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<p>Numerical simulation is an effective method to study the effect of CO<sub>2</sub>-enhanced coalbed methane recovery&#xa0;(CO<sub>2</sub>-ECBM), which can overcome the limitations of a small-scale research platform in the laboratory. Nevertheless, the current mathematical models of CO<sub>2</sub>-ECBM ignore the influence of CH<sub>4</sub>/CO<sub>2</sub> competitive adsorption, resulting in significant underestimation on CO<sub>2</sub>-ECBM&#xa0;effect. Therefore, we established a new model of CO<sub>2</sub>-ECBM emphasizing the competitive adsorption effect of methane (CH<sub>4</sub>) and carbon dioxide (CO<sub>2</sub>), and simulated the spatiotemporal evolution of CH<sub>4</sub> and CO<sub>2</sub> pressures in coalbed during the process. The results indicated that, compared with conventional extraction, CO<sub>2</sub>-ECBM can promote coalbed methane recovery greatly. After using CO<sub>2</sub>-ECBM, the CH<sub>4</sub> pressure in the pore and fracture of coal at 0.5&#xa0;m from the CO<sub>2</sub> injection borehole reduced by 63.79 and 64.91%, respectively, and those at 2.5&#xa0;m reduced by 70.27 and 68.06%, respectively. During the CO<sub>2</sub>-ECBM, within the range of 1.0&#xa0;m from the CO<sub>2</sub> injection borehole, the excessive competitive adsorption and displacement effects of CO<sub>2</sub> caused the special phenomenon of methane reverse diffusion, resulting in a temporary rebound of CH<sub>4</sub> pressure in pore. Besides, the CO<sub>2</sub>-ECBM&#xa0;effect increased distinctly with increasing CO<sub>2</sub> injection pressure. Extending the CO<sub>2</sub> injection time and reducing the borehole spacing also could increase CO<sub>2</sub>-ECBM effect distinctly. The results can provide valuable reference and theoretical direction for correctly evaluating the field application effect of CO<sub>2</sub>-ECBM and providing optimal technological parameters.</p>

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Influence of CH4/CO2 Competitive Adsorption on CO2-Enhanced Coalbed Methane Recovery

  • 期刊论文

  • 发表日期：

    2026年2月18日

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  • Purui Li,
  • Yongliang Yang,
  • Jinhu Li,
  • Guoqin Wang,
  • Yifan Zhang,
  • Kaiyang Gao

摘要

Numerical simulation is an effective method to study the effect of CO2-enhanced coalbed methane recovery (CO2-ECBM), which can overcome the limitations of a small-scale research platform in the laboratory. Nevertheless, the current mathematical models of CO2-ECBM ignore the influence of CH4/CO2 competitive adsorption, resulting in significant underestimation on CO2-ECBM effect. Therefore, we established a new model of CO2-ECBM emphasizing the competitive adsorption effect of methane (CH4) and carbon dioxide (CO2), and simulated the spatiotemporal evolution of CH4 and CO2 pressures in coalbed during the process. The results indicated that, compared with conventional extraction, CO2-ECBM can promote coalbed methane recovery greatly. After using CO2-ECBM, the CH4 pressure in the pore and fracture of coal at 0.5 m from the CO2 injection borehole reduced by 63.79 and 64.91%, respectively, and those at 2.5 m reduced by 70.27 and 68.06%, respectively. During the CO2-ECBM, within the range of 1.0 m from the CO2 injection borehole, the excessive competitive adsorption and displacement effects of CO2 caused the special phenomenon of methane reverse diffusion, resulting in a temporary rebound of CH4 pressure in pore. Besides, the CO2-ECBM effect increased distinctly with increasing CO2 injection pressure. Extending the CO2 injection time and reducing the borehole spacing also could increase CO2-ECBM effect distinctly. The results can provide valuable reference and theoretical direction for correctly evaluating the field application effect of CO2-ECBM and providing optimal technological parameters.