Improved Experimental and Mathematical Techniques for Measurement of Solvent Gas Diffusivity in Heavy Oils

Efficient recovery of heavy oil and bitumen is still very challenging and remains an issue of ongoing research all around the world. Thermal recovery methods, which rely on heat for viscosity reduction, are generally accepted as viable and several steam based projects have been successful, especially in Canada. Using light hydrocarbon solvents can provide similar viscosity reduction and is potentially more efficient in so-called challenging reservoirs where thermal methods do not work. In comparison with thermal methods, solvent based processes are more environmentally friendly and require no fresh water resources.;The solvent based processes rely on molecular diffusion for in situ mixing of the solvent with the oil and generally provide much slower rates of oil production than the thermal processes. This is so because the molecular diffusivity is often much smaller than the thermal diffusivity. However, the published information on experimentally determined diffusivity of gaseous solvents in heavy oil and bitumen is very scarce. Therefore, accurate measurement of molecular diffusion coefficient is necessary for reliable design of solvent-based recovery processes in heavy oil reservoirs.;There is no well-established and universally applicable technique for measuring molecular diffusion coefficient. Measurements of mass transfer characteristic are often more difficult due to difficulties in measuring point values of concentration and other issues which complicate this transport process such as phase equilibrium, effect of convective transport and having a mixture rather than a pure fluid. These issues make it necessary to employ several simplifying assumptions in mathematical modeling and interpreting the experiments to determine the diffusivity.;The focus of this thesis is on improvement of experimental and mathematical techniques for measurement of unknown mass transfer parameters, specifically molecular diffusion coefficient, in dissolution of gaseous solvents into bitumen in binary systems. This is accomplished through identification of different phenomena or states occurring during the diffusion of gaseous solvents into bitumen and accordingly, development of improved experimental technique, mathematical models and computational algorithms for different cases. Diffusion coefficient of methane, carbon dioxide and propane were estimated as gaseous solvents diffusing into bitumen and it was shown that the estimated parameters generally agree with those reported in the literature.;The outcome of this study is directly relevant to the in situ recovery of heavy oils and bitumen; however, the proposed techniques could also be applied to other applications for determination of diffusivity of gases dissolving into non-volatile liquid systems.