Calculation of minimum miscibility pressure

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A method is described and tested for calculation of minimum miscibility pressure (MMP) that makes use of an analytical theory for one-dimensional, dispersion-free flow of multicomponent mixtures. The theory shows that in a displacement of an oil by a gas with n c components, the behavior of the displacement is controlled by a sequence of n c−1 key tie lines. Besides, the tie lines that extend through the initial oil and injection gas compositions, there are n c−3 tie lines, known as crossover tie lines, that can be found from a set of conditions that require the extensions of the appropriate tie lines to intersect each other. The MMP is calculated as the pressure at which one of the key tie lines becomes a tie line of zero length that is tangent to the critical locus. The numerical approach for solving the tie line intersection equations is described; slim tube test and compositional simulation data reported in the literature are used to show that the proposed approach can be used to calculate MMP accurately for displacements with an arbitrary number of components present.