Abstract: As the sweeping characteristics of CO₂ miscible flooding with injection-production coupling are not clearly understood and the gas channeling stage cannot be quantitatively identified, numerical simulation was applied to analyze the sweeping characteristics of CO₂ miscible flooding with injection-production coupling and determine the characterization indicators and classification standard of the gas channeling degree. The results showed that, compared with CO₂ continuous gas flooding, the development with injection-production coupling expanded the sweeping range of the gas flooding, delayed the time of gas channeling and improved the final recovery percent of the reservoir through pressurization, energy storage, pressure release and energy release; the results of gas channeling stages calculated by the new method were consistent with the field monitoring data, which can be used as the basis for the identification of the gas channeling stage in the mine; the greater the reservoir porosity, the longer the gas-free oil production stage and the later the gas channeling development stage; the closer the production well was to the gas injection well, the earlier the gas breakthrough time was, and the duration of complete gas channeling was 3 148 d, 4 120 d and 5 610 d for the inverse nine-spot pattern, row pattern and five-spot pattern, respectively. The research results can provide theoretical guidance for the enhanced oil recovery of low permeability reservoirs under development by CO₂ miscible flooding with injection-production coupling.

Key words: low-permeability reservoir, CO₂ miscible flooding, injection-production coupling, gas channeling stage, sweep characteristics, quantitative characterization