Numerical simulation of enhancing coalbed methane recovery by injecting CO2 with heat injection

The technology used to enhance coalbed methane(CBM) recovery by injecting CO(CO-ECBM) with heat, combining heat injection with COinjection, is still in its infancy; therefore, theoretical studies of this CO-ECBM technology should be perused. First, the coupling equations of the di usion–adsorption–seepage–heat transfer fields of gas are established. The displacement processes under di erent pressures and temperatures are simulated by COMSOL. Finally, the displacement effects, a comparison of the COstorage capacity with the CHoutput and the e ective influencing radius of COinjection are analyzed and discussed. The results show that(1) the displacement pressure and temperature are two key factors influencing the CHoutput and the COstorage capacity, and the increase in the COstorage capacity is more sensitive to temperature and pressure than the CHoutput.(2) The gas flow direction is from the injection hole to the discharge hole during the displacement process, and the regions with high velocity are concentrated at the injection hole and the discharge hole.(3) A reduction in the CHconcentration and an increase in the COconcentration are obvious during the displacement process.(4) The e ective influencing radius of injecting COwith heat increases with the increase in time and pressure. The relationship between the e ective influencing radius and the injection time of COhas a power exponential function, and there is a linear relationship between the functional coe cient and the injection pressure of CO. This numerical simulation study on enhancing CBM recovery by injecting COwith heat can further promote the implementation of CO-ECBM project in deep coal seams.