The phase behaviour and thermo-physical properties of bitumen/solvent systems are of crucial importance for heavy oil and bitumen in-situ recovery methods as well as pipeline transportation, surface upgrading, and refining. The equilibrium properties of mixtures containing heavy oil are also important for the development of numerical simulators, the application of various thermal and non-thermal recovery processes, and the application of fluid extraction processes.
The main objective of this study was the development of a comprehensive understanding of the phase behaviour of bitumen/solvent mixtures. A new pressure-volume-temperature (PVT) apparatus was designed and constructed to acquire experimental data for the phase behaviour of bitumen/solvent mixtures and their thermo-physical properties. A new methodology for phase detection and accurate volume measurements was proposed for obtaining single liquid, vapour-liquid, and liquid-liquid equilibrium properties as well as the extraction yield for bitumen/solvent systems.
New vapour-liquid and liquid-liquid equilibrium data for Athabasca bitumen / ethane and Athabasca bitumen / propane mixtures were experimentally acquired and corresponding phase diagrams were generated over wide ranges of temperatures and pressures. The effect of different parameters, such as the solvent-to-oil ratio, pressure, and temperature, on equilibrium phase compositions, saturated phase properties (density and viscosity), and the distribution of fractions in different phases were studied. The optimal solvent for bitumen viscosity reduction was identified at different operating conditions. The potential applications of ethane and propane for the supercritical and subcritical extraction of valuable components from bitumen were also experimentally evaluated. The generated data were then modelled with the Peng-Robinson equation of state to accurately predict the phase boundaries and phase compositions.
New measurements for thermo-physical properties of Athabasca bitumen / n-hexane and Athabasca bitumen / condensate mixtures were conducted at different temperatures, pressures, and solvent weight fractions. The mixture density and viscosity data were evaluated with predictive schemes as well as with correlation models representing certain mixing rules proposed in the literature. The influences of pressure, temperature, and solvent weight fraction on the density and viscosity of mixtures were considered in the models and evaluated from the experimental results.