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Water: Oil & Gas Extraction

Unconventional Extraction in the Oil and Gas Industry

Photo of a shale gas well pad

EPA is developing a proposed rule to amend the Effluent Limitations Guidelines (ELGs) for the Oil and Gas Extraction Category, (40 CFR Part 435). The proposed rule is scheduled for publication in 2014.

Background

EPA published a report on the coalbed methane extraction industry as part of its 2010 ELG plan. In the plan, EPA also announced that it was initiating two separate rulemakings to revise Part 435 to address discharges from coalbed methane and from shale gas extraction. The Agency had decided that separate rulemaking actions were appropriate for two main reasons: 1) shale gas is extracted primarily through a combination of horizontal drilling and hydraulic fracturing and coalbed methane extraction does not utilize horizontal drilling and entails a much smaller degree of fracturing; and 2) EPA was further ahead in its data collection activities for coalbed methane than for shale gas extraction.

Since 2010, EPA learned that the economics of extracting oil and gas from one source are intrinsically linked with the economics of extraction from other available sources. For example, increased shale gas production over the last year led to an overabundance of supply, which led to a decrease in gas prices that not only affects shale gas extraction but also coalbed methane. The result is that much of the data EPA previously collected for coalbed methane are outdated. The Agency is still examining a variety of options including separate rulemakings or a combined rulemaking.

Gas Extraction Process

Recent advances in hydraulic fracturing and horizontal drilling have made extraction of natural gas from unconventional resources more technologically and economically feasible. Hydraulic fracturing is used to extract natural gas from highly impermeable rock formations, such as shale rock, by injecting large amounts of fracturing fluids at high pressures to create a network of fissures in the rock formations and provide the natural gas a pathway to travel to the well for extraction. Geologic pressure within the impermeable shale formations force these fracturing fluids back to the surface (sometimes referred to as "flowback water"), along with naturally occurring formation water (referred to as "produced water"). These wastewaters are collectively referred to as "shale gas extraction wastewater."

An additional source of unconventional gas is coalbed methane. This source of gas is naturally created during the geologic process of converting plant material to coal ("coalification"). To extract the methane, coalbed methane operators drill wells into coal seams and pump out ground water (produced water). Removing the ground water from the formation is necessary to produce coalbed methane, as the water removal reduces the pressure and allows the methane to release from the coal to produce flowing natural gas.

Wastewater Generated by Unconventional Extraction

Wastewater from unconventional oil and gas wells often contain high concentrations of total dissolved solids (salts). Shale gas extraction wastewater may also contain various organic chemicals, inorganic chemicals, metals, and naturally occurring radioactive materials (NORM). Produced water pumped out of coalbed methane wells may include pollutants such as chloride, sodium, sulfate, bicarbonate, fluoride, iron, barium, magnesium, ammonia, and arsenic. The quantity and quality of flowback and produced waters from both shale gas and coal bed methane varies from basin to basin, and over the lifetime of a well.

Current Federal Regulatory Framework

Direct discharges from unconventional oil and gas extraction are subject to NPDES permit regulations (40 CFR Parts 122 through 125). Indirect discharges to Publicly Owned Treatment Works (POTWs) are subject to the General Pretreatment Regulations (40 CFR Part 403). 

NPDES permits must include technology based effluent limitations. For direct dischargers of unconventional oil and gas wastewaters from onshore oil and gas facilities – with the exception of coalbed methane – technology-based limitations are based on the Effluent Limitations Guidelines (ELGs) for the Oil and Gas Extraction Category (40 CFR Part 435). Permits for onshore oil and gas facilities must include the requirements in Part 435, including a ban on the discharge of pollutants, except for wastewater that is of good enough quality for use in agricultural and wildlife propagation for those onshore facilities located in the continental United States and west of the 98th meridian. Part 435 does not currently include categorical pretreatment standards for indirect discharges to POTWs for wells located onshore (i.e., PSES or PSNS).

Direct discharges from coalbed methane extraction from onshore oil and gas facilities are not currently subject to limitations under Part 435, as EPA did not consider such discharges in developing the onshore oil and gas ELG. NPDES permits for coalbed methane discharges are currently developed according to the best professional judgement (BPJ) of the permit authority, based on the factors specified in 40 CFR 125.3(c)(2). The BPJ-based requirements that have been applied to disposal of coal bed methane wastewater vary significantly from state to state, ranging from limitations on some conventional pollutants prior to discharge, to prohibition of direct discharges to waters of the U.S. (For more information on the BPJ permit process, see Chapter 5 of the NPDES Permit Writer's Manual).

Additional Resources

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Additional Information

To obtain more information on the rulemaking please contact Lisa Biddle, (biddle.lisa@epa.gov) at 202-566-0350.

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