.paoilandgasreporting.state.pa.us/publicreports/

Modules/Welcome/Welcome.aspx.

Polyak, D.E., 2013, Iodine: U.S. Geological Survey Minerals Yearbook 

2012, 6 p., accessed September 22, 2014, from http://minerals.usgs.gov/

minerals/pubs/commodity/iodine/index.html.

Rowan, E.L., Engle, M.A., Kirby, C.S., and Kraemer, T.F., 2011, 

Radium content of oil- and gas-field produced waters in the northern 

Appalachian Basin (USA)—Summary and discussion of data: U.S. 

Geological Survey Scientific Investigations Report 2011–5135, 31 p., 

http://pubs.usgs.gov/sir/2011/5135/.

Sams, J.I., Veloski, Garret, Smith, B.D., Minsley, B.J., Engle, M.A., 

Lipinski, B.A., Hammack, Richard, and Zupanicic, J.W., 2014, 

Application of near-surface geophysics as part of a hydrologic study 

of a subsurface drip irrigation system along the Powder River floodplain near Arvada, Wyoming: International Journal of Coal Geology, 

v. 126, p. 128–139, http://www.sciencedirect.com/science/article/pii/

S0166516213002413.

Skalak, K.J., Engle, M.A., Rowan, E.L., Jolly, G.D., Conko, K.M., 

Benthem, A.J., and Kraemer, T.F., 2014, Surface disposal of produced 

waters in western and southwestern Pennsylvania—Potential for accumulation of alkali-earth elements in sediments: International Journal 

of Coal Geology, v. 126, p. 162–170, http://www.sciencedirect.com/

science/article/pii/S0166516213002681.

Thamke, J.N., and Smith, B.D., 2014, Delineation of brine contamination

in and near the East Poplar oil field, Fort Peck Indian Reservation, 

northeastern Montana, 2004–09: U.S. Geological Survey Scientific 

Investigations Report 2014–5024, 40 p., http://dx.doi.org/10.3133/

sir20145024.

USGS scientists inspect a sediment core collected adjacent to an area 

of produced water road spreading, Crawford County, Pennsylvania. 

Photograph by Mark Engle, USGS. 

ISSN 2327– 6932 (online) By Mark A. Engle, Isabelle M. Cozzarelli, and Bruce D. Smith http://dx.doi.org/10.3133/fs20143104