Role of Bitumen-Water Interfacial Tension in Steam Assisted Bitumen and Heavy Oil Production; Solvent versus Surfactant Coinjection with Steam Processes

ABSTRACT: Over 80% of Athabasca, Alberta, Canada oil sands deposits are suitable for bitumen production by thermal in-situ recovery processes, such as SAGD and CSS processes; by which bitumen is produced over 1,500,000 barrels/day capacity. Oil industry needs novel methods to improve thermal efficiency, improve profitability and reduce environmental footprints of these processes. For this purpose, solvent (light hydrocarbons) co-injection with steam is studied by oil industry, speculating that it would reduce bitumen viscosity and increase bitumen mobility as predicted by Darcy’s Law; which resulted in limited commercial success. Interestingly, these studies neglected the effect of solvent on bitumen-water interfacial tension. At our laboratory, surfactant, such as biodiesel (fatty acid methyl esters) co-injection with steam is being developed as an alternative method to solvent co-injection with steam process. Steam assisted bitumen recovery tests were operated in continuous and batch (pressure cooker) modes, and high temperature-high pressure bitumen-water interfacial tension measurements were performed using pending drop method. Core samples from SAGD reservoirs, bitumen and process affected water recovered from bitumen-water emulsions produced by SAGD processes which were untreated with any chemical additive, were used in these tests. Bitumen recovery tests were made by operating the test unit as a pressure cooker, and showed that pentane addition into steam, at 5% and 15% of bitumen mass, reduced bitumen recovery efficiency by 39% and 61%, respectively, which contradicts expectations of solvent co-injection EOR methods. Our research findings suggest that solvent co-injection with steam further decreases bitumen viscosity, which is already reduced by thermal heating, but increases bitumen-water interfacial tension and causes slip of water at bitumen-water interface; which results in increase in water and decrease in bitumen mobilities. Experimental data on surfactant behavior of biodiesel and mathematical analysis of two phase immiscible fluids flow with slip boundary condition at bitumen-water interface will be discussed.