Coalbed Methane Potential and Exploration Strategies for the Mid-Continent Region

A. R. Scott
Altuda Geological Consulting, San Antonio, TX ([email protected])

Coalbed methane resources of the mid-continent region are estimated to be at least 11 Tcf in the Arkoma, Cherokee, and Forest City Basins and renewed coalbed methane exploration efforts are underway. Middle and Late Pennsylvanian sediments in the mid-continent region were deposited in dip-elongate fluvial-deltaic facies in which peat accumulated on delta plains in swamps and marshes, and in interdeltaic embayments such as lagoons and bays. Although many coals are of mineable thickness, they are relatively thin compared to coal accumulations of the western U.S. Significant peat accumulation did not occur in for a variety of reasons, including deposition on a stable cratonic platform, which resulted in the removal of peats during fluvial erosion of underlying deltaic deposits. Additionally, relatively slow subsidence rates on the stable platform, associated with delta lobe abandonment, probably resulted in extensive reworking of the thin peats. However, the presence of high gas contents at relatively shallow depths and the presence of gassy coal mines are positive indicators for the coalbed methane potential of the region and economic recovery of coalbed methane is probable. The key hydrogeologic factors that will affect coalbed methane producibility include the depositional systems and coal distribution, tectonic/ structural setting, coal rank, gas content, permeability, and hydrodynamics. Exploration strategies based should include both regional and local assessments of the interplay of these six hydrogeologic factors through geologic time.

AAPG Search and Discovery Article #90903©2001 AAPG Mid-Continent Meeting, Amarillo, Texas