--> Coal-Sourced Compactional Traps in Sandstone Reservoirs: Similarities Between Northern West Virginia and WY, by A. V. Oldham, T. E. Repine, Jr., and D. W. Oldham; #90986 (1994).

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Abstract: Coal-Sourced Compactional Traps in Sandstone Reservoirs: Similarities Between Northern West Virginia and WY

Anne V. Oldham, Thomas E. Repine, Jr., David W. Oldham

Production of coal-sourced gas from sandstones of the Fort Union Formation (Paleocene) in the Powder River basin of Wyoming has been shown to be dependent on areas where differential compaction resulted in early-formed traps in which biogenic methane accumulated. This Rocky Mountain play may represent an analog to a northern West Virginia play in a thermally immature stage.

Subsurface studies of the Allegheny Formation and Pottsville Group (Pennsylvanian) in northern West Virginia indicate two different sandstone/coal relationships: (1) vertical stacking of thick channel-fill sandstones where syndepositional tectonic influence predominated, wherein coals interbedded with shales may be favorable targets for in-seam coal bed methane completions; and (2) offset-stacked fluvial channel-fill sandstones where differential compaction was the major syndepositional influence. These sandstones are often in contact with or partially replace an underlying coal (source) and are commonly overlain by floodplain shales (seal). As found in Wyoming, early formation of differential compaction traps may have allowed emplacement of biogenic gas which acted to retard a reduct on in porosity due to sandstone diagenesis until thermally-generated, coal-sourced methane became available for migration to these West Virginia sandstones.

In addition to expiration of the Section 29 tax credit, development of coal-bed methane in the northern West Virginia coal field has been hindered by gas ownership issues, moderate in-place coal-bed gas contents, and completion/production problems associated with development of an unconventional reservoir. As found in Wyoming, separate, or supplemental completion of coal-sourced sandstone reservoirs may enhance the economic viability of coal-bed methane development in West Virginia.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994