Abstract:

After  oil recovery in Gudao Oil Field by water flooding, polymer flooding and subsequent water flooding, the remaining  underground oil is highly decentralized, the watercut of the producing fluid is higher, and the producing process becomes more difficult. How to enhance oil recovery of the subsequent water flooding reservoir is especially important, which can improve the overall development performance of the oil field. With the principle of profile control and oil drive,  indoor research on enhancing recovery about airfoam flooding was put forth. A lab test simulated the geological model of a positive rhythmic reservoir at high water cut stage,which was composed of  high／middle／low permeability parallel core. By determining the resistance factor with different mass fractions of blowing agent and different gas／liquid ratios, the best optimized results were obtained. The best mass fraction of blowing agent was 0.5％, and the best underground gas／liquid volume ratio was 1∶1. Indoor laboratory investigation was  carried out concerning seal, profile and oil displacement characteristics under the conditions of low and high ratios of total oil produced to the original oil in place. The results showed that on the condition of low recovery percent after water drive (15.37％), and the enhanced oil recovery (EOR) increased 22.02％ by air foam flooding. After the first round air foam flooding and succeeding water flooding, the EOR was  increased 9.35％ by the second air foam flooding with pure air slug, and with a  recovery percent of 45.53％.

Key words:  air foam, resistance factor, heterogeneity, high water-cut, recovery ratio