瓦斯抽采钻孔漏气通道检测装置研制及应用

瓦斯抽采钻孔孔周裂隙和封孔段空隙通道是造成钻孔漏气失效的主要原因。为有效检测钻孔漏气通道,基于管流流体力学理论和漏气检测判别方法,研制了瓦斯抽采钻孔漏气通道检测装置。通过检测不同钻孔深度气样参数并分析其分布规律和突变情况,确定抽采钻孔失效原因和漏气通道位置;检测装置采用高稳压阻式压力传感器、激光甲烷传感器和荧光氧气传感器实现抽采负压、瓦斯浓度和氧气浓度检测,并采用1.5 m/节快接式25 mm薄壁不锈钢管作为取气管件,钻孔检测深度达30 m。现场应用结果表明,抽采管段检测参数变化稳定,说明抽采管未发生破损或接口漏气等,抽采管密封效果较好;在封孔段,距孔口9~18 m范围内存在多处不同程度的突变点,最大漏气通道在距孔口9~12 m范围内,说明原封孔深度不足,原封孔工艺无法有效密封漏气通道。将封孔深度增加至12 m,并采用“两堵一注”带压注浆封孔工艺,进行对比试验,结果表明,改进后试验钻孔整体抽采效果大幅改善,孔口瓦斯体积分数提升至55%以上,在距孔口12 m以深范围内瓦斯体积分数变化稳定,氧气体积分数近乎为0,漏气通道减少。试验结果验证了瓦斯抽采钻孔漏气通道检测装置能够有效检测漏气通道,为有针对性地调整封孔方式和相关参数及后续改进工作提供依据。

Development and application of gas leakage channel detection device for gas extraction borehole

The perimeter cracks of gas extraction borehole and the gap passage of sealing section are the main causes of the failure of borehole leakage.In order to detect the gas leakage channels in the borehole effectively,a gas leakage channel detection device is developed based on the theory of tube flow hydrodynamics and gas leakage detection method.Detecting gas sample parameters at different drilling depths and analyzing the distribution and abrupt changes are used to identify the cause of extraction borehole failure and the location of gas leakage channels.The detection device adopts highly stable piezoresistive pressure sensors,laser methane sensors and fluorescent oxygen sensors to detect extraction negative pressure,gas concentration and oxygen concentration.The device adopts 1.5 m/section quick-connect 25 mm thin-walled stainless steel pipe as the gas extraction fittings and the drilling depths is up to 30 m.The application results show that the variation of testing parameters in extraction pipe section is stable,the extraction pipe is not damaged,the interface is not leaking,and the sealing effect of the extraction pipe is good.In the sealing section,there are several abrupt change points of different degrees in the range of 9-18 m from the hole.The largest air leakage channel is in the range of 9-12 m from the hole,indicating that the original sealing depth is insufficient and the original sealing process cannot seal the air leakage channel effectively.In this study,the sealing depth is increased to 12 m and the'two plugging and one injection'pressure-injected grouting sealing technology is used for comparative tests.The results show that the overall extraction effect of the test hole is greatly improved,the volume fraction of gas at the hole is increased to more than 55%,the change of gas volume fraction is stable within the depth range of 12 m from the hole,the volume fraction of oxygen is almost 0,and the gas leakage channels are reduced.The test results verify that the gas leak channel detection device can effectively detect gas leakage channels,provide a basis for the targeted adjustment of sealing methods,related parameters and subsequent improvement.