MECHANISMS AND TECHNOLOGICAL ADVANCES OF CO₂ FLOODING FOR ENHANCED OIL RECOVERY

In recent years, carbon dioxide flooding has garnered widespread attention as an important technique for enhancing oil recovery in both conventional and low-permeability reservoirs. This method involves injecting CO₂ into the reservoir, where it interacts with crude oil through mechanisms such as oil swelling, viscosity reduction, and miscibility, thereby improving oil mobility and establishing effective displacement pathways to increase recovery. As the efficiency of conventional water flooding continues to decline, CO₂-EOR is increasingly regarded as a viable technological option for enhancing the development of mature oilfields, with additional benefits for engineering and environmental synergy. This paper provides a systematic review of the mechanisms and injection strategies associated with CO₂-EOR. Emphasis is placed on the phase behavior of CO₂ and its interactions with crude oil, including key controlling factors such as oil swelling, viscosity reduction, phase behavior evolution, and minimum miscibility pressure. The applicability and technical characteristics of different injection schemes are compared and discussed. Furthermore, using independently developed multi-field coupling simulation software, a representative CO₂ flooding model was constructed. The spatiotemporal evolution of physical fields and fluid components during injection was analyzed in detail, validating key mechanisms and the production enhancement potential of CO₂-EOR. Finally, this study systematically evaluates challenges including reservoir heterogeneity, gas channeling risks, and injection safety during CO₂-EOR operations, and assesses the potential for synergistic implementation of CO₂-EOR and carbon sequestration. The results aim to offer theoretical support and technical guidance for future research and field applications.