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<p>Understanding the influence of coal pore structure on methane adsorption is essential for efficient coalbed methane (CBM) development. This study investigates the multi-scale pore structure of deep coal from the Daning-Jixian block in the southeastern Ordos Basin and examines its effect on methane adsorption capacity (MAC). A combination of field emission scanning electron microscopy (FE-SEM), mercury intrusion porosimetry (MIP), low-pressure nitrogen adsorption (LPGA-N₂), and low-pressure carbon dioxide adsorption (LPGA-CO₂) was employed. A novel method for quantitatively characterizing MAC is proposed, considering both the interaction potential between methane molecules and pore walls and the close-packed molecular arrangement. The results show that: (1) The coal samples feature diverse pore types and complex structures, dominated by tissue and gas pores. Total pore volume ranges from 0.273 to 0.479&#xa0;cm³/g, with micropores contributing 25.05%–50.55%. Specific surface area (SSA) ranges from 246.12 to 281.64&#xa0;m²/g, with micropores accounting for 91.65%–96.85%. (2) MAC is high, with Langmuir volumes of 26.64–34.38&#xa0;cm³/g. The rough surfaces of tissue pores promote the formation of numerous smaller pores, enhancing adsorption. Moisture and ash content show a negative correlation with Langmuir volume. (3) Based on the quantitative characterization results of multi-scale pore structure, MAC calculated using the new method falls within the range of 24.73 to 33.95&#xa0;cm³/g. The calculated results exhibit good consistency with the measured Langmuir volume, with an absolute error ranging from 3.82% to 13.76%. The research results are of great significance for understanding the methane adsorption mechanism in coal.</p>

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Multi-scale pore structure characterization of deep coals and its impact on methane adsorption capacity in Daning-Jixian block, Southeastern Ordos basin

  • 期刊论文

  • 发表日期：

    2025年11月12日

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  • Cheng Meng,
  • Xiangyu Fan,
  • Cen Chen,
  • Chengwang Wang,
  • Bobo Li,
  • Qiangui Zhang

摘要

Understanding the influence of coal pore structure on methane adsorption is essential for efficient coalbed methane (CBM) development. This study investigates the multi-scale pore structure of deep coal from the Daning-Jixian block in the southeastern Ordos Basin and examines its effect on methane adsorption capacity (MAC). A combination of field emission scanning electron microscopy (FE-SEM), mercury intrusion porosimetry (MIP), low-pressure nitrogen adsorption (LPGA-N₂), and low-pressure carbon dioxide adsorption (LPGA-CO₂) was employed. A novel method for quantitatively characterizing MAC is proposed, considering both the interaction potential between methane molecules and pore walls and the close-packed molecular arrangement. The results show that: (1) The coal samples feature diverse pore types and complex structures, dominated by tissue and gas pores. Total pore volume ranges from 0.273 to 0.479 cm³/g, with micropores contributing 25.05%–50.55%. Specific surface area (SSA) ranges from 246.12 to 281.64 m²/g, with micropores accounting for 91.65%–96.85%. (2) MAC is high, with Langmuir volumes of 26.64–34.38 cm³/g. The rough surfaces of tissue pores promote the formation of numerous smaller pores, enhancing adsorption. Moisture and ash content show a negative correlation with Langmuir volume. (3) Based on the quantitative characterization results of multi-scale pore structure, MAC calculated using the new method falls within the range of 24.73 to 33.95 cm³/g. The calculated results exhibit good consistency with the measured Langmuir volume, with an absolute error ranging from 3.82% to 13.76%. The research results are of great significance for understanding the methane adsorption mechanism in coal.