In order to solve the problem of the blindness of borehole layout when the nonuniform occurrence of gas and the neglect of plastic failure around the borehole will underestimate the gas production, a gas–solid coupling model is established for considering plastic failure. The finite element software COMSOL Multiphysics is used to investigate the evolution of the effective radius during the nonuniform occurrence of gas, and the relationship between the effective radius and the borehole spacing is determined. The results show that the permeability around the borehole increases significantly when plastic failure is considered and the rising area is butterfly shaped, with a maximum increase of 94 times. Not only does the peak value of the gas drainage flow increase but the time of its occurrence is also delayed. The maximum gas drainage flow rate increases by 40.7%, and the cumulative drainage volume increases by 37%. The relationship between the effective radius and reasonable borehole spacing in nonuniform gas occurrence is obtained. This research can provide a reference for the selection of borehole spacing under the condition of nonuniform distribution of coal seam gas.

中文翻译：

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瓦斯不均匀赋存及钻孔塑性破坏条件下有效半径的确定

为了解决因瓦斯赋存不均匀以及忽略井眼周围塑性破坏而导致低估瓦斯产量时钻孔布置的盲目性问题，建立了考虑塑性破坏的气固耦合模型。利用有限元软件COMSOL Multiphysics研究了气体非均匀赋存过程中有效半径的演化过程，确定了有效半径与井眼间距的关系。结果表明，考虑塑性破坏时，井眼周围渗透率显着增加，上升区域呈蝶形，最大增加了94倍。不仅瓦斯抽采流量峰值增大，而且出现时间也延迟。瓦斯最大抽放流量增加40.7%，累计抽放量增加37%。得出了瓦斯不均匀赋存时有效半径与合理井距的关系。该研究可为煤层瓦斯分布不均匀条件下井距的选择提供参考。