--> ABSTRACT: Devonian Shales of Central Appalachian Basin: Geological Controls on Gas Production, by P. H. Lowry, T. Hamilton-Smith, and R. M. Peterson; #91022 (1989)

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Devonian Shales of Central Appalachian Basin: Geological Controls on Gas Production

P. H. Lowry, T. Hamilton-Smith, R. M. Peterson

Gas reserves of the Devonian shales of the Appalachian basin constitute a large, underdeveloped resource producing from fractured reservoirs. As part of ongoing Gas Research Institute research, K&A Energy Consultants, Inc., is identifying geological controls on gas production. Preliminary findings indicate that local gas production is controlled by a combination of structure and stratigraphy. Regional geological review indicates that Devonian sedimentation and structure is influenced by repeated reactivation of basement faults. Site-specific geologic studies indicate that depositional and structural mechanisms vary substantially throughout the basin. Gas production on the eastern margin of the producing area is controlled by an Alleghenian thrust front located by Gren ille normal faults. High-capacity wells are associated with tear faults in the thrust sheets. To the southwest, deformation is controlled by both Grenville and Rome trough basement faults. Reactivation of these faults during later orogenic events produced a complex of high-angle reverse and strike-slip faults. Fracturing in the Devonian shales is produced by shearing and flexure associated with these structures. Syndepositional movement of the basement structures influenced the deposition of coarser grained turbidites and tempestites. The combination of fractures and coarser clastic beds provides effective reservoir systems. The shale contains abundant organic material consisting of terrestrial plant debris and marine algal remains. Thermal maturation of this material produced gas which harged the lower reservoir systems. Exploration along reactivated structural trends is an effective strategy for locating Devonian shale gas accumulations. This approach may also apply to other producing strata in the basin.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.