Coal-Bed Methane--An Unconventional but Viable Source of Natural Gas

HALLINGER, DONALD E., Southern California Gas Company, Los Angeles, CA

As of December 31, 1988, the Potential Gas Committee, a group of industry experts, estimated that the remaining undiscovered potential supplies of natural gas amounted to 795.6 trillion cubic feet (TCF) in the United States, including the offshore areas. Besides the conventional sources, the sandstone and carbonate reservoirs that geologists have been looking for since Drake, there are a number of unconventional sources of natural gas. One of these, coal-bed methane (CBM) is being actively developed today and promises to provide significant additions to the proved reserves of this nation in the next ten years. The potential supplies of CBM are variously estimated to be between 400 to 1000 tcf, or equal to the remaining undiscovered conventional supplies of natural gas. If these estima es are real, they will have a profound effect on forecasts of future prices and availability of natural gas. How valid are these estimates? At what rate will this new source of natural gas come on stream? The answers to these questions are dependent in part upon the uniqueness of the coal reservoir. Coal can contain more natural gas than a comparable sized conventional reservoir. A coal reservoir exhibits positive production decline instead of the negative decline of conventional reservoirs. There are legal and economic considerations that will affect the development of this relatively new and exciting source of natural gas. All of these questions will be discussed by the author.

AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)