A Critical Look At the Geologic and Reservoir Controls on Producing Appalachian Basin Coalbed Methane

KUUSKRAA, VELLO; KELAFANT, JONATHAN, and KUUSKRAA, JASON A., Advanced Resources International, Inc.

In many respects, the Appalachian basin (central and northern) can be considered the birthplace of the coalbed methane (CBM) industry with gas production from coal seams dating back to the early 1920s. Additionally, Appalachian coal seams were the subject of much of the early CBM research performed by the U.S. Bureau of Mines and U.S. Department of Energy. However, despite the early research and a relatively large CBM resource base of about 66 Tcf, the basin has only recently begun to emerge as a significant producer. While ownership issues hampered the industry from growing during the mid-1980s, it was a lack of adequate reservoir characterization that has prevented the basin from reaching its full production potential.
The coal seams of the Appalachian basin possess distinctly different reservoir properties from those of other CBM producing basins such as the Warrior and San Juan basins. Failure to recognize these differences led companies to employ inappropriate completion and production technologies. For example, the early use of gelled stimulation fluids in the relatively "dry" Pocahontas coal seams caused serious formation damage and greatly impaired the performance of these wells. However, the steady growth in Virginia's CBM production demonstrates that as our knowledge of the reservoir properties increases, substantial portions of the basin's CBM resource base can be converted to reserves. This paper reviews the geologic and reservoir controls on Appalachian basin CBM production and relates these controls to the selection of appropriate completion and production technologies.

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