This paper presents results from the study to improve the impure CO2 minimum miscibility pressure (MMP) prediction capability. The MMP data base was obtained from laboratory slim tube runs. Rigorous criteria for MMP determinations were established. These data were correlated as a function of mole fraction of contaminants in CO2, as a function of injection gas pseudocritical properties, and using a modified Peng-Robinson equation of state, with average errors in the range of 2 to 6 percent. The CO2 impurities were N2, C1, C2, C3, C5. Concentrations of impurities varied from 0 to 30 mole percent.

Comparisons with literature data indicate that the correlations, although developed using only West Texas oils, can be generalized to include a wide spectrum of reservoir fluids. These correlations, when compared to others in the literature, are found to be superior for injection gas mixtures which contain nitrogen and methane contaminants.

An ARCO developed compositional simulator was calibrated using slim tube and PVT data from the West Texas oil-CO2 system. The model simulates recovery curves reasonably well and predicts the pure and impure CO2 minimum miscibility pressures for West Texas oils to within 50-150 psi.

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