Abstract:
In order to explore the role of Klinkenberg effect and Klinkenberg factor in different states in the process of CO
2-Enhanced Coal Bed Methane (CO
2-ECBM), the effects of Klinkenberg factor of zero, fixed Klinkenberg factor and dynamic Klinkenberg factor on CO
2-ECBM were simulated and analyzed by COMSOL finite element software. The dynamic changes of CH
4 and CO
2 pressure with this factor were studied, and the CH
4 gas production was compared with the engineering practice. The results show that the effective permeability of CH
4 and CO
2 increases slowly at first, then decreases rapidly and gradually tends to be gentle. Compared with the fixed Klinkenberg factor or Klinkenberg factor of zero, the effective permeability of CH
4 and CO
2 under the influence of dynamic Klinkenberg factor is larger. When the Klinkenberg factor is a dynamic variable, the effective permeability of CO
2 is less than that of CH
4 due to the influence of molar mass and dynamic viscosity of different gases. The CH
4 pressure in the coal seam decreases faster and the CO
2 pressure rises faster. When the Klinkenberg factor is fixed or zero, the CH
4 pressure in the coal seam will be overestimated, and the influence range of CH
4 extraction and CO
2 pressure injection will be underestimated, and the valuation will increase with time. The research results are helpful to analyze the variation trend of effective permeability of CH
4 and CO
2, estimate the influence range of CH
4 extraction and CO
2 injection and the gas production of CH
4, and have theoretical guiding significance in exploring coal seam permeability, optimizing well pattern layout and quantitatively evaluating gas production of coalfield.