Experimental Study on CO₂ Foam Flooding System in High Temperature and Low-Permeability Reservoirs

In response to the critical challenges posed by high temperatures (97.3 °C), difficulties in water injection, gas channeling during CO₂ injection production, and the pressing need to transform the development approach for significantly enhancing oil recovery in the low-permeability H79 block of the Jilin Oilfield, a novel sulfonate-type alkyl alcohol zwitterionic surfactant, FA278, has been identified. This surfactant exhibits a foaming volume of 920 mL and a liquid drainage half-life of 195 s. A CO₂ foam flooding system comprising 0.40% FA278 and 0.12% FS24 has been developed specifically to address the conditions prevalent in high-temperature and low-permeability reservoirs. The system demonstrates a foaming volume of 740 mL, with a liquid drainage half-life of 1335 s; it also achieves a surface tension of 25.99 mN/m and an interfacial tension of 1.00 mN/m. Notably, it exhibits an excellent oil resistance and stability. Results from natural outcrop core displacement experiments indicate that this newly developed CO₂ foam flooding system can enhance recovery by an impressive margin of 11.09%, building upon an initial total recovery rate of 76.05% achieved through water flooding, CO₂ flooding, and water-alternating gas (WAG) flooding methods; ultimately leading to a final oil recovery reaching up to 87.14%. The efficacy of this oil displacement method is remarkable, providing essential technical support for significantly enhanced oil recovery in high-temperature and low-permeability reservoirs via CO₂ foam flooding techniques.