Design of a Major CO2 Flood—North Ward Estes Field, Ward County, Texas
R. Winzinger, J. L. Brink, K. S. Patel, C. B. Davenport, Y. R. Patel, G. C. Thakur, 1991. "Design of a Major CO2 Flood—North Ward Estes Field, Ward County, Texas", The Integration of Geology, Geophysics, Petrophysics and Petroleum Engineering in Reservoir Delineation, Description and Management, Robert Sneider, Wulf Massell, Rob Mathis, Dennis Loren, Paul Wichmann
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The reservoir engineering aspects of the design of a major West Texas CO2 flood are presented.
A detailed fieldwide geologic study was conducted to characterize the principal Yates reservoirs which consist of very fine grained sandstones to siltstones separated by dense dolomite beds.
A CO2 injectivity test was conducted to obtain CO2 injection rates and to identify any reduction in injectivity either during or following CO2 injection. Laboratory work included oil-CO2 phase behavior, slim tube tests with pure and contaminated CO2, and corefloods to determine recovery of waterflood residual oil by CO2 flooding for various WAG ratios.
A comprehensive waterflood evaluation proceeded the selection of average pattern models for reservoir simulation. These three-dimensional models, which have up to eleven layers each, were history matched over the 35-year waterflood period. Predictions were made for continuation of the waterflood and for CO2 flooding. Scale-up procedures were developed to predict from the average patterns the incremental oil production for the entire project area. Additional reservoir simulation was conducted to study the differences in recovery efficiency between line drives and five spots, the optimum economic slug size and the changes in hydrocarbon gas composition and GOR due to the stripping effect of CO2.
A comparison of the predicted performance with the actual performance since start-up in early 1989 will also be presented.