随着我国煤矿开采逐渐向深部开拓，煤层瓦斯压力增大、含量增加，煤层渗透率普遍较低，增加了瓦斯抽采的难度。钻孔钻扩造穴卸压增透技术能提高煤层渗透率，是增加瓦斯抽采效率的有效手段。为解决寺家庄煤矿15号煤层渗透率低，瓦斯难抽采的问题， 以寺家庄煤矿北翼辅助运输巷15号煤层抽采钻孔造穴为工程背景，以弹性力学应变软化模型和扩散-渗流煤层瓦斯流动理论模型为基础，建立了穿层钻孔钻扩造穴后煤层渗透率演化方程和穿层钻孔造穴煤层瓦斯流动方程。通过COMSOL Multiphysics多物理场数值模拟软件对方程进行解算，分析了钻孔造穴的增透机理和渗透率分布规律，得到了瓦斯抽采量、瓦斯压力分布以及渗透率等关键参数；结合模拟结论与现场条件，确定了钻孔钻扩造穴的最优造穴半径为0.6 m，最佳布孔间距为6.0～7.0 m，为现场施工造穴半径和钻孔间距的确定提供了指导。最后，在寺家庄煤矿15号煤层实施普钻钻孔与造穴钻孔，进行了瓦斯抽采效果对比。试验结果表明：实施水力钻扩造穴技术后，瓦斯抽采率、抽采浓度和抽采纯量相对普钻钻孔分别提高了约2.7、2.0、5.7倍；瓦斯抽采周期、钻孔施工工程量降低了约2倍，提高了瓦斯抽采技术经济效益,应用结果验证模拟结果可靠，抽采设计可行，可以指导现场施工。

As coal mining gradually extends to the deep level,the pressure and content of coal seam gas increase,and the permeability of coal seam is generally low,which increases the difficulty of gas extraction.The technology of pressure relief by cavity drilling is an effective method to improve the permeability of coal seam and the efficiency of gas extraction. Based on the engineering background of No.15 coal seam cavity drilling in the auxiliary transportation roadway of north-wing of Sijiazhuang Coal Mine,and according to the elastic mechanics softening model and diffusion-seepage coal seam gas flow theoretical model,the authors  established the evolution equation of coal seam permeability and the gas flow equation of cross-seam cavitation borehole. Using COMSOL Multiphysics software,the models were calculated,and the permeability increasing mechanism and distribution law after cross-seam cavitation borehole were analyzed. The gas extraction amount,gas pressure distribution and permeability were obtained. Combining the simulation results with field conditions,the optimal cavity radius was 0.6 m,and the optimal hole spacing was 6.0～7.0 m. It provided a guidance for the borehole radii and spacing in field construction. Finally,the conventional drilling and cavity drilling were carried out in No.15 coal seam of Sijiazhuang Coal Mine,and the gas extraction effect was compared. Results showed that the gas drainage rate,gas concentration and purity were increased by 2.7,2.0 and 5.7 times compared with the conventional drilling after the implementation of hydraulic cavity drilling technology. The period of gas drainage and the amount of drilling construction were reduced about 2 times,which improved the economic benefits of gas drainage technology. Thus,the simulation results are reliable and the gas drainage design is feasible,which can guide the field construction.

0 引言

1 钻扩造穴卸压增透机理及瓦斯流动模型

   1.1 钻扩造穴卸压增透机理

   1.2 瓦斯流动模型

2 模拟与结果

   2.1 模型描述和输入参数

   2.2 造穴半径对增透效果的影响

   2.3 钻孔间距对瓦斯抽采的影响

3 现场应用试验

4 结论