A fully coupled fluid flow and geomechanics model is proposed for ECBM and CO2 underground storage with consideration of multi⁃component multi⁃process transportation in porous media to investigate the complicated geomechanical effects, and the corresponding numerical solver is developed. The effect of geomechanical effects and injection gas components on permeability and injection/production index were also investigated. The results indicate that both effective stress effect and matrix swelling/shrinkage can significantly affect porosity and permeability, but in opposite direction. Matrix swelling induced by CO2 injection can lead to about 90% loss in permeability around injector. The increasing of Young's modulus or decreasing of matrix Langmuir strain, will induce earlier CO2 breakthrough time and lower coalbed methane recovery and CO2 sequestration amount. These results can provide better methane production prediction and support high⁃efficient productivity improvement.