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 sect