Experimental Investigation of the Effect of Groundwater on the Relative Permeability of Coal Bodies around Gas Extraction Boreholes

Mingkun Pang, Hongyu Pan (), Hang Zhang and Tianjun Zhang
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Mingkun Pang: College of Energy, Xi’an University of Science and Technology, Xi’an 710054, China
Hongyu Pan: College of Energy, Xi’an University of Science and Technology, Xi’an 710054, China
Hang Zhang: College of Safety Science and Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Tianjun Zhang: College of Safety Science and Engineering, Xi’an University of Science and Technology, Xi’an 710054, China

IJERPH, 2022, vol. 19, issue 20, 1-21

Abstract: Water infiltration in boreholes is a common problem in mine gas pre-extraction, where water infiltration can significantly reduce the efficiency of gas extraction and curtail the life cycle of the borehole. It is important to evaluate the effect of groundwater on the permeability of the coal body around a gas extraction borehole. In order to determine the seepage parameters of the fractured coal body system around the borehole, a water–gas two-phase seepage test was designed to determine the relative seepage parameters of the fractured coal media seepage system. The main conclusion is that the relative permeability of gas can be effectively increased by increasing the negative extraction pressure at the early stage of extraction to accelerate drainage to reduce the water saturation of the coal seam. Under the combined effect of porosity and seepage pressure, the relative permeability of gas and water in the fractured coal rock body shows three stages. The dependence of the total permeability on the effective stress is closely related to the stages in the evolution of the pore structure, and the total effective permeability decreases with the increase in the effective stress. A decrease in porosity can lead to a decrease in permeability and an increase in the non-Darcy factor. Through an in-depth analysis of the damage and permeability pattern of the coal body around the perimeter of the dipping borehole, the efficient and safe extraction of gas from dipping boreholes in water-rich mines is thus ensured.

Keywords: coal gas control; gas pre-extraction; gas extraction borehole; permeability of coal body; effect of groundwater (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (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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