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Subsurface Study of the Lewis Shale in the Southern Washakie and Sand Wash Basins using Borehole Images, Core, Well Log, and Seismic Data

G. E. Minton
Colorado School of Mines, Department of Geology and Geological Engineering, Golden, CO

The purpose of this study is to interpret the depositional environment of the southern Washakie and Sand Wash Basins within a sequence stratigraphic framework, with an emphasis on the geological framework and reservoir architecture in the area of recent hydrocarbon discoveries. The study will examine the petroleum system in the basin with respect to the sequence stratigraphic analysis and develop predictive models for reservoir quality sand bodies. The study is based on borehole-image interpretations, core description, well log correlation, and seismic data of the Lewis Shale in the southernWashakie and Sand Wash Basins. These data are used to construct two regional northeast-southwest–oriented cross sections across the basins.

This work is done as a part of the Lewis Shale Consortium at the Colorado School of Mines and incorporates recent and current work from several other students in the Lewis Shale Consortium. Interpretation of core, borehole image logs, well log, and seismic data will build on interpretations of similar data by other students. The northeast cross section begins with wells that are at the southern end of most of the previous work and continues to the southwest. When completed this will create a two-dimensional sequence stratigraphic interpretation across the entire Washakie and Sand Wash Basins.

The petroleum system in the basins will be examined with respect to the sequence stratigraphic analysis. The Lewis Shale contains finegrained turbidite sandstones that act as natural gas reservoirs. The purpose of this aspect of the study is to determine the geologic framework of the sandstones within the study area with emphasis on the architectural elements in the area of recent hydrocarbon discoveries. Understanding gained by Consortium sponsored outcrop studies on the northeast end of the study area will be incorporated into the reservoir scale architectural elements.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid