Experimental Study on CO 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 CO 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 CO 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 CO 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, CO 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 CO foam flooding techniques.