Reservoir Modeling and Simulation for CO2 Flooding: the Effect of Reservoir Heterogeneity on Simulation Forecasts

Shaochang Wo, Enhanced Oil Recovery Institute, Dept. 4068, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82070, phone: (307)766-2780, fax: (307)766-2737, [email protected]

CO2 flooding has proven to be a viable enhanced oil recovery process in many geographic locations. The Tensleep Sandstone in the Bighorn and Wind River basins, Wyoming, contains the largest oil reserves in the state. Because of reservoir heterogeneity, as little as 10-15% of discovered oil in the Tensleep Formation is recoverable by current primary and secondary techniques. Many of the Tensleep reservoirs are potential candidates for CO2 flooding. To evaluate the effect of reservoir and fluid properties on CO2 flooding performance, a sensitivity study of reservoir modeling was performed on a five-spot injection-production pattern. A variety of reservoir configurations were simulated based on the large range of API gravities of the oils produced from the Tensleep Formation as well as its spatial variation and anisotropy of relative permeability published from previous studies. CO2 flooding is generally not sensitive to lithology but is sensitive to reservoir characteristics. For the Tensleep reservoirs, the actual performance of CO2 flooding will largely be controlled by the local compartmentalization. The ECLIPSE compositional simulator was used for this study.