Abstract: In order to improve the recovery efficiency of air-foam injection flooding in fractured reservoirs, experiments of early-stage water flooding, air-foam flooding and subsequent water flooding were conducted in Chang6 Member reservoirs in the west-central area of Wangyao Block to optimize gas-liquid volume ratio, foam slug volume, injection pressure, injection rate and injection time. The results showed that, after the foam was injected into the core, the water content was decreased rapidly, the recovery percent was increased rapidly, the fractured core was plugged faster than the matrix core, but the plugging effect was poor; the earlier the air and foam were injected, the higher the final recovery efficiency; the optimal gas-liquid volume ratio, foam slug volume, injection pressure and injection rate were negatively correlated with the core permeability, and the permeability change was less sensitive to the optimal injection parameters due to high fracture permeability. The results of the study provide an important theoretical basis for fine injection of air-foam flooding in low-permeability fractured reservoirs.

Key words: air-foam flooding, injection parameters, optimization, fractured reservoir, experiment