ABSTRACT:

CO2 finger-channeling seriously affects oil displacement efficiency. It is necessary to research the factors that influence finger-channeling and prevention of finger-channeling in CO2 flooding. In this paper 1) the effects of different gas injection factors on finger-channeling degree in CO2 gas flooding and oil displacement efficiency by slim tube and core displacement experiments are studied, 2) oil-gas interfacial characterization under high temperature and high pressure is analyzed by interface tensiometer, and 3) the inhibitory effect of different gas injection patterns on channeling in heterogeneous reservoirs is compared by heterogeneous core displacement experiments. The results show the finger-channeling degree of CO2 gas drive is lower than that of natural gas flooding oil and has higher displacement efficiency under the same injection pressure. With gas injection pressure increasing, the finger-channeling degree in both CO2 gas drive and natural gas drive decreases while the oil displacement efficiency significantly increases. Oil displacement efficiency influenced by oil/gas ratio, MMP and pressure. According to oil-gas interfacial tension test, with pressure increasing, the extraction effect of injection gas on crude oil is enhanced, the oil-gas interfacial tension decreases, oil and gas properties are closer, which is conducive to suppress finger-channeling. Meanwhile, alternate injection of water and gas is one of the most effective ways to restrain gas drive in heterogeneous reservoirs.

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