GEOLOGICAL SURVEY OF ALABAMA
Water Management Strategies for Improved
Coalbed Methane Production in the
Black Warrior Basin
Funded by the
Under Award DE-FE0000888
Project Duration: 10/1/2009-9/30/2012
Large volumes of formation water need to be produced to recover natural gas from coal, which is a natural resource that is critical to Alabama’s economy and energy security. Accordingly, management of produced water is one of the most critical issues facing the coalbed methane (CBM) industry. The Black Warrior basin of Alabama (fig. 1) is a mature province where CBM producers face a range of water management issues. In the eastern CBM fields, fresh water has been disposed safely in streams for decades. Even so, this practice is a subject of increasing scrutiny by environmental groups and agencies, and some of the produced water may have beneficial agricultural and industrial uses. In some fields, where significant potential exists for expansion of the CBM industry, saline formation water limits the ability of producers to pump wells to depressurize coal, which in turn leads to underperforming gas production.
Figure 1.—Generalized map showing coalbed methane fields in Alabama and the distribution of
fresh and saline formation water.
The Black Warrior basin is a cradle of the modern CBM industry that has provided a wealth of experience and has guided CBM development around the globe. More than 2.1 trillion cubic feet of coalbed gas has been produced from the basin, and 4,869 wells are active in 20 CBM fields (fig. 1). Annual gas production has been between 105 and 121 billion cubic feet since 1993 (fig. 2), and although the basin is considered mature, exploration and drilling operations are highly active. Cumulative water production now exceeds 1,340 million barrels, and annual production was higher than 78 million barrels in 2007. Water production has been rising since 2001 in response to renewed expansion of the CBM industry in Alabama, and so water management issues continue to be of high concern.
Figure 2.—History of gas and water production from coalbed methane reservoirs in the Black Warrior basin.
Note that water production has been increasing steadily since 2001.
Water composition varies greatly and influences how produced water can be managed. Indeed, CBM is considered to be largely a hydrodynamic natural gas play, thus understanding basin hydrology is essential for developing a viable strategy for exploration and reservoir management. In-stream disposal of produced water is the dominant practice in the basin. Underground injection has in the past augmented in-stream disposal where produced water is highly saline. Much of the produced water has total dissolve solids (TDS) content lower than 3,000 mg/L and can potentially be put to beneficial use within and outside the CBM industry. With minimal processing, much of this water may be used for a spectrum of industrial and agricultural purposes. Moreover, intense drought in the southeastern U.S. over the past decade has created a need for new water supplies.
To assist the CBM industry, the Geological Survey of Alabama is conducting a three-year study that provides a conceptual framework for the management of produced water from coal. This study will employ an integrated, life-cycle approach that draws on a spectrum of geologic disciplines (fig. 3). This investigation employs a spectrum of geologic, hydrologic, geochemical, petrologic, GIS, and other computational techniques to characterize the reservoir geology and basin hydrology of the Black Warrior basin to develop new water management strategies that ensure environmental protection, foster beneficial use of produced waters, and improve reservoir performance.
Figure 3.—Conceptual framework outlining proposed study of the relationships among reservoir geology,
basin hydrology, and water management strategies in coalbed methane reservoirs.
Jack Pashin, Principal Investigator (Stratigraphy, Structure)
Richard Carroll (Organic petrology)
Guohai Jin (Structural Geology, Software Development)
David Kopaska-Merkel (Sedimentary Petrology)
Marcella McIntyre (Structural Geology, Hydrogeology)
Mac Mckinney (Hydrogeology)
This project includes a vigorous technology transfer program that is designed to facilitate the implementation of water management strategies in CBM reservoirs. Results are being presented at technical meetings and workshops and are being published in technical journals and meeting proceedings. This website is central to technology transfer activities, and links to relevant reports and materials are given below:
Groshong, R. H., Jr., Pashin, J. C., McIntyre, M. R., 2009, Structural controls on fractured coal reservoirs in the southern Appalachian Black Warrior foreland basin: Journal of Structural Geology, v. 31, p. 874-886. (Link)
Pashin, J. C., 2010, Variable gas saturation in coalbed methane reservoirs of the Black Warrior Basin: Implications for exploration and production: International Journal of Coal Geology, in press. (Link)
Pashin, J. C., 2007, Hydrodynamics of coalbed methane reservoirs in the Black Warrior Basin: key to understanding reservoir performance and environmental issues: Applied Geochemistry, v. 22, p. 2257-2272. (Link)
Pashin, J. C., and McIntyre, M. R., 2003, Temperature-pressure conditions in coalbed methane reservoirs of the Black Warrior basin, Alabama, U.S.A: implications for carbon sequestration and enhanced coalbed methane recovery: International Journal of Coal Geology, v. 54, p. 167-183. (Link)
Pitman, J. K., Pashin, J. C., Hatch, J. R., and Goldhaber, M. B., 2003, Origin of minerals in joint and cleat systems of the Pottsville Formation, Black Warrior basin, Alabama: implications for coalbed methane generation and production: American Association of Petroleum Geologists Bulletin, v. 87, p. 713-731. (Link)
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