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Abstract: Outcrop to Subsurface Characterization and Correlation of Turbidite Deposits, Lewis Shale, Wyoming

WITTON, BETH M., Colorado School of Mines, Dept. of Geology and Geological Engineering, Golden, CO

The Upper Cretaceous Lewis Shale, Greater Green River Basin, Wyoming, provides a unique opportunity to study lateral and vertical attributes of turbidite deposits in outcrop. While the gross geometry of turbidite deposits can be seen using 3-D seismic data, smaller scale continuity and connectivity issues are commonly beneath seismic resolution. Integration of outcrop descriptions with logs, core, and seismic data provides an excellent method to develop criteria for recognizing lateral continuity of prospective reservoirs with similar facies.

Methods to be employed include: 1) Measure multiple stratigraphic sections of Lewis Shale turbidites in outcrop, and log stratigraphic sections with outcrop gamma-ray logs. The study will emphasize characterization of lenticular, compartmentalized sands and more laterally continuous thin-bedded sands and silts. The spacing of the sections will be positioned to simulate typical well spacing. 2) Utilize outcrop observations to interpret and correlate wireline logs suites obtained from the correlative Barrel Springs oil field located six miles west of the outcrop. Log suites include STAR (borehole images), XMAC (dipole sonic) and MRIL (nuclear magnetic resonance images). 3) Synthesize surface and subsurface data into an overall geometric and petrophysical characterization of these turbidite deposits. The study will include 3-D models of lateral facies continuity used for model development of such strata elsewhere in the Lewis Shale and in the deep water/subsalt Gulf of Mexico. Large hydrocarbon resources are trapped in similar sands in both of these provinces.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid