Directional drilling technology and equipment for gas drainage in large panel of underground coal mines

In recent years, with the progress of directional drilling technology and equipment in underground coal mines, a new model of advanced and comprehensive control of gas in the large panel of Baode Coal Mine is formed by covering the whole work with ultra-long directional drilling along the coal seam, hence the panel of the unexcavated roadway can be fully pre-pumped in advance to avoid gas overrun. As gas extraction in large panel requires a single construction along the coal seam borehole to run through the whole working face length, this paper starts from the construction technology of ultra-long directional drilling along the seam, introduces several key techniques of ultra-long directional drilling along coal seam, including progressive drilling trajectory extension technology, compound drilling trajectory control technology, hydraulic pressure drag reduction drilling technology, forward and reverse torsional drag reduction drilling technology and compound sidetracking branching technology and so on. It also introduces the main equipment for the construction of ultra-long directional drilling along coal seam, such as ZDY15000LD high power directional drill, BLY460/13 mud pump truck, YHD3-3000 mud pulse measuring system, wireless large hole drill pipe, hydraulic pressure screw motor and so on. The technology and equipment of ultra-long directional drilling for gas drainage along coal seam in large area are demonstrated and applied in the second block of Baode Mine. The application results show that this set of technology and equipment is capable of constructing ultra-long directional boreholes with a length of more than 3 300 m down the coal seam. Finally, the gas extraction effect is investigated, and the results show that the ultra-long directional borehole has a long extraction period and a high extraction amount, which can provide comprehensive gas management in the large pannl area in advance.