平行钻孔有效抽采半径及合理钻孔间距研究

Research on effective drainage radius and rational borehole spacing of parallel boreholes

为确定平行钻孔瓦斯抽采合理钻孔间距,通过推导煤层瓦斯运移方程、煤岩体变形方程及渗流场与应力场耦合方程,建立了瓦斯抽采流固耦合模型;根据某矿21219工作面实际地质条件,利用COMSOL Multiphysics软件对平行钻孔间抽采叠加效应影响下瓦斯压力、有效抽采半径的变化规律进行了数值模拟研究,并结合钻孔有效抽采半径,得出了合理的钻孔间距。数值模拟结果表明,随着钻孔间距的增大,抽采后煤体瓦斯压力增大;随着煤体距钻孔距离减小,煤体瓦斯压力呈先缓慢减小、后快速下降的趋势;随着抽采时间的增加,瓦斯压力不断降低,钻孔有效抽采半径变大。现场应用结果验证了钻孔间距布置的合理性。

In order to determine rational borehole spacing of parallel boreholes for gas drainage, a fluid-solid coupling model of gas drainage was established by deducing gas migration equation of coal seam, deformation equation of coal and rock, and coupling equation of seepage field and stress field. According to actual geological conditions of 21219 working face in a mine, variation law of gas pressure and effective drainage radius under influence of drainage superposition effect between parallel boreholes were numerically simulated by COMSOL Multiphysics software, and rational borehole spacing was obtained by combining with effective drainage radius of borehole. The numerical simulation results show that gas pressure of coal body after drainage increases with the increase of borehole spacing. As the distance between coal body and borehole decreases, gas pressure of coal body decreases slowly at first and then decreases rapidly. With the increase of drainage time, gas pressure decreases continuously and effective drainage radius increases. The field application results verify rationality of borehole spacing arrangement.