Phase diagrams for binary mixtures of H2S + n-alkanes, H2S + CO2, CO2 + CH4 and a ternary mixture containing H2S, CH4 and CO2 are determined with atomistic simulations. Pressure-composition diagrams for each of the binary mixtures are determined with configurational-bias Monte Carlo simulations in the grand canonical ensemble, combined with histogram-reweighting techniques. Overall, the predicted phase diagrams for the H2S + n-alkanes and CO2 + CH4 mixtures are found to be in excellent agreement with experiment, while significant deviations are found between simulation and experiment for the H2S + CO2 mixture. Gibbs ensemble Monte Carlo simulations are used to determine the ternary phase diagram for the H2S + CH4 + CO, mixture at 310.93 K and 41.3 bar. Comparison of simulation to experiment shows a close agreement at the temperature and pressure studied in this work. (c) 2006 Elsevier B.V. All rights reserved.