--> Abstract: Geologic Model for Identification of Higher Devonian Shale Gas-Production Potential, by P. H. Lowry, R. W. Brown, J. W. Hobson, and A. Olszewski; #91005 (1991).

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Geologic Model for Identification of Higher Devonian Shale Gas-Production Potential

LOWRY, PATRICK H., and ROBERT W. BROWN, K & A Energy Consultants, Inc., Tulsa, OK, JOHN W. HOBSON, Consultant, Cambridge Springs, PA, and ADAM OLSZEWSKI, ResTech-Pittsburgh, Pittsburgh, PA

Areas of higher gas production within the Devonian shales of the Appalachian basin may be identified with the aid of an integrated geologic model. Lithology and fractures combine to form complex reservoir systems. The search for these reservoirs is aided by integration of log lithofacies analysis and interpretations of seismic data.

Gas Research Institute-sponsored research has shown that in areas where siltstones and silty shales occur, they contribute most of the gas production. In black shale-dominated areas, thin silt lamination, in certain sequences, appears to provide permeability for gas flow. These lithological sequences relate to lithofacies, which can be mapped, providing the means of predicting occurrence and thickness.

Natural fractures provide higher permeability pathways for gas flow and often are associated with Devonian structural trends. These trends are frequently the result of reactivation of preexisting basement structures. Although some fractures may have been formed during early tectonic events, many may be due to relatively recent reactivation along older zones of weakness.

Reactivated faults often propagate upward through the Paleozoic section and are identifiable using single-fold seismic data. The structural expression of the fault zones is often broad, low-relief clinoforms. These are internally complex as identified on seismic sections.

A geologist may look for areas of higher probable gas production by locating areas that exhibit elements of the geological model. Through the integration of core, logs, seismic, and well-test and production data, a localized reservoir model may be constructed aiding in the siting and completion of wells.

 

AAPG Search and Discovery Article #91005 © 1991 Eastern Section Meeting, Pittsburgh, Pennsylvania, September 8-10, 1991 (2009)