Evaluation of Diffusion of Liquid Solvents in Bitumen and Heavy Oil Using the X-Ray Tomography Technique

Abstract

The overall goal of this study was to conduct a series of diffusivity experiments between liquid hydrocarbons (propane and pentane) and Canadian bitumen and heavy oil in order to attempt to determine the role of different factors such as asphaltene precipitation and settling, among others, in these mass transfer processes. An apparatus was constructed and commissioned to measure the mass transfer in these systems based on the density profiles established over time in aluminum vessels containing a column of solvent over bitumen/heavy oil. The vessels were scanned regularly using a CT-Scanner in order to track the behavior of the density profiles over time, the liquid-liquid mass transfer data were collected and analyzed, obtaining interesting results, which will be important as a starting point for future research related to systems that integrate interactions between solvents and oils in recovery processes as VAPEX. This research is unique due to the obtained results; one of the findings, which was never published in previous literature, was the partial miscibility when mixing n-propane and bitumen, and another results to highlight are the oil swelling, oil shrinkage, asphaltene precipitation and settling, fully miscibility, and the effect of adding pure asphaltenes and calcium carbonate to the mixture, among others. It was found that partial miscibility was not manifested for all the cases (this condition occurred in cases when solvents and oils were mixed at certain solvent fractions). It was determined that oil is the controlling factor in the diffusion process when partial miscibility exists. Diffusion coefficients were calculated for all cases, and it was determined that diffusion is concentration dependent.