Estimation of CO2 Minimum Miscibility Pressure for One of the Iranian Oil Reservoirs (Laboratory Study)

The miscibility condition is determined by conducting displacement tests at various pressures. Recovery is expected to increase by raising the displacement pressure, and however, it will stay almost constant above the MMP. In this study to estimate MMP of one of the Iranian oil reservoirs with pure CO2, a slim-tube test was performed under constant CO2 injection rate at different displacement pressure above the bubble point. Input and output pressures were continusly monitored during the test. The effluent liquid was flashed to atmospheric conditions; it is weighed and its density is measured for calculating the volumetric oil recovery. The produced gases are passed through gas chromatography for compositional analysis. The oil recovery was plotted against the injection pressure at 1.2 pore volume of injection fluid. The results show that the oil recoveries are more than 90% of original oil in place for all pressures with a constant slop above the bubble point pressure. Therefore, MMP should be the same as bubble point pressure. In addition, effluent gas composition, pressure drop across the slim-tube and no methane bank existence confirm the miscible condition.