Heavy oil and bitumen are composed of high molecular weight compounds, resulting in more viscous fluids than most conventional crude oils. For the production and transportation of such heavy fluids, it is necessary to reduce their viscosity. The dilution of such heavy fluids with liquid solvent is one of the practical methods to reduce the oil viscosity to the desired level.
In this study, a designed experimental apparatus has been set up to accurately measure the variations of viscosity and density for raw bitumen, aromatic solvents and bitumen/solvent mixtures under conditions applicable for both in situ recovery methods and pipeline transportation. The bitumen samples were taken from an Athabasca oil field, and the aromatic solvents were highly purified toluene and xylenes.
On the basis of the experimental results, the influences of pressure, temperature and solvent concentration on the density and viscosity of the raw bitumen and its pseudo-binary mixtures with aromatic solvents were considered. The experimental density and viscosity data for the solvents and for raw bitumen were then correlated using different correlations from the literature. The experimental density and viscosity data for the mixtures of Athabasca bitumen with toluene and xylenes were also evaluated with models representing certain mixing rules proposed in the literature.
The density data were well predicted with an equation that assumed no volume change occurs upon mixing. In contrast, the viscosity data of the studied conditions were well correlated with Lederer’s model and the power law model, both of which include one adjustable parameter. The comparison of the experimental and modeling results demonstrates that the calculated values of mixture density and viscosity showed slight deviations from the measured values at the highest temperature and highest solvent concentrations.