The main objective of this research is to study the diffusion process of liquid and gaseous solvents in heavy oil and bitumen, with the aim of obtain the diffusion coefficient. The diffusion of n-hexane, n-heptane and octane in liquid phase and the diffusion of gaseous propane and carbon dioxide was monitored using x-ray computed tomography.
The concentration and density profiles were obtained from the x-ray measurements and the data was used as entry for the slopes and intercepts model and for the non-iterative finite volume method to obtain the diffusion coefficients. The results show a strong dependency of the diffusion coefficient on the concentration of solvent in the system. The data obtained agree with the literature of less complex systems. The diffusion of carbon dioxide differs from the diffusion of hydrocarbon solvents. The diffusion coefficient can be both, an increasing or decreasing function of concentration depending on the nature of the diffusing solvent.
Predictions of the diffusion coefficients of the systems studied here were also performed using the Vignes model. The model successfully predicts the diffusion coefficient for hydrocarbon solvents in heavy oil. However the accuracy of the Vignes equation diminishes as the viscosity of the oil phase increases.
The results of this study can be applied in the simulation and understanding of the solvent based enhanced recovery processes for heavy oil and bitumen reservoirs.