基于不同钻孔间距的瓦斯抽采效果实验研究

Experimental study on gas extraction effect with different borehole spacing

为了研究钻孔布置对瓦斯抽采效率的影响,采用自主研发的多场耦合煤层气开采物理模拟实验系统,开展了不同钻孔间距条件下瓦斯抽采物理模拟实验研究,探讨了钻孔间距对瓦斯抽采效果的影响。结果表明:在抽采初期,各测点瓦斯压力下降速率和下降量主要受到离钻孔中心距离的影响,与测点距钻孔出口距离基本无关,在瓦斯抽采过程中,靠近钻孔中心位置的瓦斯压力梯度大,瓦斯流速也较大,断面瓦斯压力场中等压线以钻孔为中心呈圆环形分布;相邻钻孔之间产生的抽采叠加效应会影响有效抽采范围,钻孔间距越近,有效抽采范围越大,同时其有效抽采范围也随抽采时间呈指数型增长。

In order to study the influence of borehole layout on gas extraction efficiency,the physical simulation test of gas extraction under different borehole spacing conditions is carried out using the self-developed multi-field coupled physical simulation test system for coalbed methane production,and the influence of borehole spacing on gas extraction effect is discussed.The results show that in the early stage of gas extraction,the rate and quantity of gas pressure drop at each measuring point are mainly affected by the distance from the borehole center,which is basically independent of the distance between the measuring point and the borehole outlet.In the process of gas extraction,the gas pressure gradient near the borehole center is large,the gas flow velocity is large,and middle pressure line of cross-section gas pressure field is distributed in circle centered on boreholes.The superposition effect of extraction between adjacent boreholes will affect the effective extraction range.The closer the distance between boreholes is,the larger the effective extraction range is.At the same time,the effective extraction range also increases exponentially with the extraction time.