叠加效应影响下钻孔有效抽采半径的数值模拟及布孔间距优化

针对煤层瓦斯预抽钻孔布孔间距存在盲目性和不确定性等问题,以流固耦合原理为基础构建煤层瓦斯抽采流固耦合数学模型,借助FLUENT数值模拟软件对煤层瓦斯预抽钻孔有效抽采半径进行数值模拟研究,在多钻孔数值模拟的基础上对建新煤矿4207工作面煤层瓦斯预抽钻孔布孔参数进行了优化。结果表明:钻孔有效抽采半径随抽采时间的增加呈对数形式增大;多钻孔抽采时孔间相互扰动可产生抽采叠加效应,布孔间距越密集,钻孔之间瓦斯压力下降幅度越显著;在90 d的预抽期内,建新矿单孔抽采的有效半径为2.02 m,多孔抽采的布孔间距为2.86~4.50 m。结合煤层厚度提出了正三角形的布孔方式,经现场应用瓦斯参数达标,布孔方案切实有效。

Numerical simulation of effective drainage radius and optimization of hole spacing under the influence of stack effect

In view of the problems such as blindness and uncertainty existing in the hole spacing for pre-drainage of coal seam gas,a mathematical model of solid-liquid coupling for coal seam gas drainage was established based on the principle of solid-liquid coupling,and then the effective drainage radius of drilling in pre-drainage of coal seam gas was studied by numerical simulation with the help of FLUENT numerical simulation software.Based on the numerical simulation of multiple holes,the layout parameters of pre-drainage hole of coal seam gas in 4207 working face in Jianxin Coal Mine were optimized.The results show that the effective extraction radius increases in logarithmic form with the increase of extraction time;the mutual disturbance between holes can produce stack effect when drilling with multiple holes,the denser the spacing between holes,the more significant the decrease of gas pressure between boreholes;in the pre-drainage period of 90 d,the effective radius of single hole extraction is 2.02 m,and the spacing of multiple holes extraction is between 2.86 m to 4.50 m.Based on the thickness of coal seam,the equilateral triangle hole layout scheme is put forward.The gas parameters are up to standard and the hole layout scheme is effective in field application.