Compositional modeling with an equation of state

A description is given of an implicit-pressure explicit-composition and explicit-saturation compositional model. The model uses an equation of state (Peng-Robinson) for phase equilibrium and density calculations. Interfacial tension effects are considered also. The formulation of the pressure equation yields a symmetric and diagonally dominant matrix that allows the use of the iterative conjugate gradient method for large systems. Simulation of laboratory CO/sub 2/ displacements shows good agreement between calculated and experimental results. The influence of interfacial tension is investigated. Physically reasonable results also have been obtained for hypothetical areal and cross-sectional problems. 19 refs.