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

CO2 flooding is considered to be one of the most effective methods in enhanced oil recovery of the light oil reservoir. Depending on the operating pressure, the gas injection process could be miscible or immiscible. The Minimum Miscibility Pressure (MMP) is the most important parameter for assessing the applicability of miscible gas flood for an oil reservoir. 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 MMP between one of the Iranian reservoir oil and CO2 is measured. Input and output pressures are monitored during the test. The effluent liquid was flashed to atmospheric conditions; its volume is measured for calculating oil recovery. The produced gases are passed through gas chromatography for compositional analysis. 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.