Quantification of Phase Behaviour and Physical Properties of n-Alkane Solvents/Water/Athabasca Bitumen Mixtures Under Reservoir Conditions

Abstract

Abstract Experimental and theoretical techniques have been developed to quantify phase behaviour and physical properties in terms of phase boundaries, swelling factors, phase volumes, and phase compositions. Experimentally, five sets of PVT experiments of pentane, hexane, and heptane, respectively, mixed with bitumen have been conducted to measure phase behaviour data in the absence and presence of water by using a conventional PVT setup at elevated temperatures up to 438.2 K. Theoretically, the Athabasca bitumen is characterized as four pseudocomponents, while the binary interaction parameters (BIPs) are optimized by reproducing the measured saturation pressures. The original Peng-Robinson equation of state (PR EOS) has been advanced to perform flash calculations by incorporating a recently modified alpha function and an improved volume translation method together with the Huron-Vidal mixing rule, while the results have been compared with those obtained from CMG WinProp module incorporated with the original alpha function as well as default and optimized BIP correlations. It is from the experimental observation that the saturation pressures of n-alkane solvents/water/bitumen mixtures are decreased with carbon numbers at the same conditions. Also, the saturation pressures of n-alkane solvents/bitumen mixtures are increased with the addition of water because water molecules are evaporated into vapour phase at relatively low pressure and high temperature conditions. The BIPs of pure solvent/bitumen pairs, which are optimized through fitting the measured saturation pressures, work well for n-alkanes/bitumen mixtures in the absence and presence of water. Such an advanced PR EOS (APR EOS) model can accurately reproduce the experimentally obtained multiphase boundaries, swelling factors, phase volumes and compositions with an average absolute relative derivation (AARD) of 7.82%, 2.11%, 6.78%, and 4.38%, respectively, indicating that it can provide fundamental data for the design and optimization of the hybrid solvent-steam recovery method for bitumen resources.