Study on CO2–Water Co-Injection Miscible Characteristics in Low-Permeability Near-Critical Volatile Oil Reservoir

Low-permeability near-critical volatile reservoirs are characterized by light oil, complex fluid phase, and strong reservoir inhomogeneity, etc. Purely injecting CO2 will create a series of problems, such as serious gas channeling, low sweep efficiency, oil recovery. Therefore, in this paper, through combination experiments simulations the process studying problem from simple to complex, we carried out phase equilibrium for CO2-near-critical oil-formation water, well minimum miscible pressure slim-tube with pure CO2–water co-injection comparative study characteristics displacement efficiency between injection co-injection. It provides an important reference improving recovery low-permeability reservoir. The results oil/CO2-near-critical water show that saturation pressure, density, gas–oil ratio system increase, viscosity decreases increase injection. In three-phase content flash crude ratio, gas–water negatively correlated saturation. on degree under is higher than injection, dissolved transition section shorter breakthrough time later co-injection, which effectively increases improves oil. When higher, rises, breakthrough, indicates when more inhibits occurrence channeling area, thus research paper provide experimental basis theoretical foundation enhanced reservoirs.