Abstract
Based on the dynamic expressions of permeability and porosity of the coal seam derived in the paper, a multiphysical field coupling numerical model of gas migration under the interaction of stress field and seepage field was established. The gas drainage project #3 Coal Seam operated by Sima Coal Industry Co., Ltd., was selected as the study object. Taking different drainage time periods in various positions of drainage holes into consideration, combined with the advance situation of the 1207 working face in the Sima Coal Mine, a mixed layout gas drainage scheme featured with the effective borehole spacing was obtained through the COMSOL multiphysics simulation. In addition, a series of field industrial tests were performed to validate the research result, revealing that comprehensively considering the extraction time of coal and optimizing the layout of extraction boreholes can effectively improve the engineering economic benefits.
Highlights
Coal seam gas drainage is one of the important measures to control mine gas [1, 2] a majority of researches take the effective drainage radius as the basis of drainage hole layout, overlooking the influences of the superimposed drainage and fracture expansion without taking the influence of different drainage times of drainage holes in different positions of the coal seam into account
Many existing studies fail to consider the establishment of a multiphysical field coupling model of gas migration under the interaction of the stress field and seepage field and overlook the dynamic nature of the permeability and porosity of the coal seam
Based on the changes of coal seam stress, gas pressure, and gas adsorption and desorption which tend to exert an important impact on the coal seam permeability and porosity, the dynamic expressions of coal seam permeability and porosity were deduced which was used to build the numerical model of a multiphysical field coupling for migration under the interaction of stress field and seepage field
Summary
Coal seam gas drainage is one of the important measures to control mine gas [1, 2] a majority of researches take the effective drainage radius as the basis of drainage hole layout, overlooking the influences of the superimposed drainage and fracture expansion without taking the influence of different drainage times of drainage holes in different positions of the coal seam into account. Many existing studies fail to consider the establishment of a multiphysical field coupling model of gas migration under the interaction of the stress field and seepage field and overlook the dynamic nature of the permeability and porosity of the coal seam. The gas drainage optimization of #3 Coal Seam in Sima Coal Industry Co., Ltd., of Lu’an Group was studied. Taking different drainage time periods in various positions of drainage holes into consideration, combined with the advance situation of the 1207 working face in the Sima Coal Mine, a mixed layout gas drainage scheme featured with the effective borehole spacing was obtained by the COMSOL multiphysics simulation. Geofluids industrial tests were performed for the purpose of validating the research
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