CO₂ flooding technology for enhanced oil recovery in tight oil reservoirs: A review

Tight oil is recognized as an important unconventional hydrocarbon resource. However, the exploitation of tight oil reservoirs faces serious challenges due to their low porosity and permeability, and conventional methods often yield low oil recovery in these reservoirs. Therefore, enhancing oil recovery in tight oil reservoirs has become a key research focus. CO₂ flooding can significantly improve oil mobility and further enhance oil displacement efficiency, representing a mature technology for enhanced oil recovery. Primary mechanisms behind this technology include viscosity reduction (by 50%−80%), oil volume expansion (volume expansion factor: 1.19‒1.53), miscibility, and improvement in wettability. Given that the low permeability of tight oil reservoirs and CO₂ channeling frequently lead to poor oil displacement effects, researchers have proposed various composite technologies, including chemically and physically assisted technologies, CO₂ foam flooding, and gravity-assisted CO₂ flooding. This study reviews the current status and development trends of composite CO₂ flooding technologies for tight oil reservoirs, analyzes their challenges and solutions, and proposes future research directions. The results of this study provide a reference for enhancing the productivity of tight oil reservoirs.