Injection of gases into a reservoir for enhanced oil recovery results in complex fluid phase behavior that cannot be modeled by black oil simulators. This interaction of flow and phase behavior is best captured by fully compositional simulators. A drawback of fully compositional simulators is that they require accurate reservoir fluid characterizations by equations of state (EOS) to capture the phase interactions in miscible gas floods. Another disadvantage is that EOS are computationally intensive. An EOS is typically tuned to standard PVT data, which may include multicontact experiments and swelling tests. The standard method of tuning, however, does not incorporate important displacement parameters such as the minimum miscibility pressure or enrichment (MMP or MME) or the likely compositions that result in a reservoir from condensing-vaporizing displacements. / text