A model for single-phase PVTx properties of CO2–CH4–C2H6–N2–H2O–NaCl fluid mixtures from 273 to 1273 K and from 1 to 5000 bar

A thermodynamic model explicit in Helmholtz free energy is constructed to calculate the single-phase PVTx properties of the CO2–CH4–C2H6–N2–H2O fluid mixtures. Parameters of the binary CO2–H2O, CH4–H2O, C2H6–H2O and N2–H2O mixtures are regressed from assessed experimental data. On the basis of the binary mixture parameters, the model can be used to predict the single-phase volumes of the CO2–CH4–C2H6–N2–H2O–NaCl fluid mixtures with a simple approach. Comparison with a large number of experimental data shows that the model can reproduce the single-phase PVTx properties of the CO2–CH4–C2H6–N2–H2O–NaCl fluid mixtures from 273 to 1273 K and from 1 to 5000 bar, with or close to experimental accuracy. Online calculations can be made on the website: www.geochem-model.org/.