James R. Staub¹
(1) Southern Illinois University, Carbondale, IL

Abstract: A repeating coal-bed sequence in the central Appalachian Basin

Thirteen southern West Virginia coal beds were investigated to determine coal-bed methane source rock/reservoir character. Beds were divided into their component sedimentary parts or benches by identifying bounding surfaces within beds. Paleo-peat mire morphology at the bench level was determined using both three-dimensional shape analysis and petrographic indices. Planar and raised paleo-peat mire benches were identified. Macroscopic coal composition was compared to mire type. Gas and splint coals have the highest fracture/cleat density. All gas coal and some splint coal benches were derived from raised mires. Within splint coals of the same rank fracture/cleat spacing was much closer in raised mire benches. A repeating sequence was identified within beds. This sequence generally consists of 1) planar mire formation with evolution to raised mire status, 2) bounding surface formation, and 3) planar mire formation with subsequent bed termination. A succession through time related to the raised mire formation also was identified. It indicates optimum conditions for raised mire and source rock/reservoir development occurred during late Westphalian A to early Westphalian B time. In addition, raised mire area long axis orientation trends are present. Prior to extensive mining in this basin there was an optimum stratigraphic range and orientation trend to target for coal-bed methane exploration and development. The observed coal-bed sequence and succession suggests that in other basins, particularly marine-influenced foreland basins, similar target situations exist.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana