Quantitative methods for reservoir characterization and improved recovery: Application to heavy oil sands

Improved prediction of interwell reservoir heterogeneity is needed to increase productivity and to reduce recovery cost for California's heavy oil sands, which contain approximately 2.3 billion barrels of remaining reserves in the Temblor Formation and in other formations of the San Joaquin Valley. This investigation involves application of advanced analytical property-distribution methods conditioned to continuous outcrop control for improved reservoir characterization and simulation. The proposed investigation is being performed in collaboration with Chevron Production Company U.S.A. as an industrial partner, and incorporates data from the Temblor Formation in Chevron's West Coalinga Field. Efforts during the past twelve months have focused on developing three-dimensional geologic models for reservoir characterization, incorporating permeabilities into the models, and then using the models for reservoir simulation. In conjunction with this work, five facies tracts have been identified in the Temblor Formation using cores and outcrops: incised valley, estuarine, tide- to wave-dominated shoreline, diatomite, and subtidal. Three-dimensional facies tract and facies group models have been constructed for two areas within West Coalinga Field. Additional work during the past year includes further investigation of the applications of the new drill-hole minipermeameter probe. The theory for analyzing radial gas flow from a cylindrical borehole into the surrounding medium has been expanded to include possible variations in system geometry. In addition, the physical basis for a spatial weighting function has been developed using streamline coordinates. The results are very encouraging for adapting the new probe design to various field situations. Permeability data collected from outcrop near Escalante, Utah, support a new concept for representing natural heterogeneity, which is called the facies-fractal concept [Lu et al., 2001]. We anticipate that applying the facies-fractal concept to the sedimentary structure at West Coalinga Field will be the main basis for simulating the oil recovery process. The simulation will be fully developed during the final project period. T2VOC, which is a numerical flow simulator capable of modeling multiphase, multi-component, nonisothermal flow, is being used to model steam injection and oil production for a portion of section 36D in West Coalinga Field. This simulator has been used extensively by government agencies and private corporations to model the flow of water, air (steam), and oil in multi-dimensional, heterogeneous porous media.