The proved reserves of natural gas in place in China is huge. However

realizing the long-term large scale stable production of natural gas faces a series of challenges such as enhanced gas recovery（EGR） of complex gas reservoirs

especially for those unconventional resources such as shale gas

coalbed methane and tight sand gas. Under the background of carbon neutralization

CCUS-EGR technology has broad application prospects due to owing the functions of increasing gas rate and carbon reduction. The main EGR mechanisms for CO

2

flooding are summarized into three types: s

ubstitution due to dominant adsorption of carbon dioxide

continuous convective displacement and gas reservoir energy supplement. Under the consideration that the classification of occurrence states of the adsorbed

free and dissolved natural gas are applicable to all types of the gas reservoirs. The prediction method of increased natural gas ultimate recovery factor by CO

2

flooding is further deduced. It is found that CO

2

flooding is expected to improve shale gas recovery of more than 20 percentage points by this method. In order to break through the technology of greatly improving natural gas recovery

it is suggested to evaluate the potential of CO

2

flooding to improve natural gas recovery for gas reservoirs with good geological sequestration conditions

assess the economic feasibility of CCUS-EGR technology applying in target gas reservoirs

and carry out major pilot tests of CO

2

flooding in various types of gas reservoirs. The synergistic displacement effect of flue gas components and the technology of expanding CO

2

sweeping volume should be focused especially.