Outcrop Analysis of a Sand-Rich, Basin-Floor Turbidite System, Permian Bell Canyon Formation, West Texas
Published:November 01, 1999
Mark D. Barton, Shirley P. Dutton, 1999. "Outcrop Analysis of a Sand-Rich, Basin-Floor Turbidite System, Permian Bell Canyon Formation, West Texas", Advanced Reservoir Characterization for the 21st Century, Tucker F. Hentz
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Outcrops of the Bell Canyon Formation, Delaware Mountain Group, in Culberson County, Texas, were studied to better understand the sandstone depositional processes and determine the dimensions and arrangement of sandstone bodies. The depositional model developed from outcrop can be used to guide reservoir characterization of Delaware sandstone fields. The Bell Canyon Formation is a deep-water siliciclastic unit that accumulated in the Delaware Basin, located in West Texas and southeast New Mexico, during the Late Permian. The Bell Canyon is a sand-rich system that displays a net-to gross of about 70 percent. Grain size is limited to fine sand and coarse silt, and clay-size material is almost entirely lacking.
Stratigraphic relationships indicate that the outcrop sandstones were deposited in a toe-of-slope or basin-floor setting by a system of leveed channels having attached lobes and overbank splays that filled topographically low interchannel areas. Channels are largely filled with massive and cross-stratified sandstones. They are as much as 15 m thick and 100 to 300 m wide. The channels are arranged in a radial pattern that bifurcates and expands down dip. The channels are flanked on both sides by wedges composed of thinly bedded sandstones and siltstones that are interpreted as levees. The levees thin away from the channel, decreasing in thickness from 8 to 1 m over the distance of 1 km. The levees are onlapped by massive sandstones interpreted as interchannel lobes or splays. The lobes, as much as 8 m thick and 10 km wide, display a broad tabular to irregular geometry.
Individual channel-levee and lobe complexes appear to stack in a compensatory fashion and are separated by laterally continuous, meter-thick laminated siltstones. The laminated siltstones are interpreted to have been deposited by the settling of marine organic matter and airborne silt during periods when coarser particles were prevented from entering the basin. The paleogeographic setting, absence of mass-movement features, and high preservation of facies indicate that the outcrop sandstones were deposited in a basin-floor setting.