ABSTRACT: Coalbed Methane Potential of the Greater Green River, Piceance, Powder River, and Raton Basins

AMBROSE, W. A., ROGER TYLER, A. R. SCOTT, and W. R. KAISER, Bureau of Economic Geology, University of Texas at Austin, Austin, TX

The Greater Green River, Piceance, Powder River, and Raton basins contain approximately 38% of the United States coalbed methane resource of 392 tcf. Their potential to produce coalbed methane was evaluated in a comparison of their geologic and hydrologic characteristics with the San Juan basin, which is the leading United States producer of coalbed methane. Major controls on the occurrence and production of coalbed methane in the San Juan basin are structural and depositional settings, hydrologic regime, and thermal maturity. Collectively, these factors determine coal and gas resources, maximum- and net-coal thicknesses, thickness of coal-bearing interval, permeability, coal rank, and gas content. From available data, we reviewed geologic and hydrologic controls on coalbed methane, a well as economic criteria, such as pipeline availability, in each of these basins.

In a two-step evaluation process, the Powder River and Raton basins were assigned secondary coalbed methane potential. Thermally immature coal beds with low gas content in the Powder River basin produce great volumes of water that create disposal problems. Although the Raton basin has shallow high-rank coals, it contains thin coal beds, lacks pipelines, and has a poor database.

The Greater Green River and Piceance basins emerged with the highest potential and were then compared to each other. The Greater Green River basin is geologically and hydrologically superior to the Piceance basin and offers major potential to make a significant contribution to the United States gas supply. The Greater Green River basin is large, contains several coal-bearing intervals that collectively are thousands of feet thick, and has higher overall coalbed permeability as inferred from hydrologic data. Although coal beds in the Piceance basin have high coal rank and gas content, these coal beds have low permeability, which can limit reservoir producibility.

AAPG Search and Discovery Article #91017©1992 AAPG Rocky Mountain Section Meeting, Casper, Wyoming, September 13-16, 1992 (2009)