An internally consistent approach for determining the properties of lumped components using a cubic equation of state

Abstract

Cubic equations of state, due to their simplicity and accuracy, are commonly used in reservoir simulation to predict phase behavior of petroleum reservour fluids. A cubic equation of state utilizes critical temperature, critical pressure, and acentric factor as characterization parameters and then tunes the binary interaction parameters between the components in the mixture to enhance the vapor-liquid equilibrium calculations. The results for vapor-liquid equilibrium calculations are sensitive to the values of these characterization parameters and binary interaction parameters in the cubic equation of state. For reservoir simulation studies, the detailed compositional model is usually replaced by a simplified model in which the compositional elements are lumped into a few groups of components rather than many individual components. This paper presents an internally consistent lumping scheme using a cubic equation of state for the translation of individual component critical temperatures, critical pressures, acentric factors, and binary interaction parameters between pure components into group critical temperature, critical pressure, acentric factor, and binary interaction parameters between lumped groups. Because the translation procedures are all internally consistent, the translated characterization parameters used in the cubic equation of state will minimize the loss of information from the lumping process.