Sampling technology for measuring gas content in coal seam with long distance fixed-point pressure sealing in underground mine

Li Quanxin; Fang Jun; Xu Chao; Liu Fei

doi:10.13199/j.cnki.cst.2017.07.013

Abstract：According to the low depth coal sampling,low accuracy,gas easy escape and other disadvantages existed in the available gas content test technology applied in the underground mine,the directional drilling technology and the closed coring technology were combined and applied to develop a coal sampling method from a long distance pressure maintained and closed sealing fixed point of the directional borehole based on the underground mine.The method would firstly have a long distance accurate drilling with a directional drilling to the coal sampling point and then a closed sampling device in seam was applied to make a pressure maintained and closed sealing coal sampling,mainly including the design of the coal sampling directional bnrehole,construction of the casing borehole section and directional borehole section,a single point coal sampling and a borehole multi sampling and other technical procedures.A matched drilling and sampling equipment was selected and equipped.A site trial was conducted in a mine at Jiaozuo.The results showed that the modified and improved technical method and equipment were applied to successfully complete five coal samplings with a coal sampling rate of 100％,successful pressure maintaining and closed sealing rate of 100％ and a max sampling depth of 491 m.The max sampling depth was over six times of the available technical sampling depth.There was a deviation less than 0.5％ between the actual sampling point the designed location.The accuracy of the coal sampling in the underground mine was obviously improved and the gas escape was reduced to ensure the test accuracy of the seam gas parameters and to provide the accurate reference basis to the engineering design and evaluation of the mine.