--> Abstract: Natural Fracture Characterization: A Key to Success in an Exploration Play, Converse County, Wyoming, by S. L. Parks, M. S. Gale, P. J. Bradley, and V. S. Mount; #90952 (1996).

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Abstract: Natural Fracture Characterization: A Key to Success in an Exploration Play, Converse County, Wyoming

Steven L. Parks, Melinda S. Gale, Paul J. Bradley, Van S. Mount

Numerous vertical wells drilled in the southern Powder River basin have encountered fractured, tight, overpressured, Cretaceous hydrocarbon reservoirs. These reservoirs demonstrate enhanced productivity and ultimate recovery with little to no water production. Effective exploration and development of these reservoirs includes a systematic approach to characterization and prediction of the fracture system.

Surface mapping within Cretaceous units along the southern and western margins of the basin revealed multiple fracture sets related to both regional and local tectonic events. A pre-Laramide regional fracture set oriented at approximately N70°E is dominant over the mapped 500 square mile area. This set displays a consistent frequency, direction, height, and morphology both in the surface and subsurface. Fractures in early Tertiary rocks within the basin are unidirectionally oriented along a WNW azimuth, a direction also found in the Cretaceous units.

Vastar Resources, Inc. is actively exploring fractured reservoirs in the Powder River basin with horizontal wells targeting the Niobrara and Frontier formations. Integration of the detailed surface outcrop studies with regional cross-sections, Landsat lineament analysis, FMS log data, 2D multicomponent/multisource shear wave seismic, and borehole breakouts (to determine present day stress) have been used to successfully predict the orientation, frequency, and degree of openness of the subsurface fracture system.

The consistency of the fracture system and its positive impact on reservoir productivity significantly enhance the prospectiveness of Cretaceous plays throughout the southern Powder River basin.

AAPG Search and Discovery Article #90952©1996 AAPG Rocky Mountain Section Meeting, Billings, Montana