Improvement of SRK equation of state for vapor-liquid equilibria of petroleum fluids

To improve the SRK equation of state for the calculation of vapor-liquid eq uilibria of petroleum fluids, the parameters of the Mathias-Copeman alpha-f unction were refitted to a large number of experimental vapor-pressure data (15,311 data points) stored in the Dortmund Data Bank with a particular vi ew to improving the accuracy of the vapor-pressure correlation in the low p ressure range. Using the new parameters, vapor-liquid equilibria were calcu lated using two different mixing rules: the group contribution mixing rule for the mixture parameters a of the SRK EOS; the conventional mixing rules for the mixture parameters a and b of the SRK EOS together with a character ization method developed on the basis of existing empirical correlations fo r the properties of plus fractions of undefined mixtures. The results show that the accuracy for crude oil and natural gas mixtures can be improved by refitting the SRK EOS parameters.