Relation of Sedimentologic Features and Reservoir Quality in a Shelf Ridge Sandstone Deposit--Comparison of Outcrop and Subsurface Properties

S. R. Jackson, M. Szpakiewicz, L. Tomutsa

The High Energy Ridge Margin (HERM) facies of the Shannon Sandstone in the Salt Creek anticline area of the Powder River basin, Wyoming, is comprised of fine to medium-grained glauconitic sandstone (82%), which is cross-bedded, rippled, and burrowed, and shale and limonitic clay (18%). Histograms of log permeability-to-air values measured from 214 1-in. diameter cores drilled from the face of an outcrop of the HERM facies of the lower Shannon indicate the existence of two major permeability populations. These two permeability populations can be related to cross-bedded sandstone (higher permeabilities), and noncross-bedded, rippled, and burrowed sandstone with clay laminae (lower permeabilities).

Examination of the HERM facies in upper Shannon cores from Teapot Dome oil field, located 5 mi from the studied outcrop at a depth of 300 ft, indicate similar sedimentologic features and similar permeability populations related to cross-bedded and noncross-bedded subfacies within the HERM facies.

Comparisons of permeability and porosity histograms, cumulative distribution functions, correlation lengths, and natural logarithm of permeability versus porosity plots also indicate a strong similarity in HERM reservoir properties between outcrop and Teapot Dome field.

The similarities of outcrop and Teapot Dome permeabilities and porosities, which are from the same geologic facies but from different depositional episodes (upper and lower Shannon), suggest that rocks deposited under similar depositional processes within a given deposystem have similar reservoir properties.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.