Characteristics of Coalbed Methane Produced Water in

Alabama

Nick TewAlabama State Geologist/Oil and Gas Board Supervisor

Geological Survey of AlabamaState Oil and Gas Board of Alabama

Atlantic CouncilFossil Fuel Produced Water Workshop

Washington, DCJune 24-25, 2013

Alabama’s Fossil Fuel Energy Endowment Coal

Black Warrior Basin Coal Measures Coastal Plain Lignite (low-rank coal)

Oil Conventional

SW Alabama Oil and Condensate Black Warrior Basin Oil

Unconventional Oil Sands of North Alabama Oil Shale of North Alabama

Natural Gas Conventional

SW Alabama Black Warrior Basin

Unconventional Coalbed Methane of Black Warrior Basin Paleozoic Gas Shales of North Alabama

Geology of Alabama

Significant Activity Areas

Coalbed Methane in Alabama

• Degasification experiments for mine safety began in the mid-1970s.

• Commercial production began in 1980.

• Currently close to 5,000 active wells in 20 fields.

• Annual gas production between 105 and 121 Bcf for the last 20 years.

• More than 2.1 Tcf cumulative gas production.

• More than 1.7 billion barrels of water produced.

Alabama CBM Fields

Cumulative Gas Production from 1980-

2009

Cumulative Water Production from 1980-2009

Cumulative Gas and WaterProduction

Development and Production

• Drilling and hydraulic fracturing currently uses “city” water

• Usually trucked to location

•Additional water during production is not needed

Co-Produced Water• CBM production is pressure driven and usually

requires dewatering of coals to lower hydrostatic pressure for gas production.

• Water production is generally high early in a well’s life and decreases rapidly.

• Gas production generally peaks in the first few years, after peak water, then decreases.

• High water production can limit how often and how much a well can be pumped, limiting gas production.

Peak Gas and WaterProduction

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Reese-Taurus-91-21-08-07-04 #1684(OGB PN 10009)

Monthly Production

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Co-Produced Water• As new areas of production come on line, water

production is relatively high.

• As an area reaches maturity, the water production will slow and level off.

• Some areas, with high recharge rates, will continue to produce significant water volumes over the life of the well.

• In and around mining, where water levels have been drawn down prior to drilling, wells produce little to no water.

Water production through time

Water production through time

Water Treatment and Disposal• In-stream disposal is the dominant practice in the Black

Warrior Basin.

• Prior to disposal, water is treated to remove silt, clay, iron, and manganese compounds.

• Underground injection can augment in-stream disposal in areas of highly saline water; however, currently all produced water is disposed of in-stream.

• Potential beneficial uses exist for produced water with less than 3,000 mg/L TDS.

• In the southwestern CBM fields, water is more saline and limits the ability to pump wells.

Produced WaterDischarge Points

Water Chemistry Major constituents:

Mostly sodium-chloride, some areas are dominated by sodium bicarbonate waters.

Generally low in sulfate, magnesium, and calcium.

Almost all wells exceed secondary drinking water standards for TDS (500 mg/L), but the average well is in a USDW (<10,000 mg/L).

Average levels of barium, cadmium, fluoride, lead, and thallium exceeds the drinking water MCL; average levels of zinc and manganese exceed the secondary drinking water regulations.

CBM Produced Water in Alabama

Potential Beneficial Uses: Aquaculture and irrigation water, in particular shrimp

farming Water for drilling and hydraulic fracturing Municipal supply

Alternative water treatment: Reverse osmosis systems Artificial wetlands (Clemson-Chevron research)

Alternative to in-stream disposal: SWD wells, however, no consistent high capacity zones

identified

Acknowledgments

GSA CBM Produced Water Project funded by the U.S. Dept. of Energy, Office of Fossil Energy, NETL, DOE Award Number DE-FE0000888.

GSA Research Team: Marcella McIntyre-Redden, Steve Mann, Jack Pashin (now at OK State), David Kopaska-Merkel, Ashley Williams, and Mac McKinney.