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 k(ij) 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. (C) 2012 Elsevier B.V. All rights reserved.