Analysis on gas emission characteristics and permeability inversion of hydraulic slotting borehole

doi:10.16265/j.cnki.issn 1003-3033.2021.07.015

Abstract

Abstract: In order to study influence of hydraulic slotting on borehole gas drainage, underground field test was designed based on theoretical analysis of borehole gas seepage and slotting increasing permeability mechanism, meanwhile,gas emission velocity, cumulative emission and variation characteristics of gas pressure around slotting borehole were investigated. According to gas emission velocity inversion, change process of coal permeability and its influencing factors were discussed and analyzed. The results show that gas emission rate of slotted borehole generally presents four stages of rapid attenuation, including slow attenuation, small amplitude increase and then attenuation, and large amplitude increase, which are related to the stress evolution around slotting, coal mechanical behavior, coal seam pressure water and other factors. After about 40 days of slotting operation, gas emission rate of borehole begin to increase significantly, and gas pressures around slotted borehole decrease. In general, decline rate decreases far away from slotted borehole. Permeability of slotted coal mass shows changing trend that first decreases, then increases slightly, and then increases greatly. Permeability has a negative correlation with gas pressure of surrounding coal seam. Inversion analysis results are consistent with existing simulation conclusions.

Key words: hydraulic slotting, gas emission from borehole, coal permeability, gas drainage, slotting increasing permeability

CLC Number:

X936

HAN Lei, SHEN Chunming, WANG Weihua. Analysis on gas emission characteristics and permeability inversion of hydraulic slotting borehole[J]. China Safety Science Journal, 2021, 31(7): 105-112.

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