Study On The Regularity Of Trajectory Offset Of Long Borehole In High Gas Drainage In Shanxi Detong Coal Mine

Coal mine gas accidents in China have occurred from time to time,which has seriously affected the healthy and sustainable development of coal mining enterprises.Gas control is the premise of safe production in coal mines.Gas drainage is the fundamental measure to control coal mine gas.Downhole drilling technology in coal mines is an effective means to improve gas drainage efficiency.In the construction process,drilling trajectory control is the focus of directional drilling technology.Therefore,it is of great significance to study the law of directional drilling trajectory deviation.This paper mainly relies on the long-hole drilling project of high gas drainage in Detong Coal Mine,and takes the trajectory design,optimization and control of the long-oriented drilling as the research object,and analyzes the influence factors(traces and geology)of the traditional long-directional borehole trajectory.Based on the above,the trajectory of long boreholes was optimized,and the main influencing factors of borehole trajectory in the study area were summarized.In the skein section,by analyzing the data of the difficult-to-control boreholes in the test borehole,combined with the influencing factors of the borehole trajectory,FLAC3D was used for numerical simulation to study the stress distribution,displacement vector and displacement cloud map of the drilled formation,and the qualitative assessment was made.Drill hole trajectory.In the near-horizontal section,a mixed drilling technique test was performed on directional drilling,and the law of deviation of the drilling trajectory by the rotary drilling technology was explored.The results show that:(1)In the whipstocking section,the factors affecting the long trajectory of high-directional gas drainage in the Detong coal mine are soft and hard interbeds,and the vertical depth of the difficult-to-control hole section is 35m to 40m.When the hard rock enters the soft rock,the rock strength of the hard rock is relatively large,so that the drilling tool can not be staggered according to design requirements,resulting in the deviation of the actual drilling path from the design track;(2)Numerical simulation analysis The location where the force is exerted on the end of the drill pipe is concentrated in the stress.The plastic deformation zone of the drill hole is mainly located at the contact area between the drill bit and the rock.The stress of the hard rock part is relatively large,preventing the inclination angle from changing,resulting in the deviation of the drilling trajectory.(3)In the near-horizontal section,the factors affecting the directional long borehole trajectory are drilling methods.The rotary drilling technology is used to perform the 40?50m rotary drilling test.The change of inclination angle is between 1°and 2°,and the change of azimuth angle is about 1°.The research results can guide the drilling construction in the later stage of the study area,improve the drilling efficiency and accuracy,and have certain significance for high-position directional drilling in other similar areas.