Prediction of vapor–liquid equilibrium for reservoir mixtures with cubic equations of state: Binary interaction parameters for acidic gases

Only recently acidic gas mixtures have received more attention, since the exploitation of reservoirs whose fluids may have very high concentrations of both CO2 and H2S has started being taken into consideration, in spite of the risks and technical difficulties in dealing with these fluids. But present huge energy demand, coupled with technological achievements, has allowed to include these “unfriendly” fluids among the possible energy sources. Experimental data on H2S are much more recent and limited with respect to those on CO2, since higher risks and ad hoc required experimental apparatus had prevented the experimentation.For the prediction of vapor–liquid equilibrium of reservoir mixtures, dedicated commercial software uses cubic equations of state (SRK, PR) in the original form, i.e. with classical quadratic mixing rules, since they do not present appreciable deviations from experimental data and are not demanding as for computational time. Optimized values of the binary interaction parameter kij for CO2 and H2S with a wide class of hydrocarbons is presented since a lack of such parameters in databanks of reservoir and process simulation packages has been detected.

► Vapor–liquid equilibrium estimates are improved.
► Optimal binary interaction parameters for SRK and PR are obtained.
► A new correlation for the estimation of kij is proposed.
► Mixtures of CO2 or H2S with hydrocarbons are taken into account.
► The method is verified to VLE estimation of ternary mixtures.