Phase Behavior and Physical Property Modeling for Vapex Solvents: Propane, Carbon Dioxide, and Athabasca Bitumen

Abstract

Abstract Employing CO2 as the non-condensable gas in the Vapex process is an attractive option that could provide environmental benefits of CO2 sequestration along with improved Vapex performance. Mixtures of CO2 and a hydrocarbon such as propane allow the solvent to be tailored to different reservoir conditions. To test potential solvent mixtures, the phase behavior and physical properties measurements and modeling are required. We have previously reported on the phase behavior, viscosity and density of the CO2-propane-Athabasca Bitumen systems (Badamchi-Zadeh et al., 2009a,b). These results confirmed the ability of carbon dioxide and propane mixtures to sufficiently reduce Athabasca bitumen viscosity. In this study, an oil characterization and equation of state model are developed to describe the phase behaviour of mixtures of carbon dioxide, propane, and Athabasca bitumen. The model is tuned to fit the experimental phase behaviour data for binary and ternary mixtures of these components. Solubility data for carbon dioxide and Athabasca bitumen reported by Svrcek and Mehrotra 1982 are also used. It was found that two parameter cubic equation of state would require a third parameter (i.e. volume-shift) to better predict liquid density. The volume shift parameter was adjusted to improve cubic equation of state calculated liquid density against experimental data. Pederson (1987) viscosity correlation coefficients were modified to improve liquid viscosity prediction for propane, carbon dioxide, and bitumen mixtures.