Research on coalbed methane microscopic seepage characteristics of medium and high-rank coal

ABSTRACT

In the present study, the microscopic seepage characteristics of coalbed methane (CBM) in medium and high-rank coal are investigated. Moreover, the influence of the coal pore structure on the CBM migration is studied. To this end, X-ray μCT scanning technology is utilized to construct the microscopic pore structure model of medium and high-rank coal. Then, the established model is transformed into a vectorized CAD solid model. Numerical simulation under different working conditions is carried out. The obtained results show that the pore system of coal is in a connected state. However, not all pores can penetrate the entire seepage direction. It is found that pore connectivity is the most important factor determining the CBM seepage performance. As coal metamorphism increases, the corresponding seepage pore connectivity decreases, pore throat radius decreases, seepage channels in coal seams decrease and the coal permeability decreases. Meanwhile, permeability anisotropy and the pore pressure of the coal have different changing laws along different seepage paths. It should be indicated that there is a dominant seepage direction. As the degree of coal metamorphism increases, the permeability in all directions gradually decreases.

KEYWORDS:

• Micro-CT technology
• medium and high-rank coal
• coalbed methane
• microscopic seepage
• permeability

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was financially supported by National key research and development Project [2018YFB0605601], Science and Technology Innovation and Entrepreneurship Fund Special Project of Tiandi Technology Co., Ltd. [2020-TD-MS003, 2019-TD-QN023], National Natural Science Foundation of China [51874178], Science and Technology Development Fund of Coal Science and Technology Research Institute [2018CX05].

Notes on contributors

Yongpeng Fan

Dr. Yongpeng Fan  graduated from Liaoning Technical University in 2019. He is currently working at the Coal Science Research Institute and is engaged in research on mine gas prevention and control. Zhonggang Huo graduated from Liaoning Technical University in 2006. He is currently working at the Coal Science Research Institute and is engaged in mine ventilation and safety research.

Longyong Shu

Longyong Shu graduated from China University of Mining and Technology in 2019. He is currently working at the Coal Science Research Institute and is engaged in research on mine gas prevention and control.

Zhonggang Huo

Zhonggang Huo graduated from Liaoning Technical University in 2006. He is currently working at the Coal Science Research Institute and is engaged in mine ventilation and safety research.

Jinwei Hao

Dr.Jinwei Hao graduated from the Coal Science Research Institute in 2019 and is currently engaged in research on mine gas prevention and control.

Yang Li

Yang Li graduated from Henan University of Technology in 2019. He is currently working at the Coal Science Research Institute and is engaged in research on mine gas prevention and control.

Xiaoyang Guo

Dr. Xiaoyang Guo graduated from Liaoning Technical University in 2020. He is currently working at Taiyuan University of Technology and is engaged in research on the microstructure of coal bodies.