10.5.12 Vapor-Liquid Equilibrium

A vapor-liquid equilibria (VLE) test is a specialized PVT test that is used to represent phase equilibria in a gas injection enhanced oil recovery (EOR) process. In this test, a mixture of oil and injection gas is equilibrated in a fixed condition of pressure and temperature where two distinct vapor and liquid phases are present. Composition and pressure (generally at fixed reservoir temperature) of the system is designed in such a way that equilibria is established where maximum mass transfer occurs between the two phases (near critical condition/fluid). Properties of each phase (composition, density, viscosity) are also used to optimize an equation-of-state model to represent phase equilibria during gas injection EOR process.