Numerical simulation of CO₂-ECBM based on coal sample scale

In order to achieve the ECBM experimental research and numerical simulation combined analysis, based on the permeability model under the laboratory stress conditions, a numerical model of CO₂-ECBM, including the pore and fracture medium system of coal, was established.Numerical simulation of CO₂-ECBM at different CO₂ injection pressures was carried out.The results show that the greater the injection pressure of CO₂, the less time it takes for CO₂ to flow out from the end of the coal after injection.The injection of CO₂ will cause the permeability of coal to decrease, and when the injection pressure is small, the change of permeability will be divided into three stages, including the stage of effective stress, the stage of constant CH₄ pressure, and the stage of CO₂ adsorption.When the injection pressure is large, there is no stage of the stage of constant CH₄ pressure.As the injection pressure increases, the CH₄ output increases greatly after a certain period of time after the injection of CO₂, and then the CH₄ output is smaller at the later stage of gas injection.The above results are instructive for the CO₂-ECBM experiments and the analysis of its experimental results.