--> Integrated Reservoir Characterization: A Collaborative Study in a West Texas Carbonate/Clastic Reservoir, by R. L. Chambers, H. Tan, J. Eager, M. Ross, J. Mansoori, A. Vassiliou, P. Barron, W. Rizer, J. Queen, D. Cox, D. Ragland, J. Sinton, J. Ballard, G. Kokkoras, P. Buller, L. Lines, P. Guerendel, A. Track, J. Harris, S. Lazaratos, and M. Van Schaak; #90986 (1994).

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Abstract: Integrated Reservoir Characterization: A Collaborative Study in a West Texas Carbonate/Clastic Reservoir

Richard L. Chambers, Henry Tan, John Eager, Mike Ross, John Mansoori, Anthony Vassiliou, Patty Barron, William Rizer, John Queen, Dale Cox, Debbie Ragland, John Sinton, Jim Ballard, George Kokkoras, Paul Buller, Larry Lines, Philippe Guerendel, Antoine Track, Jerry Harris, Spyros Lazaratos, Mark Van Schaak

In 1992, a collaborative effort in enhanced reservoir characterization was undertaken by Amoco, Conoco, Stanford University and Schlumberger in the Amoco North Cowden Unit 12-acre CO2 Pilot area, west Texas. The objective is to characterize heterogeneity and flow anisotropy in the Grayburg reservoir through an integrated geophysical/geological approach involving 3-D seismic, multicomponent VSP, traveltime tomography, crosswell reflector imaging, channel wave analysis, petrophysical measurements on core, and interpretation of modern logs suites. Grayburg reservoirs are characterized by lateral and vertical heterogeneity and in the study area consists of 450 feet of interbedded dolomites and siltstones. In the pilot area, most production is from the second siltstone interval. Geostatistical analysis of log, petrophysical and 3-D seismic data show that pay zones are aligned roughly north-south, parallel to the paleoshoreline.

Tomographic and reflector image processing, channel wave analysis and log data indicate a high degree of connectivity of the primary reservoir zone within the pilot area. Analysis of multicomponent VSP data shows only a small amount of shear wave splitting with polarizations aligned ENE, which parallels the maximum horizontal in situ stress interpreted from acoustic borehole imaging data and also aligns with the direction of preferential flow determined from waterflood breakthrough data.

When quantitatively integrated, these data provide a highly constrained description of this complex carbonate/clastic reservoir. Stochastic reservoir descriptions, generated by geostatistical conditional simulation techniques are used to address uncertainty in future production performance. A conventional deterministic "layer-cake" description of this reservoir shows more optimistic ultimate recovery than flow prediction curves from multiple stochastic reservoir descriptions.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994