In this work, using fractured shale cores, isothermal adsorption experiments and core flooding tests were conducted to investigate the performance of injecting different gases to enhance shale gas recovery and CO₂ geological storage efficiency under real reservoir conditions. The adsorption process of shale to different gases was in agreement with the extended-Langmuir model, and the adsorption capacity of CO₂ was the largest, followed by CH_4, and that of N₂ was the smallest of the three pure gases. In addition, when the CO₂ concentration in the mixed gas exceeded 50%, the adsorption capacity of the mixed gas was greater than that of CH₄, and had a strong competitive adsorption effect. For the core flooding tests, pure gas injection showed that the breakthrough time of CO₂ was longer than that of N₂, and the CH₄ recovery factor at the breakthrough time (R_{\mathrm{C}{\mathrm{H}}_4}) was also higher than that of N₂. The R_{\mathrm{C}{\mathrm{H}}_4} of CO₂ gas injection was approximately 44.09%, while the R_{\mathrm{C}{\mathrm{H}}_4} of N₂ was only 31.63%. For CO₂/N₂ mixed gas injection, with the increase of CO₂ concentration, the R_{\mathrm{C}{\mathrm{H}}_4} increased, and the R_{\mathrm{C}{\mathrm{H}}_4} for mixed gas CO₂/N₂ = 8:2 was close to that of pure CO₂, about 40.24%. Moreover, the breakthrough time of N₂ in mixed gas was not much different from that when pure N₂ was injected, while the breakthrough time of CO₂ was prolonged, which indicated that with the increase of N₂ concentration in the mixed gas, the breakthrough time of CO₂ could be extended. Furthermore, an abnormal surge of N₂ concentration in the produced gas was observed after N₂ breakthrough. In regards to CO₂ storage efficiency (S_{\mathrm{s}\mathrm{t}\mathrm{o}\mathrm{r}\mathrm{a}\mathrm{g}\mathrm{e}\text{-}{\mathrm{C}\mathrm{O}}_2}), as the CO₂ concentration increased, S_{\mathrm{s}\mathrm{t}\mathrm{o}\mathrm{r}\mathrm{a}\mathrm{g}\mathrm{e}\text{-}{\mathrm{C}\mathrm{O}}_2} also increased. The S_{\mathrm{s}\mathrm{t}\mathrm{o}\mathrm{r}\mathrm{a}\mathrm{g}\mathrm{e}\text{-}{\mathrm{C}\mathrm{O}}_2} of the pure CO₂ gas injection was about 35.96%, while for mixed gas CO₂/N₂ = 8:2, S_{\mathrm{s}\mathrm{t}\mathrm{o}\mathrm{r}\mathrm{a}\mathrm{g}\mathrm{e}\text{-}{\mathrm{C}\mathrm{O}}_2} was about 32.28%.