Phase Equilibria of Hexane/Water and Hexane/Water/Bitumen Systems with Applications to Solvent-Aided Thermal Recovery Processes of Bitumen

Abstract

This thesis presents an experimental study of the phase equilibria of hexane/water and hexane/water/bitumen mixtures applicable to solvent-assisted thermal recovery processes. The solvent selection for solvent-aided thermal recovery processes is often chosen based on the proximity of solvent saturation properties to steam. In this thesis, such a premise is examined by evaluating the phase equilibria of hexane/water and hexane/water/bitumen mixtures to fill the existing knowledge gap and draw a conclusion on the validity of such a hypothesis.First, a PVT setup was used to measure the vapor-liquid equilibria (VLE) of hexane/water binary mixtures at temperatures ranging from 183-215 °C and a constant pressure of 2.5 MPa. The results indicate an azeotropic behavior with a co-condensation temperature of 183.7 °C at a hexane mole-fraction of 0.6029. The Cubic Plus Association Equation of State (CPA-EoS) and activity coefficient-based Non-Random Two Liquid (NRTL) models were used to model the measured experimental data, and the predicted results are in good agreement with the measured data. Next, the condensation properties of a solvent/water mixture in the presence of Mackay River Bitumen (ternary system) were performed. The phase behavior, viscosity, and density measurements were taken at two typical mole fractions of solvent (1 and 5%) in the steam/solvent mixture while keeping the hexane/bitumen ratio constant at temperatures ranging from 183-215 °C and a constant pressure of 2.5 MPa. The results revealed a vapor-liquid-liquid equilibrium (VLLE). The phases in equilibrium include a vapor phase consisting of hexane and water, a liquid phase comprising hexane/water bitumen, and a second liquid phase containing hexane/water. The condensation trends of the binary hexane/water and ternary hexane/water/bitumen systems were compared. The results revealed that the hexane concentration in the ternary systems is close to those of the binary mixture at any given temperature, suggesting that the binary system of solvent/water may be used for condensation studies. In addition, the results revealed that the solubility of hexane in bitumen dominates viscosity reduction at the temperature range of interest. The cubic-plus-association equation of state (CPA EoS) was used to model the phase equilibria of hexane/water and hexane/water/bitumen mixtures. The findings provide insight into steam/solvent condensation behavior with applications to the solvent-aided thermal recovery of bitumen from oil sands.