Numerical Evaluation of CO₂, Water, and Combined CO₂–Water Injection for Enhanced Oil Recovery and Carbon Storage in Shale Reservoirs

Under the global carbon neutrality goal, achieving synergistic benefits between enhanced oil recovery and geological CO₂ sequestration in shale reservoirs is of great significance. In this study, we constructed a numerical simulation model based on the geological settings of the Jiyang Depression in the Shengli Oilfield to investigate the performance of three injection strategies: water injection, CO₂ injection, and combined CO₂–water injection. The simulations evaluated the evolution of reservoir pressure, oil saturation, CO₂ saturation, and water saturation over time. Results show that CO₂ injection offers the highest oil recovery and carbon storage potential, while co-injection exhibits a balance between injection stability and displacement efficiency. Compared with previous studies, this work provides a systematic and comparative analysis of multi-scheme injection performance, offering new insights into the optimization of EOR strategies and carbon storage in shale formations. The findings contribute to the theoretical foundation for the efficient development of unconventional resources under low-carbon constraints.