Abstract:

CO₂ flooding is a technique that utilizes CO₂ to enhance oil recovery (CCUS-EOR), and an effective means to reduce carbon emissions. To understand the interphase mass transfer in the petroleum system during CCUS-EOR, CO₂/dry gas contact experiments were conducted to elucidate the changes in components of the petroleum system during the initial contact conditions at different pressures. The results indicate that during the initial contact between CO₂ and oil, the interphase mass transfer for volatile and non-volatile components occurs through evaporative extraction, while the interphase mass transfer for intermediate components occurs through dissolution diffusion, which is stronger than evaporative extraction. As pressure increases, the volatile components show enhanced evaporative extraction, the non-volatile components reflect diminished evaporative extraction, and the intermediate components exhibit augmented dissolution diffusion. At relatively low pressure in the initial stage of gas injection, the interphase mass transfer of the petroleum system is dominated by evaporative extraction. As pressure increases, the mechanism of interphase mass transfer for volatile components shifts to dissolution diffusion. During the initial contact process between dry gas and oil, the interphase mass transfer for intermediate and non-volatile components is dominantly evaporative extraction. CO₂ is more capable of evaporative extraction than dry gas.

Key words: CCUS-EOR, initial contact, evaporative gas flooding, condensate gas flooding, evaporative extraction, dissolution diffusion