Sensitivity simulation and analysis of CO2 injection for enhanced coalbed methane recovery

Injecting CO
₂
into a coal seam with the purpose of enhancing desorption of coalbed methane can be applied to the long-term storage of CO
₂
, which accompanies with complex coal gas interactions. In this study, a fully coupled coal deformation, gas flow, CH
₄
-CO
₂
counter-diffusion and gas absorption/desorption finite element (FE) model was developed to investigate sensitivity of CO
₂
injection related parameters. Modeling results indicate that (1) CO
₂
injectivity is positively sensitive to injecting pressure, so trying to increase the injecting pressure within the safe pressure threshold of coal seam, is an efficient solution to improve the methane recovery efficiency; (2) Initial coal permeability has positive impact on the performance of CO
₂
replacing methane. Larger initial permeability accompanies with larger CO
₂
injectivity; (3) Increase to coal elastic modulus results in lower coal permeability and CO
₂
injectivity, showing that lower coal mechanical properties could be more suitable to binary gas diffusion.