Prediction of the solubility and gas-liquid equilibria for gas-water and light hydrocarbonwater systems at high temperatures and pressures with a group contribution equation of state

A group contribution equation of state has been proposed. The model is based on the Weidlich-Gmehling modified UNIFAC and Soave-Redlich-Kwong equation of state, in which the modified Huron-Vidal excess Gibbs free energy mixing rule is used, the residual term of the modified UNIFAC is changed a little and the combinatorial term is improved. Nine interaction parameters between gas groups CO2, CO, N2, H2, H2S, CH4, C2H6, C3H8, C4H10 and water are fitted. The model parameters have been used to predict solubility and gas-liquid equilibria for seven gas-water, and thirty-nine light hydrocarbonwater data sets in large temperature and pressure ranges (278–637 K, 1–1972 bar). The predicted results are in good agreement with the experiments, which makes it possible that the real phase behavior at high temperatures and pressures for gas-water and light hydrocarbonwater systems which are of interest to petroleum and natural gas exploitation industries, can be predicted reliably.