Research On Characteristics And Prevention Technology Of Gas Drainage Borehole

When mining coal seams,especially high gas and outburst coal seams,in order to reduce the gas pressure in the coal seam,people usually adopt the method of pre-draining gas drainage holes to relieve pressure.When the injection hole occurs,the injection hole will produce a large amount of gas and coal dust,which seriously affects the safe production of coal.Based on the starting point of ensuring the safe and efficient development of drilling operations,this paper takes the prevention and control of injection holes in gas drainage holes as the research goal,and studies the characteristics and prevention of injection holes from the aspects of theoretical analysis,numerical simulation,program optimization and equipment research and development.The specific research contents and results are as follows:(1)On the premise of analyzing coal and gas outbursts,the gas drainage boreholes and borehole injection holes are studied.The research contents mainly include the characteristics and hazards of the injection holes,the mechanical form of the drilling holes in the construction process,The process of injection holes,etc.;the injection holes are analyzed from the perspective of energy,the reasons for the occurrence of injection holes,the original energy in the coal seam before drilling and the external energy generated during drilling are analyzed,and the energy balance formula is established;the rotational speed of the drill pipe is clarified,drill pipe diameter,drill pipe advancing speed,etc.are important factors that affect the stability of drilling.(2)In order to find out the influencing factors of coal instability in the borehole and its specific influence,taking the Puxi well of Jiahe Mining as the research background,the finite difference analysis software FLAC3 D was used to analyze the coal loss in the gas drainage borehole.The simulation study was carried out steadily,and the displacement law and stress state of the coal body in the borehole under the conditions of different borehole diameters,different in-situ stresses,and different coal seam thicknesses were respectively studied.The more easily unstable the coal body is;the thicker the coal seam,the more stable the coal body in the borehole.(3)On the basis of theoretical analysis and numerical simulation,using the influencing factors,hazards and characteristics of blowholes,combined with the actual situation of the site,two optimization schemes are proposed for the drilling construction of Puxi Well,and the diameter of the drill pipe is selected.9 evaluation indicators such as drill pipe speed and economy,using AHP and multi-attribute decision-making analysis method to select two optimization schemes,and get the final optimization scheme and suggestions under comprehensive consideration.(4)In order to prevent the injection holes caused by the misoperation of workers and equipment failures during construction,the characteristics and hazards of the injection holes and the original drilling rig system on site have been used to develop gas collection prevention injection holes,gas and coal dust collection,dust reduction,etc.It is a device that integrates functions.The main components of the device include: anti-protrusion baffle,dust collection device,dust removal and slag discharge device,etc.;on the one hand,it can prevent the situation of spray holes;of gas and coal dust.The effect of the device in the downhole test is very significant.