ABSTRACT: Coal-Bed Methane--New Energy for Today and the Future

D. Keith Murray, Stephen D. Schwochow

Coal is one of the richest known sources of hydrocarbons. This heterogeneous material has the unique characteristic of being both a source and a reservoir of natural gas. By virtue of their maturation to high rank, some coals have the capacity to generate more than 8,000 ft³ of methane per ton of coal. Although most of this gas eventually has been lost, over 400 trillion ft³ remains in place in United States coal basins. The Potential Gas Committee has estimated that at least 90 trillion ft³ likely are recoverable.

Coal-bed methane exploration requires application of both coal geology and petroleum geology as well as nonconventional approaches to reservoir engineering. With advanced technologies developed largely through cooperative efforts of the Gas Research Institute and industry, researchers and explorationists are better understanding the geological and engineering peculiarities of coal reservoirs.

Commercial coal-bed methane development occurs basically in two diverse geologic settings: (1) thin, shallow coals of Pennsylvanian age in the Black Warrior and Appalachian basins and (2) thicker, deeper coals of Cretaceous age in the Rocky Mountains, principally the San Juan, Piceance, Raton, and Green River basins. Recent exploration has targeted shallow, anomalously thick but lower-rank, low-gas-content Tertiary coals in Wyoming. Coal basins in Washington, British Columbia, and Alberta also show potential.

Methane in coal beds is an immense, virtually untapped source of environmentally acceptable, pipeline-quality energy. In light of increasing demand for natural gas, coal-bed methane is becoming an economically viable, low-risk exploratory and development objective.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990