An improved vdW-type component mixing-rule applied in CO2-crude system

A new vdW-type mixing-rule has been proposed considering the interaction among the affecting factors of temperature, pressure and non-hydrocarbon components, through analysis of equation of state and theory of interaction among molecules. By the derivation of the formulation at reduced state, a new mixing-rule has been established for the conditions of high pressure and high temperature. The theoretical strictness of the rule has been demonstrated through reducing to the dependency relationship of second virial coefficients. With the in situ petroleum samples data of vapor and liquid phase components from actual measurement, comparison has been taken between the calculation precisions of components and densities parameters calculated by the new rule and the old one. The new mixing-rule has a better accuracy to meet the industrial requirement, and its calculation is also simplified. The weighted mean error of components calculation declines from 15% to 4% and that of density calculation from 10% to 3%.