This paper describes technical enhancements to an existing compositional reservoir simulator, and the improved simulation results achieved in a full field simulation study of the Smørbukk Sør Field. The paper also describes a multi-discipline approach in the execution of a simulation study, and the cooperation between Mobil's U.S. technical center and a European affiliate.

The technical enhancements made to Mobil's compositional simulator PEGASUS were (a) improved interfacial tension corrections to relative permeability in miscible flooding, (b) a variable bubble-point and composition with depth function based upon chemical equilibrium, and (c) application of the Babu-Odeh analytical horizontal well model. These features were not available in compositional reservoir simulators at the time the study was conducted.

The interfacial tension correction for miscible flooding provided production performance predictions that could be used with confidence in the evaluation and selection of the optimum production mechanism for the Smorbukk Sør field. The variable composition with depth correlation demonstrated that a gas cap is not likely to exist considering the measured bubble point gradient. The horizontal well model function confirmed that improved productivity could be achieved with fewer development wells, thus contributing to the selection of the most cost effective development scheme.

The primary purpose of the study was to compare the impact of gas and water injection on ultimate recovery and production performance. Secondary objectives were to determine maximum productivity with the fewest number of production wells, and to maximize recovery at peak production. While simulation results marginally favored water injection, gas injection was considered the preferred production mechanism because of gas disposal considerations.

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