Powder River Basin, Wyoming: An Expanding Coalbed Methane (CBM) Play 

Abstract

Coalbed methane exploration in the Powder River basin represents an active play with considerable potential for future expansion and success. Such potential is related to the specific geology and character of the target coals, which exist in the Paleocene Fort Union Formation at depths of 300-2000 ft (91-610 m). Although of low rank (lignite-subbituminous), these coals are volumetrically very large, consisting of thick (50-150 ft;15-45 m), laterally extensive seams with significant amounts of late-stage biogenic methane. Wells drilled to exploit this resource in updip areas have benefited from dewatering associated with existing coal mining, as well as from existing pipeline infrastructure. In downdip areas, Fort Union coal beds are artesian aquifers and require significant drawdown for gas production. Innovative drilling and completion practices have been instrumental in lowering costs and increasing production, thus contributing to the overall success of the existing play. Production data suggest ultimate recoverable reserves of 0.3-0.4 bcf per well, making the play economical even at relatively low gas prices.