Injecting  CO₂ into the subsurface oil and gas reservoirs and coalbeds, at the moment, is the most realistic choice in reducing the  CO₂  emission into the atmosphere, which can not only enhance the recoveries of the oil and gas, and coal bed methane, but also can sequestrate partial CO₂ within the subsurface reservoirs and coal beds permanently.  CO₂  enhanced oil recovery ( CO₂ -EOR) is generally performed in the late stage of oil exploration and development, by which  CO₂  is injected into the oil reservoirs to enhance the oil recoveries, in general, up to 10-15% by volume. Similarly,  CO₂  enhanced gas recovery ( CO₂ -EGR) is to inject the  CO₂  into the gas reservoirs to enhance the gas recoveries. The extracted gas reservoirs can provide voluminous pore spaces for CO₂  storage prior to flooding by formation waters. In this case, Injecting  CO₂  into the subsurface gas reservoirs would increase the reservoir pressure and maintain the primary formation pressure, which can keep the integrity and reduce the damage of reservoirs. In the meantime, the traps of oil and gas pools are also good compartments from which leakage of injected  CO₂  is prevented, such that the  CO₂  is sequestrate in the subsurface permanently. In addition, the  CO₂  can also be used to enhance the recovery of coalbed methane by injecting  CO₂  into the coalbeds ( CO₂ -ECBM), due to the differences in coal adsorption for  CO₂  and CH₄. Higher absorption of  CO₂  related to CH₄ by coals would result in the displacement of CH₄ by  CO₂  in place, thereby enhancing the recovery of coalbed methane when the  CO₂  is injected into the CH₄-bearing coalbeds.