Mechanism of Oil Displacement by CO₂ and Chemical Agent Flooding in Low-Permeability Glutenite Reservoirs

Low-permeability glutenite reservoirs exhibit significant heterogeneity, which complicates waterflooding development, results in relatively low recovery rates, and increases the likelihood of gas channeling during gas flooding. A pressing need exists to investigate enhanced oil recovery (EOR) methods specifically suited for low-permeability glutenite reservoirs. The oil displacement mechanism of CO₂ flooding combined with chemical agent flooding was elucidated using the X oil reservoir as a case study. An experiment was conducted to measure the interfacial tension of CO₂ flooding, followed by an assessment of the interfacial tension of chemical agent flooding, with a long-core experiment performed to evaluate the enhanced oil recovery performance of CO₂ and chemical agent flooding. The results demonstrate that as formation pressure increases, the interfacial tension between CO₂ and crude oil decreases, with a further reduction observed as the degree of mixing increases. The interfacial contact angle is lowered, and interfacial tension is reduced by altering the wettability of the reservoir. The oil displacement efficiency is maximized when 0.4 HCPV chemical slugs are combined with CO₂ injection. Appropriate chemical slugs inhibit gas channeling and extend the distribution range, thereby enhancing displacement efficiency. A theoretical foundation for the efficient development of low-permeability glutenite reservoirs is provided, with significant implications for the further promotion and application of CO₂ and chemical agent flooding technology in analogous reservoirs.