Key technology of drilling with ultra-long-distance directional hole for gas drainage along coal seam

In view of the shortcomings of existing coal mine underground directional drilling technology and equipment for ultra-long-distance directional hole above 3 000 m along coal seam,it is proposed to use ZDY15000 LD high-power directional drilling rig and BLY460 high-pressure mud pump truck to improve the drilling capaci ty of equipment,reduce the pressure consumption of flushing fluid by optimizing the flushing fluid pipeline of drilling system and developing drilling tools with large hole,r easonably set the operation parameters of mud pulse wireless MWD measurement system to improve the signal transmission stability under ultra-long-distance hole co ndition,and to achieve the flushing fluid of directional drilling by using underground flushing fluid purification and circulation system recycling. At the same time,it has in novatively developed key technologies for ultra-long-distance directional hole drilling such as sliding drilling drag reduction technology,compound drilling inclination cont rol technology and compound drilling sidetracking branch technology. Combined with the need of advanced control of coal seam gas in large area of Baode Coal Mine 0 f Shendong Coal Group,the practice of ultra-long distance directional drilling along the coal seam with a depth of 3 000 m or more was carried out,and an ultra-long-dist ance directional drilling along the coal seam with a main hole depth of 3 353 m was created. The practice results show that: the ultra-long-distance directional drilling e quipment system has effectively improved the deep hole drilling capacity of coal mines,reduced the mud pump pressure during drilling,realized the stable transmission of measurement signal under the condition of ultra-long-distance hole,reduced the amount of clean water and sewage discharge during directional drilling; the develope d key technologyof ultra-long-distance directional hole dillingreduced the resistance of sliding directional dilling,improved the depth of sliding directional dilligndrillig efficiency and the application proportion of compound dilling,and solved the problem of dilling branch hole inside the super long hole.