--> Abstract: Complex Facies Distribution of a Leveed-Channel System, Lewis Shale, Wyoming, by Staffan K. Van Dyke and Roger M. Slatt; #90039 (2005)

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Complex Facies Distribution of a Leveed-Channel System, Lewis Shale, Wyoming

Staffan K. Van Dyke1 and Roger M. Slatt2
1 Vanco Energy Company, Houston, TX
2 University of Oklahoma, Norman, OK

Nine channel-fill sandstones, separated by thin-bedded mudstones, comprise a 255ft thick outcrop stratigraphic succession of the deepwater Cretaceous Dad Sandstone Member, Lewis Shale, Wyoming. This succession was characterized by measuring 121 closely-spaced stratigraphic sections, decimeter-scale GPS-tracing (Global Positioning System) of outcrop and bed boundaries, and the drilling and gamma-logging of 8 shallow boreholes. A partial-3D facies and architectural model was built using GocadTM.

Four of eight (total) channel-fill facies are particularly diagnostic of channel subenvironments. Most channel-fill facies are complexly interbedded, but there is a tendency for shale-clast conglomerates and slumped beds to comprise the base and one side of a channel-fill, whereas cross-bedded to massive sandstones comprise the opposite side. This distribution of facies suggests they filled sinuous channels, with the shale-clast conglomerates representing a steep-gradient ‘cutbank' side and the cross-bedded to massive sandstones representing a shallower-gradient ‘point-bar' side.

This 3D outcrop characterization provides an excellent, scaled analog for fine-grained leveed channel reservoirs. The complex stratigraphy indicates individual channel sandstones can be mutually isolated reservoirs as well as having complex internal reservoir fluid flow.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005