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

According to the low depth coal sampling, low accuracy, gas easy escape and other disadvantages existed in the available gas content test technology a pplied 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 dis tance 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 C losed sealing coal sampling, mainly including the design of the coal sampling directional borehole, 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 equip ped. 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 successully C omplete 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. T he 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 desig ned 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 s eam gas parameters and to provide the accurate reference basis to the engineering design and evaluation of the mine.