Abstract
The influence of the ventilation system on the abandoned gob weakens, so the gas seepage characteristics in the abandoned gob are significantly different from those in a normal mining gob. In connection with this, this study physically simulated the movement of overlying rock strata. A spatial distribution function for gob permeability was derived. A numerical model using FLUENT for abandoned gob methane drainage through surface wells was established, and the derived spatial distribution function for gob permeability was imported into the numerical model. The control range of surface wells, flow patterns and distribution rules for static pressure in the abandoned gob under different well locations were determined using the calculated results from the numerical model.
Highlights
Methane remaining in the gob on cessation of underground coal mining operations is defined as abandoned gob methane (AGM)
A numerical model using FLUENT for abandoned gob methane drainage through surface wells was established, and the derived spatial distribution function for gob permeability was imported into the numerical model
The overlying strata are divided into three zones [13]: the gas conductive fracture zone (GCFZ), the gas pressure relief and desorption zone (GPRDZ), and the difficult desorption zone (DDZ) (Fig 2)
Summary
Methane remaining in the gob on cessation of underground coal mining operations is defined as abandoned gob methane (AGM). The USA investigated the methods to evaluate the potential of AGM drainage [6]. Strata description of AGM, but there is little concern on gas seepage characteristics in abandoned gob. This paper investigated the gas seepage characteristics in the abandoned gob where surface well drainage was conducted. A spatial distribution function for the vertical displacement of the overlying strata in a gob was proposed. On this basis, a spatial distribution function for gob permeability was derived. A numerical model using FLUENT for abandoned gob methane drainage through surface wells was established, and the derived spatial distribution function for gob permeability was imported into the numerical model. The control range of surface wells, flow patterns and distribution rules for static pressure in a gob under different well locations were determined using the calculated results from the numerical model
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