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ORIGINAL RESEARCH article

Front. Earth Sci.
Sec. Economic Geology
Volume 12 - 2024 | doi: 10.3389/feart.2024.1413069
This article is part of the Research Topic Efficient Exploration and Development of Unconventional Natural Gas View all 4 articles

Nanoscale Pore Structure in Anthracite Coals and Its Effect on Methane Adsorption Capacity

Provisionally accepted
Qiang Xu Qiang Xu 1Zebin Wang Zebin Wang 2Ruyue Wang Ruyue Wang 3Yue Zhao Yue Zhao 1Quanyun Miao Quanyun Miao 1Zhengguang Zhang Zhengguang Zhang 1*Xiujia Bai Xiujia Bai 1Feng Xinxin Feng Xinxin 4
  • 1 China National Administration of Coal Geology (CNACG), Beijing, China
  • 2 PetroChina Coalbed Methane Company Limited, Beijing, China
  • 3 SINOPEC Petroleum Exploration and Production Research Institute, Beijing, Beijing, China
  • 4 Shaanxi Tiancheng Petroleum Technology Co. Ltd., Xian, Shaanxi Province, China

The final, formatted version of the article will be published soon.

    Although significant amounts of methane are present in anthracite coal seams, coalbed methane resources cannot be extracted effectively and quickly. This study mainly focused on investigating the pore system and methane adsorption capacity to clarify the storage of coalbed methane. Anthracite coal samples from the Anzenan coalbed methane block in China were collected and pore characterization methods (low-pressure N2 adsorption, mercury injection experiments, and scanning electron microscopy observations) and methane isothermal adsorption experiments were conducted. The results showed that few mesopores and nanoscale macropores were present in the anthracite coal samples. The volume of the 2-300 nm pores in these coal samples obtained from the N2 adsorption experiment was lower than 0.01 cm 3 /g. Scanning electron microscopy (SEM) observations also revealed that only a small number of mesopores and nanoscale macropores could be seen, and most of these pores were isolated. In terms of the methane isothermal adsorption data, it was found these anthracite coals have large methane adsorption capacity, and the Langmuir volume ranges from 19.5 to 28.4 cm 3 /g, with an average of 22.2 cm 3 /g. With increasing ash yield, the Langmuir volume decreased linearly, meaning that methane molecules were mainly adsorbed in the organic matter of coal. As methane is mainly adsorbed in the micropores of coal organic matter and there are few mesopores and nanoscale macropores in the organic pores in coal, there are not enough tunnels to transport the adsorbed methane molecules to the outside. Thus, it is difficult to extract coalbed methane from anthracite.

    Keywords: Anthracite coal, Coalbed methane, Pore system, Methane adsorption capacity, Ash yield

    Received: 06 Apr 2024; Accepted: 29 Jul 2024.

    Copyright: © 2024 Xu, Wang, Wang, Zhao, Miao, Zhang, Bai and Xinxin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Zhengguang Zhang, China National Administration of Coal Geology (CNACG), Beijing, China

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