顺层钻孔布置间距对煤层瓦斯抽采效果影响的物理模拟试验研究

Physical simulation experiment on influence of borehole spacing along the seam on effect of gas drainage

基于自主研发的多场耦合煤层气开采物理模拟试验系统,开展了不同顺层钻孔布置间距条件下的瓦斯抽采物理模拟试验,对瓦斯抽采过程中煤层瓦斯压力及抽采流量的演化规律进行了探讨。研究结果表明:煤层内不同测点的气压随着与抽采管之间距离的减小,下降速率加快;当受抽采叠加效应影响时,在相同距离条件下抽采管之间区域的气压下降速率大于外侧,且在抽采开始后该气压差异迅速到达峰值后呈下降趋势,而距离抽采管越近的区域,或随钻孔布置间距增加,叠加效应均减弱;在煤层垂直于钻孔的断面上,气压梯度与抽采瞬时流量存在幂函数关系,随着钻孔布置间距减小,或数量增加,同一位置的气压下降速率增大,抽采瞬时流量下降速率加快,累计流量增加,煤层渗透性系数ɑ值增大,说明煤层瓦斯抽采效率更高。研究结果可为现场合理布置抽采钻孔提供一定的理论依据。

Based on the self-developed multi-field coupling testing system for coalbed methane exploitation, a series of physical simulation experiments of gas drainage under different spacing distances between boreholes was conducted to investigate the evolution of gas pressure and gas flow rate during drainage process. The results show that the gas pressure at different measuring points in the coal seam drops faster with the decrease of the distance from the drainage pipe. With the influence of the drainage superimposed effect, the gas pressure drop rate of areas between the drainage pipes is greater than that of the outside under the same distance condition, and the pressure difference rapidly reaches the peak value after the start of drainage, and then drops. The closer to the drainage pipe or with the increase in the borehole spacing, the less the effect of the superimposed effect is. There exists a power function relationship between pressure gradient and instantaneous flow rate on the section of the coal seam perpendicular to the borehole. With the increasing amounts or decreasing spacing of boreholes, the gas pressure of the same position drops faster, the instantaneous flow rate decreases, the cumulative flow rate increases, and the value of coal seam permeability coefficient "ɑ" increases, indicates that the gas drainage efficiency is higher. It can provide theoretical basis for reasonable arrangement of boreholes.