Pore-Scale Dynamics of Steam Assisted Gravity Drainage with Hydrocarbon Solvents (HC-SAGD) for Technically and Environmentally Efficient Heavy Oil Recovery

Steam Assisted Gravity Drainage (SAGD) is the primary in-situ heavy oil and bitumen recovery method in Canada. Improvement of the efficiency of this method is essential for new and matured SAGD projects to minimize the project cost and the amount of carbon emitted for steam generation. Adding hydrocarbon (HC) solvents to steam can effectively improve the recovery efficiency of SAGD by improving the recovery per amount of the steam used. The optimization of this process requires further clarifications and understandings on the fluid-steam-rock interactions, especially at the pore scale. For this purpose, a visual two-dimensional physical porous media model was constructed and HC additive-assisted SAGD (HC-SAGD) process was studied. Heptane was selected to represent the HC phase as it its boiling point is close to water. The effects of physicochemical properties of the oil-steam-water-heptane and fluid-rock interactions on the growth of the steam chamber and oil drainage were visually analyzed. The oil recovery efficiency, energy efficiency and carbon emission intensity of HC-SAGD and SAGD were compared for different scenarios to suggest optimal operational conditions. It was shown that the introduction of HC can reduce carbon emission intensity to that of the half of conventional SAGD while improving heavy oil recovery. It was also observed that the technical and economic benefits of solvent addition to steam in the SAGD process could be much higher than previously anticipated.