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The AAPG/Datapages Combined Publications Database

Wyoming Geological Association


Wyoming Geological Association Guidebook - 2002 Field Conference “Wyoming Basins” and 2003 Field Conference Wyoming Oil: Resources & Technology “Reversing the Decline” (2003)
Pages 89-99

Preliminary Assessment of Previous HitReservoirNext Hit Quality Controls in Lewis Shale Sandstones, South-Central Wyoming

Geoffrey Thyne, Ira Pasternack, Donna S. Anderson


The Dad Previous HitSandstoneNext Hit member of the Upper Cretaceous Lewis Shale, Wyoming, is a lithic-rich fine-grained Previous HitsandstoneNext Hit and a difficult exploration target. A preliminary analysis of petrophysical, petrological and stratigraphic information was made to determine the major factors that control Previous HitreservoirNext Hit quality (Previous HitporosityNext Hit and permeability). The data included 718 conventional core plug analyses supplemented with 70 thin sections. The petrophysical data show a wide range of Previous HitporosityNext Hit and permeability for individual wells and fields that is not directly related to depth of burial. The sequence of diagenetic events was similar for all the samples studied. The important diagenetic factors include physical compaction, including compaction of ductile grains and framework grains that are altered to clay, calcite and quartz cementation, and late secondary Previous HitporosityNext Hit development. Calcite and quartz cement are locally important, but are usually secondary Previous HitporosityNext Hit loss mechanisms compared to compaction. Production data from Hay Previous HitReservoirNext Hit show an interesting trend where the majority of petroleum produced is derived from one Previous HitreservoirNext Hit interval. This implies a stratigraphic as well as diagenetic control on Previous HitreservoirTop quality.

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