Meikuang Anquan (Oct 2022)
Effective drainage area and parameter optimization of bedding drilling in high gas and thick coal seam
Abstract
In order to study the effect of different parameters on drainage effect of bedding drilling in high gas coal seam, based on Fick diffusion, Darcy’s law, ideal state gas equation and Langmuir equation, the flow-solid coupled mathematical model of gas-water two-phase flow of gas-water were established by combining the fracture-pore dual pore medium structure of coal mass and the transport characteristics of gas and water. The COMSOL Multiphysics software was employed to conduct a numerical simulation study on gas extraction of the 3# coal seam in Zhangcun Coal Mine. The results present that the larger the drill hole diameter in a certain range, the higher the extraction efficiency will be. The effect of the change of negative extraction pressure on the effective area of gas extraction and the change of gas pressure is significantly weak and the improvement of gas extraction efficiency is not much. Reducing the spacing between boreholes can effectively improve the extraction efficiency, however it is not the case that the smaller the spacing between boreholes, the better effect will be. In the early stage of extraction, the effective extraction area of each drill hole is independent. As the extraction progresses, the effective extraction zone of each drill hole gradually increases and is superimposed on the effective extraction zone of adjacent drill holes to form an overall effective extraction zone. When it is required to reach the standard within 100 days of extraction, the optimal plan for single hole arrangement of 3# coal seam in Zhangcun Coal Mine is 94 mm in diameter, 20 kPa in negative extraction pressure and 3 m in spacing.
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