Correlations of minimum miscibility pressure for pure and impure CO2 in low permeability oil reservoir

Abstract

Minimum miscible pressure (MMP) is an important indicator to evaluate the miscibility of CO2 with oil, and it is of paramount importance to the implementation of CO2 flooding. In this study, the sensitivities of MMP to its influencing factors were analyzed quantitatively. And the MMP correlations applying for pure and impure CO2–oil in low permeability reservoir were presented. These correlations are conducive to predicting MMP quickly and precisely when limited experimental data are available. In low permeability reservoirs, the main sensitive factors of MMP are reservoir temperature, oil components (C5+ molecular weight, volatiles and intermediates) and the components of injected gas (characterized with pseudo-critical temperature). MMP increases with the volatile/intermediate ratio, especially in the neighborhood of unity and decreases with the pseudo-critical temperature of impure CO2. MMP shows strong sensibility to the pseudo-critical temperature of impure CO2 when the critical temperature is less than that of pure CO2.