Effect of the Presence of Sand on Solvent Diffusion in Bitumen
Afsahi, B. and Kantzas, A.
CIM 2005-092 presented at the 56th Annual Technical Meeting of the Petroleum Society held in Calgary, June 7-9, 2005.
Mass transfer mechanisms in VAPEX and estimation of diffusion and dispersion coefficients of solvents into bitumen are popular subjects in heavy oil and bitumen research. In previous work, it was shown that low-field NMR could be used as a useful tool in determining diffusion coefficients of solvent into bitumen. The present paper extends this previous work into new areas as follows: First, the effect of the presence of sand on diffusion coefficient measurements is studied. This is done by mixing sand and Cold Lake bitumen and exposing it to a liquid solvent. 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 different mass transfer models and are compared to sand-free data that were presented previously.