In this paper, the complicated displacement mechanisms of injection of CO2, surfactant and steam into heavy oil reservoirs are evaluated using a laboratory physical model and a numerical simulation model. There are four different recovery scenarios examined, which include steam-only injection, steam injection with CO2, steam injection with surfactant and steam injection with CO2 and surfactant. The incremental recoveries of different scenarios are compared and analyzed. The effect of CO2 dissolution in oil and water, variation of properties of CO2-oil phase equilibrium and CO2-water phase equilibrium, variation of viscosity, oil volume and interfacial tension (IFT) during the recovery process are investigated. The expansion of steam and CO2 front is also examined. A field application case of a horizontal well in a heavy oil reservoir in Shengli Oilfield, China is studied. The actual dynamic performance of the horizontal well with cyclic injection with steam, CO2 and surfactant is analyzed and the injection parameters are optimized. The results show that in spite of immiscible drive of CO2, CO2 dissolution in oil helps to improve flow performance of heavy oil. At the same time, while CO2 is simultaneously injected with steam, it decreases the temperature of steam front to some extent compared with steam injection only, which has an effect on the expansion of steam chamber. Viscosity reduction, swelling and IFT reduction play important roles in improving recovery factor of heavy oil reservoirs. K values of CO2-oil and CO2-water phase equilibrium vary with reservoir pressure and temperature, which have an effect on displacement process. In laboratory model the oil recovery of the simultaneous injection of steam, CO2 and surfactant is higher than that of others. In the field application case the optimal design of injection parameters helps achieve the highest recovery.

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