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Upper Cretaceous Lewis Shale, Great Divide Basin, WY: Seal Characterization and Occurrence within a Sequence Stratigraphic Framework

B. Castelblanco
Colorado State University, Department of Earth Resources, Fort Collins, CO

Deepwater clastic depositional systems like the Lewis Shale commonly form the top and lateral seals of large hydrocarbon reservoirs. Past research has focused mainly on understanding the depositional environment, architecture and sedimentological characteristics of reservoir sandstones. Although seal rocks play an important role in holding hydrocarbons within reservoir rocks, they have been less studied than the latter.

The main goal of this research is to better determine the characteristics of potential seals in the Lewis Shale within a sequence stratigraphic framework by integrating outcrop data (measured stratigraphic sections), core data and laboratory analyses including thin-section petrography, mercury injection capillary pressure (MICP), scanning electron microscopy (SEM), X-ray diffraction (XRD), x-ray fluorescence (XRF), total organic carbon (TOC) and Rock-EvalTM pyrolysis. Another equally important goal is to develop a statistical analysis of seal and flow barrier distribution at the field scale, which will ultimately allow seal quality prediction in areas of minimal or incomplete data. For purposes of this research the Lewis Shale will be studied in the Rawlins-Sierra Madre uplift and the Great Divide and Washakie basins, in the area between Rawlins and Baggs, Carbon County, south-central Wyoming. This research will ultimately allow seal quality prediction in areas of minimal or incomplete data.

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