Mixing of solvent and bitumen in steam-solvent co-injection under controlled thermodynamic conditions

The most important aspect of solvent-aided steam-assisted gravity drainage (SA-SAGD) is the interplay between phase behavior and fluid flow near the edge of a steam chamber, which is caused by the mixing of solvent with bitumen. The mixing of solvent with bitumen (i.e., dispersion) results in dilution of the bitumen and improves the energy efficiency of SAGD. However, it is often difficult to analyze this through large-scale steam injection experiments because chamber-edge thermodynamic conditions in the experiments are transient. Moreover, research studies on dispersion, along with dispersion coefficient data, in SA-SAGD are scarce. This thesis presents a novel small-scale experimental method and a numerical model designed to study the bitumen gravity drainage with steam injection (SAGD) and solvent-steam co-injection (SA-SAGD) under controlled thermodynamic conditions, such as pressure, temperature, and composition. The dispersion coefficients for solvents with bitumen under gravity drainage with controlled boundary conditions are determined by calibrating a fine-scale numerical model with experimental data. The experiments use a 3-inch diameter by 15-inch length sand-pack placed in a 25-L cylindrical pressure vessel. The sand-pack is surrounded by a one-inch annular void space, into which the vapor phase is injected under controlled pressure, temperature, and composition. Both steam only and steam and solvent co-injection experiments are performed at a pressure of 3500 kPa. Oil production and temperature profiles inside and outside the sand-pack are recorded for all experiments. Post excavated samples from the sand-pack are analyzed. The results of the SAGD base case are history-matched using a numerical simulation model. The established parameters from the SAGD history match are then transferred to the SA-SAGD simulation model. The SA-SAGD experiments are history matched by fine-tuning the dispersion coefficient to better model the mixing between the solvent and bitumen. The dispersion coefficient for C₄ and C₈ in bitumen for SA-SAGD are determined to be 5.83×10⁻² m²/day and 5.64×10⁻² m²/day, respectively. The associated Péclet numbers for C₄ and C₈ dispersion coefficients are 60 and 309. The solved dispersion coefficients are analyzed and discussed. Finally, the criteria and guidelines are given for applying the determined dispersion coefficients in the field-scale simulation of SA-SAGD.Petroleum and Geosystems Engineerin