Abstract: To address the difficulty of optimizing the injection parameters of different permeability reservoirs in the process of air foam flooding in low-permeability heterogeneous reservoir, in a case study of natural core from Change₆³ Formation in Ansai Oilfield, experiments on injection parameter optimization for air foam flooding were performed with one-dimensional core flow experimental equipment to optimize the gas-liquid ratio, foam slug volume, injection pressure, injection rate and injection time to obtain the best injection parameters, and analyze the optimization law of injection parameters for air foam flooding in different permeability reservoirs. The results showed that with the increase of gas-liquid ratio, foam slug volume, injection pressure and injection rate, the recovery percent of the same group of cores increased, and when the injection parameters reached a certain level, the recovery percent increment increased or decreased and there was an optimal value for each injection parameter; different injection parameters greatly affected the recovery percent, especially sensitive to the reservoirs with low permeability; there was a good exponential decreasing relationship between the permeability and the optimal injection gas-liquid ratio, injection volume, injection pressure and injection rate, and air foam injection at low water cut resulted in a recovery efficiency. The study results provide a theoretical basis for regional layered and fine injection of air foam flooding in low-permeability reservoir.

Key words: air foam flooding, enhanced recovery efficiency, injection parameter optimization, low-permeability reservoir, optimization design, experimental study, Ansai Oilfield