Abstract: Nowadays, with the increase of CO₂ emissions, the global greenhouse effect has become increasingly significant, so the disposal of CO₂ become more and more important. While in China all of the projects of CO₂ storage are conducted in oil reservoir or saline formation, there is no project of CO₂ flooding plus CO₂ capture and storage （CCS）in gas reservoirs and little studies about it. By reviewing a large number of studies about this topic, and the existing projects of CO₂ flooding and geological storage projects of depleted gas reservoirs, as well as CO₂ flooding simulation studies, this paper analyzed the affecting factors, the advantages and disadvantages of enhanced gas recovery （EGR）by CO₂ flooding in gas reservoirs, and pointed out that the works should be done when applying it to tight gas reservoirs. The result shows that CO₂ storage in depleted gas reservoirs is reliable, with large storage capacity and low cost, and has some additional economic benefits. Irreducible water can reduce the impact of heterogeneity on EGR. Comparing with the results of gaseous CO₂ flooding in moderate or high permeability gas reservoirs, the effect of liquid or supercritical CO₂ flooding is better. Moreover, the later the start time of CO₂ flooding is or the higher the injection pressure and rate is, the higher the gas recovery factor will be.

Key words: produced liquid, surfactant/polymer compound flooding, reinjection way, oil displacement