Abstract

The Greater Green River, Piceance, Powder River, and Raton Basins contain approximately 161 Tcf (4.55 Tm³), or 41 percent, of the United States coalbed methane resources of 392 Tcf(11.09 Tm³). Their potential to produce coalbed methane is compared and evaluated in the context of geologic and hydrologic attributes identified in the San Juan Basin, the nation's leading coalbed methane producer. The major comparative criteria used to evaluate the coalbed methane potential of these basins are (1) coalbed methane resources, (2) geologic and hydrologic factors that predict areas of high coalbed gas producibility, (3) coalbed thermal maturity, and (4) economic constraints (including data base availability, production history, and industry activity and infrastructure). The Greater Green River and Piceance Basins have a greater potential to make a significant near-term contribution to the nation's gas supply. These basins have large gas resources (29 and 84 Tcf [0.82 and 2.38 Tm³], respectively), coals of high rank (R_o >0.73 percent) and high gas content (150 to 450 ft³/ton [4.7 to 14.0 m³/t]), and established coalbed methane production. The Greater Green River and Piceance Basins have thick coal-bearing units offering numerous coalbed methane targets. Low coal-seam permeability, however, limits the coalbed methane potential of the Piceance Basin. The Powder River and Raton Basins have gas resources estimated to range between 16 and 30 Tcf [0.45 and 0.85 Tm³) and 12 and 18 Tcf [0.34 and 0.51 Tm³], respectively, and are judged to have the lesser coalbed methane potential. The Powder River Basin also has thermally immature coals of low rank (vitrinite reflectance [R_o] <0.50 percent) and low gas content (<100 ft³ /ton [<3.1 m³/t]). The Raton Basin has thin, discontinuous coal beds, small coal resources (17 billion tons [15.4 billion metric tons]), and a limited data base (<250 geophysical logs) and lacks gas transmission pipelines. Limited production and industry activity further constrain the Powder River and Raton Basins' near-term potential for contribution to the nation's gas supply.