Key technology of high efficeiency hole formation for ultra deep directional hole with long 2 570 m along seam in underground coal mine

In view of the problem that the existing directional drilling technology and equipment can not meet the requirements for the depth of in-seam directional borehole in the large area of gas control in the ultra long working face. It is proposed to use the mud pulse wireless MWD system instead of the wired MWD system to measure the drilling parameters, so as to avoid the problem that the signal transmission of the wired MWD system is affected by the cable drill pipe.Based on the theory of “cuttings wedge” in rotary drilling of near horizontal borehole, the inclination of increase, decrease and balance borehole angle under the condition of compound drilling is adjusted through optimizing the structure of DHM and adjusting the drilling parameters,which further improves the proportion of compound drilling footage and makes the drilling system pressure significantly lower.In combination with the production needs of Baode Coal Mine, the in-seam ultra-deep directional borehole with the depth of 2 570 m and the diameter of 120 mm is completed, and the average daily drilling footage is more than 200 m.According to the adaptability analysis of the key equipment of the ultra-deep borehole, it can be seen that the drilling equipment is stable and reliable, the signal transmission of wireless MWD system is stable in the ultra deep drilling, the angle control effect under the condition of compound drilling is good, and the system pressure parameter drops obviously, which shows that the technical equipment can meet the construction requirements of the ultra deep directional drilling of 2 500 m coal seam under the full coal mine.It provides an important reference for the construction of ultra deep directional drilling along the coal seam and the advanced gas control in the ultra long working face.The drilling process shows that the drilling equipment is stable and reliable, the signal of wireless MWD system is stable in the ultra-deep borehole, the angle of control inclination of compound drilling is effective, and the pressure parameters of the drilling system is obviously reduced. It shows that the technology and equipment can meet the construction requirements of the in-seam ultra-deep directional borehole beyond 2 500 m underground coal mine.The research can provide an important reference for the construction of in-seam ultra-deep directional borehole and the comprehensive advanced control of gas in the area of ultra-long working face.