Preliminary Feasibility Study of the Coal-Bed Methane Resource in Pennsylvania

MARKOWSKI, ANTONETTE K., Pennsylvania Geological Survey, Harrisburg, PA

Coal-bed methane gas content data were obtained from exploratory drill holes, premining degasification drill holes, and methane recovery test projects from the Main Bituminous and Northern Anthracite fields of Pennsylvania.

Exploratory coal cores tested ranged from the Pennsylvanian-Permian Dunkard Group to the Pennsylvanian Allegheny Group. Total gas contents were determined for each coal sample by using the U.S. Bureau of Mines direct method of testing. Graphical analyses of depth and thickness vs. total gas content revealed a direct correlation between depth and gas content. However, further study is needed to determine if significant gas contents are a functions of thickness.

Methane accounted for 90% and greater of the gas from each coal sample. Higher molecular weight hydrocarbons (alkanes) were also detected.

Gas values were approximately 1000 Btu/scf, comparable to that of natural gas. Extremely low heating values, however, accompanied shallow, above-drainage coal beds (less than 500 ft) proximal to mining operations.

Geologic factors that determine the feasibility of coal-bed methane development are (1) coal rank, (2) depth of overburden, (3) coal-bed thickness, (4) favorable structure and fracture permeability, (5) permeability of adjacent strata, (6) water content, and (7) pressure/stress relationships. The developer must also evaluate economic, political, and legal issues when planning a project in the Northern Appalachian coal basin.

Most of the available coal information in Pennsylvania is based on the minable coals. A more definitive estimate of the basin's deepest coal resources and gas contents are critical to the development of coal-bed methane as a resource.

AAPG Search and Discovery Article #91005 © 1991 Eastern Section Meeting, Pittsburgh, Pennsylvania, September 8-10, 1991 (2009)