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Characterization
of Tensleep Sandstone
Reservoirs*
Search and Discovery Article #50024 (2005)
Posted November 27, 2005
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1Institute for Energy research, Department of Geology and Geophysics, University of Wyoming, Laramie, WY 82071, phone: 307-766-2791, fax: (307) 766-2737, ([email protected])
Abstract
Three important components must be
considered in the characterization of the Tensleep Sandstone reservoirs: (1)
depositional boundaries, (2) petrophysical facies, and (3) permeability
directionality. Depositional boundaries, resulting from grain size variation and
diagenetic modification, potentially act as flow barriers and buffers in
reservoir simulation. Regularly-oriented, high-ordered, depositional boundaries
can also cause permeability directionality. Petrophysical facies are
characterized by depositional texture, diagenetic fingerprints, porosity, and
permeability. Six petrophysical facies are suggested in the Tensleep reservoir
sandstones, including (1) uncemented, dolomite-sand-free, dune sandstone facies,
(2) cemented, dolomite-sand-free, dune sandstone facies, (3) cemented,
dolomite-sand-rich, dune sandstone facies, (4) uncemented, dolomite-sand-rich,
interdune sandstone facies, (5) cemented, dolomite-sand-rich, interdune
sandstone facies, and (6) cemented, dolomite-sand-rich sand sheet facies.
Permeability directionality is very clear on the core-plug scale. In checked
Tensleep sandstone cores, the maximum permeabilities range from 1.2 to 2.2 times
the 90-degree permeabilities, and from 2.2 to 14.2 times the vertical
permeabilities; and the 90-degree permeabilities range from 2.3 to 10.6 times
the vertical permeabilities. Precise characterization
of the depositional
boundaries, petrophysical facies, and permeability directionality is critical
for the geological modeling of Tensleep sandstone reservoirs.
Distribution, on outcrop, of petrophysical facies
