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

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.