Phase Behavior Study of Hydrocarbon-Water-Alcohol Mixtures

Experiments were performed to study the phase behavior of gas condensate hydrocarbons at reservoir conditions. Constant composition measurements were done on synthetic gas condensate mixtures and the results were used to regress the Peng-Robinson equation-of-state with the temperature-dependent Peneloux volume corrections and classical van der-Waals mixing rule (PR78 Peneloux (T)). Experiments were performed to study the effect of water and methanol on the phase behavior of gas condensate hydrocarbons. Effects of various factors including temperature, pressure and the molar concentrations of water and methanol on the phase behavior of hydrocarbon-water-methanol mixtures were studied. Addition of methanol increased the liquid volume fraction and the dew point pressure when added to the hydrocarbon mixture. However, for hydrocarbon-water-methanol mixtures the aqueous phase volume fraction increased while the dew point pressure decreased with increasing mole fraction of methanol. PR78 Peneloux (T) equation of state was used to model hydrocarbon-water-methanol mixtures. The EOS was regressed to match the experimental data by tuning the binary interaction coefficients between components and their volume shift parameters. The mixtures were also modeled using Peng-Robinson equation of state with temperature-dependent Peneloux volume shift correction factors and Huron-Vidal mixing rules (PR78 Peneloux (T)-HV). The calculations from both the EOS models agree quantitatively with the experimental results. The binary interaction parameters were found to be temperature dependent. The binary interaction parameters and the temperature-dependent volume shift parameters are the key parameters to model these complex mixtures using any EOS model. The multiphase flash capability of PVTSim software by Calsep Inc. was used to calculate the phase diagrams since the phase behavior is sometimes three-phase liquid-liquid-vapor under the experimental conditions. Phase behavior experiments were also performed on hydrocarbon-water-iso-propanol (IPA) mixtures to investigate the effects of iso-propanol on the phase behavior of gas condensate hydrocarbons. The results show that IPA decreases the aqueous phase volume fraction and increases the liquid hydrocarbon phase volume fractions when compared to the analogous hydrocarbon-water-methanol mixtures. Finally, the effect of fluorosurfactants FC4432 and S10 on the phase behavior of gas condensate hydrocarbon-water-methanol mixtures was studied experimentally.Petroleum and Geosystems Engineerin