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<p>With the continued decline in shallow coal reserves, exploiting deeper coal is now increasingly important for maintaining stable energy supply. China’s deep coal seams contain substantial coalbed methane (CBM) resources, yet the accompanying high geothermal temperatures and strong in-situ stresses markedly reduce gas drainage efficiency. Methane desorption and diffusion in coal, which govern gas migration, are highly sensitive to variations in temperature and pressure. In deep reservoirs, these two processes interact and form a coupled system that modifies methane-release behavior. To investigate this coupled response, this study performed orthogonally-designed desorption experiments under combined temperature–pressure conditions and evaluated the corresponding changes in desorption performance and diffusion coefficients. On this basis, a temperature-dependent correction model for the diffusion coefficient is established. The results demonstrated that increasing temperature decreases the total desorbed amount while accelerating the early desorption rate, whereas higher pressure enhances overall desorption capacity and alleviates temperature-induced inhibition. Compared with raw coal, tectonic coal responds more noticeably to pressure and may display an offsetting interaction between temperature and pressure under specific conditions. Temperature exerts the dominant influence on diffusion-coefficient evolution, and pressure plays a secondary role. These findings clarify the mechanism by which temperature–pressure coupling governs methane release and transport in coal, offering a theoretical basis for enhancing CBM recovery from deep coal seams.</p>

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Desorption–Diffusion Characteristics of Gas in Coal Under Coupled Temperature–Pressure Conditions: Their Antagonistic Effects and Impacts on Gas Transport in Deep Coal Seams

  • 期刊论文

  • 发表日期：

    2026年7月24日

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  • Wei Zhao,
  • Haichao Li,
  • Kai Wang,
  • Jiaxun Huang,
  • Bo Li,
  • Lihui Wang,
  • Haozhen Zhou,
  • Yidu Hong

摘要

With the continued decline in shallow coal reserves, exploiting deeper coal is now increasingly important for maintaining stable energy supply. China’s deep coal seams contain substantial coalbed methane (CBM) resources, yet the accompanying high geothermal temperatures and strong in-situ stresses markedly reduce gas drainage efficiency. Methane desorption and diffusion in coal, which govern gas migration, are highly sensitive to variations in temperature and pressure. In deep reservoirs, these two processes interact and form a coupled system that modifies methane-release behavior. To investigate this coupled response, this study performed orthogonally-designed desorption experiments under combined temperature–pressure conditions and evaluated the corresponding changes in desorption performance and diffusion coefficients. On this basis, a temperature-dependent correction model for the diffusion coefficient is established. The results demonstrated that increasing temperature decreases the total desorbed amount while accelerating the early desorption rate, whereas higher pressure enhances overall desorption capacity and alleviates temperature-induced inhibition. Compared with raw coal, tectonic coal responds more noticeably to pressure and may display an offsetting interaction between temperature and pressure under specific conditions. Temperature exerts the dominant influence on diffusion-coefficient evolution, and pressure plays a secondary role. These findings clarify the mechanism by which temperature–pressure coupling governs methane release and transport in coal, offering a theoretical basis for enhancing CBM recovery from deep coal seams.