Abstract: Modeling Clastic Reservoir Properties, A Minimalist approach: An Example from the Appalachian Basin

Ronald R. McDowell, Michael E. Hohn, Ana G. Vargo, David L. Matchen

Several reservoir properties (porosity, permeability, water saturation, facies) were modeled for a West Virginia oilfield (Granny Creek) producing from the Lower Mississippian Big Injun sandstone. Modeling was conducted as part of a U. S. Department of Energy study of reservoir heterogeneity. The Granny Creek field is located in west-central West Virginia. Granny Creek is probably typical of oilfields in the Appalachian basin because of its small size (6 sq mi), early discovery (1924), long life (still producing), and paucity of geological and geophysical data.

Despite the fact that over 700 wells have been drilled in the field, only 30 were cored. Of these cores, 13 were determined to be lost. Fortunately, material from all cored wells had been subjected to whole core analysis which yielded laboratory measurements of porosity, permeability, and oil and water saturation.

The typical geophysical suite for the Granny Creek field consists of gamma-ray and density logs generally run as an adjunct to the casing process (although numerous older wells were open-hole completions). SP logs are practically nonexistent and only 20 induction logs were available for the field. Consequently, the "basic" geophysical data set for Granny Creek consisted of 275 gamma-ray and density logs.

Gamma-ray and density logs were correlated using automated correlation techniques. Statistical analysis of core and log (based on bulk density) porosity suggested that porosity was an acceptable proxy for permeability in Granny Creek. Water saturation was estimated for the entire field by kriging saturation values derived from deep induction resistivity measurements. Multivariate statistical analysis was applied to geophysical log values and petrographic (point count) data to characterize the facies present within the reservoir. Modeling efforts were successfully able to identify several types and scales of heterogeneity in the Big Injun reservoir in Granny Creek, and to tie these to the non-uniform distribution of production observed for the field.

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