Seepage Law of Nearly Flat Coal Seam Based on Three-Dimensional Structure of Borehole and the Deep Soft Rock Roadway Intersection

Lei Zhang, Chen Jing, Shugang Li, Ruoyu Bao and Tianjun Zhang
Additional contact information
Lei Zhang: College of Energy Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Chen Jing: Shaanxi Shanmei Huangling Mining Group Co., Ltd., Yan’an 727307, China
Shugang Li: College of Safety Science and Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Ruoyu Bao: Information Research Institute of the Ministry of Emergency Management, Beijing 100029, China
Tianjun Zhang: College of Safety Science and Engineering, Xi’an University of Science and Technology, Xi’an 710054, China

Energies, 2022, vol. 15, issue 14, 1-14

Abstract: Exploring the evolution characteristics of gas seepage between boreholes during the drainage process is critical for the borehole’s layout and high-efficiency gas drainage. Based on the dual-porous medium assumption and considering the effect of stress redistribution on coal seam gas seepage characteristics, a coal seam gas seepage model with a three-dimensional roadway and borehole crossing structure has been established and numerically calculated, concluding that the coal seam is between the drainage boreholes. The temporal and spatial evolution characteristics of gas pressure and permeability help elucidate the gas seepage law of the nearly flat coal seam associated with the deep soft rock roadway and borehole intersection model. The results indicate that: (1) The roadway excavation results in localized stress in some areas of the surrounding rock, reducing the strength of the coal body, increasing the expansion stress, and increasing the adsorption of gas by the coal body. (2) Along the direction of the coal seam, the permeability decreases initially and then increases. The gas pressure in the coal seam area in the middle of the borehole is higher than the pressure in the coal seam around the borehole, and the expansion stress and deformation increase, reducing the permeability of the coal body; when near the next borehole, the greater the negative pressure, the faster the desorption of the gas attracts the matrix shrinkage effect and causes the coal seam permeability rate to keep increasing. (3) The improvement of gas drainage with the overlapping arrangement of two boreholes firstly increases and then decreases as time goes on. (4) When the field test results and numerical simulation of the effective area of gas extraction are compared, the effectiveness of the model is verified. Taking the change of the porosity and the permeability into the model, it is able to calculate the radius of gas drainage more accurately.

Keywords: borehole roadway intersecting; gas drainage; effective stress; coupling calculation; gas seepage (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: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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