AN INTERNALLY CONSISTENT APPROACH FOR DETERMINING THE PROPERTIES OF LUMPED COMPONENTS USING A CUBIC EQUATION OF STATE

Cubic equations of state, due to their simplicity and accuracy, are co mmonly used in reservoir simulation to predict phase behavior of petro leum reservoir fluids. A cubic equation of state utilizes critical tem perature, critical pressure, and acentric factor as characterization p arameters and then tunes the binary interaction parameters between the components in the mixture to enhance the vapor-liquid equilibrium cal culations. The results for vapor-liquid equilibrium calculations are s ensitive 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 replac ed by a simplified model in which the compositional elements are lumpe d into a few groups of components rather than many individual componen ts. 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 binar y interaction parameters between pure components into group critical t emperature, critical pressure, acentric factor, and binary interaction parameters between lumped groups. Because the translation procedures are all internally consistent, the translated characterization paramet ers used in the cubic equation of state will minimize the loss of info rmation from the lumping process.