Abstract: Coalbed Methane Resources in the Northern Appalachian Coal Basin, Southwestern Pennsylvania and North-Central West Virginia

MARKOWSKI, ANTONETTE K., WILLIAM C. GRADY and DAVID L. MATCHEN

A mapping investigation of the regional geology of coal-bearing intervals and its influence on coalbed methane (CBM) potential focused on and showed that the Allegheny Formation of northern West Virginia (Allegheny Group of southwestern Pennsylvania) and basal part of the Monongahela Group (Pittsburgh coal) of these two areas contain the most prospective methane-producing coals. An "operational" Allegheny Formation/Group was defined for coal beds in the subsurface. Total inplace coalbed gas resource estimates to date are 61 Tcf for the Northern Appalachian Coal Basin.

Pennsylvania's Campbells Mill pool, Indiana County, is the largest commercial CBM project with 26 producing wells. Higher gas contents, increasing rank, and possibly tighter folding indicate more favorable conditions for production at the northeastern end of the study area in Indiana County. The "potential" for CBM is affected by coal-quality parameters, particularly ash yield, rank, and petrographic composition. In West Virginia and Pennsylvania, vitrinite-rich bituminous coals range in reflectance from 0.5 to 1.9%, the rank range over which most thermally derived CBM is known. Only coals constrained by geographic (primarily tectonic) and stratigraphic (primarily depth of burial) rank factors could potentially contain commercial quantities of methane.

In West Virginia, development of Pittsburgh and Allegheny coals has been attempted with mixed results. Seven Pittsburgh mine gob wells have reportedly produced 0.47 Bcf since 1922. According to a recent well survey, low initial flow tests reported in old (1800 to 1929) Allegheny wells may be caused by the presence of numerous oil and conventional gas wells that were drilled to deeper targets, left open and abandoned, resulting in the release of much of the available CBM.

AAPG Search and Discovery Article #90939©1997 AAPG Eastern Section and TSOP, Lexington, Kentucky