Advances in diffusivity and viscosity measurements of hydrocarbon solvents in heavy oil and bitumen.

摘要

The solvent based recovery process VAPEX has a great potential for the recovery of heavy oil and bitumen resources, due to the low energy consumption and reduced green house gas emission associated with this process compared with other EOR techniques. Molecular diffusion and dispersion of solvents into heavy oil are important physical parameters governing VAPEX or any solvent based EOR process. Therefore an accurate estimation of the diffusion of hydrocarbon solvents in heavy oil is essential for calculating the rate of solvent dissolution in bitumen and heavy oil.; The aim of this research is to study diffusion and change of viscosity in hydrocarbon solvent-heavy oil systems. Low field magnetic resonance is used to determine diffusion coefficient of solvents into heavy oil and bitumen and it is also used to monitor changes in the viscosity of mixtures of heavy oil with hydrocarbon solvents.; As the solvent comes into contact with the bitumen-sand matrix, it gradually diffuses into the liquid-filled pores and dilutes the bitumen. NMR spectra are continuously acquired for the duration of each diffusion test. The changes in solvent and bitumen concentrations are detected through changes in the NMR relaxation characteristics of the sample. Diffusion coefficients are generated through a mass transfer model based on second Fick's law and is compared to diffusion of solvent into bulk heavy oil. The novelty of the presented approach is not only that the new model matches all the experiments to date, but also that this matching can be done independently and without external input parameters. In previous work matching could only be achieved if the depth of solvent penetration was provided through external measurements. It is anticipated this method would be of value when estimates of mass transfer in solvent based heavy oil processes are attempted in the field.; It was also stablished the viscosity of the mixture of heavy oil and solvents can be predicted using two different models, Shu model and NMR model. Both models showed a close match with the actual viscosity measurements. This would enable in-situ monitoring of changes in the viscosity of heavy oil in solvent based EOR processes.