IMPROVING PREDICTIONS OF EQUATION OF STATE BY MODIFYING ITS PARAMETERS FOR SUPER CRITICAL COMPONENTS OF HYDROCARBON RESERVOIR FLUIDS

The parameters of equations of state of van der Waals type have been g enerally correlated by matching the properties of pure substances, and extended to mixtures by employing mixing rules commonly with binary i nteraction parameters. It is proposed to use equilibrium data on binar y systems to determine the attraction term in equations of state (EOS) for super critical components instead of data of pure substances. The proposed method was applied to the Peng-Robinson EOS, as an example, resulting in a significant improvement in predicting the phase behavio ur of different types of fluids. As no binary interaction parameters a re required in this method the computational requirement for flash cal culations is drastically reduced for fluids with many components. The proposed method is particularly advantageous for predicting fluid phas e equilibria in compositional reservoir simulators, where the reservoi r fluid can be described with any desirable number of components witho ut any significant increase in computational time.