Modelling Water-Hydrocarbon Mutual Solubility in Multiphase Equilibrium Calculations





Since the 1980s, multiphase equilibrium calculations have been well developed. Usually, water is excluded from the calculations although the amount of dissolved hydrocarbons and CO2 in water can be substantial. There are several published four-phase flash calculation methods using a single cubic EOS to model both hydrocarbon and aqueous phases, but the predicted gas solubility in water modeled from an EOS is orders of magnitude lower than experimental data. In this thesis, a generalized multiphase flash calculation algorithm is developed to address both the multiple phase behavior of a CO2/crude oil system and water-hydrocarbon mutual solubility simultaneously. The hydrocarbon phases are modeled with a cubic EOS, and the water phase is modelled with Henry’s law constants. Our results are compared with experimental data and calculation results from commercial software to validate the algorithm in different types of equilibria.