Characteristics of Stress-Displacement-Fracture Multi-Field Evolution around Gas Extraction Borehole

Xiaoyan Sun, Qican Ran (), Hao Liu (), Yanhao Ning and Tengfei Ma
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Xiaoyan Sun: School of Energy and Mining Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China
Qican Ran: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Hao Liu: College of Aerospace Engineering, Chongqing University, Chongqing 400044, China
Yanhao Ning: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
Tengfei Ma: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China

Energies, 2023, vol. 16, issue 6, 1-21

Abstract: To ensure the effectiveness of the gas extraction borehole, it is necessary to investigate the stress-displacement-fracture evolution of the coal around the borehole. In this study, by constructing a numerical model of a gas extraction borehole, the burial depth and side pressure coefficient are used to characterize the overall stress level of the borehole and the difference in stress distribution caused by complex stress conditions. First, the stress time-varying pattern and force chain distribution of coal around the borehole were revealed. Then, the displacement time-varying pattern and displacement distribution of coal around the borehole were elucidated. Then, the microfracture distribution of coal around the borehole, which characterizes the microfractures, was analyzed. Finally, the validity of the numerical results was verified. The results showed that, after the stress field of the coal around the borehole was adjusted, the force chain of the borehole was unevenly distributed and the stress concentration phenomenon appeared. With the increase in burial depth, the stress around the borehole gradually increased, while the range of stress concentration zone in the borehole kept increasing, and the borehole changed from unilateral instability to bilateral instability. Moreover, the displacement field around the borehole was distributed in the shape of a ”disk leaf”. With the increase in burial depth, the deformation of coal around the borehole increased. With the increase in the side pressure coefficient, the vertical and horizontal displacement also increased gradually. Furthermore, there was a certain correspondence between the development of fracture and the deformation around the coal. With the increase in burial depth, the development of fractures was gradually obvious, and the distribution characteristics were concentrated in the middle and dispersed around. This study provides a theoretical reference for the stability of gas extraction boreholes, aiming to improve the gas extraction effect.

Keywords: gas extraction borehole; multi-field evolution; numerical simulation; burial depth; side pressure coefficient (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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