M. Karimnezhad - Shahid Bahonar University of Kerman, Iran
Z. Kouhian

There are some methods to determine equilibrium ratios of different components of a vapor liquid equilibrium,including K-value charts, ideal solution principle, empirical correlations, equations of state and so on. In this paper, different ranges of pressures and temperatures which petroleum reservoir hydrocarbonmixtures might experence are simulated by using Mixprops software and its result are compared to choose the most accurate method to determine equilibrium ratio at a given condition. Among all of these methods, using equations of state such as Peng-Robinson EOS andSoave-Redlich-Kwong EOS gives the most accurate results which are the closest values to practical measurements of K-values, thus the accuracy of eachmethod is determined by comparison of its results with the most accurate method, EOS. Only light paraffin hydrocarbons from methane to hexane and heptane plusfraction and also N2, CO2 and H2S are considered as impurities. Finally the effect of changes of pressure, temperatureand composition of K-value and the best method to obtain K-value with the lowest error is determined.