A comprehensive review of minimum miscibility pressure determination and reduction strategies between CO2 and crude oil in CCUS processes

Miscible CO2 injection is a crucial Enhanced Oil Recovery (EOR) technique that not only improves sweep efficiency and eliminates CO2-oil interfacial tension-resulting in up to 10% higher oil recovery compared to immiscible flooding-but also contributes to environmental sustainability by reducing greenhouse gas emissions through Carbon Capture, Utilization, and Storage (CCUS). Achieving the Minimum Miscibility Pressure (MMP) is critical for the success of miscible CO2 injection, as it ensures the merging of oil and gas phases into a single phase, thereby maximizing oil recovery. In this paper, we thoroughly review experimental and computational methods used to determine MMP between CO2 and crude oil. We analyze 11 experimental setups and synthesize findings from extensive literature, comparing their benefits and limitations. Experimental data measured by different experimental methods is also collected. Additionally, we evaluate computational approaches for MMP calculation, including correlation-based and Equation of State (EOS) methods. However, miscible displacement may not be feasible in all reservoirs, particularly those with high temperatures that require injection pressures exceeding formation fracture pressures. Consequently, this study also examines strategies to adjust gas injection pressure and composition, thereby reducing MMP, and evaluating their practical and economic feasibility. This comprehensive review aims to deepen the understanding of MMP and its pivotal role in optimizing CO2 flooding and other miscible gas injection strategies, supporting both enhanced oil recovery and carbon sequestration initiatives.