Enhanced Method-of-Characteristics Approach for Determination of Minimum Miscibility Pressure in Displacements with Bifurcated Phase Behavior

Abstract

Determination of minimum miscibility pressure (MMP) is an imperative component of optimally designing miscible gas injection processes. Semianalytical method of characteristics (MOC) is superior to other available computational and experimental methods for MMP determinations. However, the MOC method inaccurately overestimates MMP for complicated CO2 displacements involved with bifurcated phase behavior. This drawback has been addressed in a study wherein a time-consuming and cumbersome modification has been suggested. In this study, a prompt and convenient approach is introduced to precisely consider the impact of bifurcated phase behavior on MMP calculations. This approach is established based upon an innovative hypothesis that bifurcated phase behavior merely emerges where a key component with the largest percentage in the mixture disappears through the composition route from initial oil to the injection gas. The performance of the proposed approach is minutely examined within several displacement scenarios with an emphasis on pure CO2 injection. The obtained results confirm that the bifurcated phase behavior can be accurately distinguished within the composition route. Furthermore, the procedure of MMP calculations is achieved mush swifter especially for multicomponent mixtures (i.e., up to 170% less in time). On the basis of the above arguments, it is clear-cut that the proposed method holds a remarkable potential in the applications related to miscible displacement.