The production and gas channeling characteristics of CO2 flooding in ultra-low-permeability reservoirs was examined in detail through laboratory experiments under formation pressure and temperature. The factors influencing injection pressure and reservoir heterogeneity with CO2 channeling characteristics were also systematically studied. The results showed that the
CO2 flooding process in ultra-low-permeability reservoirs can be divided into three stages: (1) a gas-free stage, (2) a gas breakthrough stage and (3) a gas channeling stage. Among them, the oil recovery of the gas breakthrough stage contributed greatly to the total recovery, which is the key stage for improving oil recovery in ultra-low-permeability layers. The injection pressure of CO2 and the reservoir heterogeneity can affect the development of the gas-free stage, gas breakthrough stage and gas channeling stage to different degrees. Thus, maintaining the formation pressure, improving the heterogeneity of the reservoir and inhibiting the gas channeling to prolong the gas breakthrough stage during CO2 flooding are effective ways to improve the development efficiency of CO2 flooding in ultra-low-permeability layers.