Measuring diffusion coefficients of gaseous propane in heavy oil at elevated temperatures

Molecular diffusion is an important phenomenon for solvent transport during vapor extraction and hot solvent injection into heavy oil reservoirs. Therefore, determining solvent diffusion into heavy oil is important for predicting oil recovery. We conduct soaking tests at different temperatures ranging from 80 to 130 °C to estimate diffusion coefficient of propane (C 3 H 8 ) into heavy oil samples taken from Clearwater Formation in the Western Canadian Sedimentary Basin. The tests are conducted at the maximum initial pressure of 1900 kPa to keep C 3 in vapor phase within the tests’ temperature range. Pressure decline during the soaking process is analyzed to estimate diffusion coefficients and solubility of propane in the oil at equilibrium conditions. The final viscosity of the mixture is also calculated by using the available correlations. The results show that diffusion of propane in heavy oil undergoes three different stages: early region, transition region, and late-time region. The maximum diffusion coefficient is observed at the end of transition region. Solubility of C 3 in the oil increases with decreasing temperature. The results also reveal that during the three regions, solubility and diffusion coefficients of C 3 into the oil strongly depend on temperature.