Study On Gas Control Mechanism And Key Design Parameters Of Directional Drilling In Upper Corner Of Wangjialing Mine

The overburden mining fissure of the coal seam roof is the channel for the unloading gas seepage in the mining process.The high-level directional drilling is used to establish a gas drainage channel in the mining fissure zone of the coal seam roof,and the working surface and the goaf are free.Gas,to achieve the purpose of reducing the gas concentration of the corners on the working surface,making it an effective method to solve the gas over the coal mine.In recent years,high-level directional drilling has been widely used in the upper corner gas control and gradually become a mature technical means.Compared with the traditional high-drainage and high-level drilling,the unloading of the cut-off goaf and adjacent coal seams On the gas,high-directional directional drilling has obvious advantages in eliminating the upper limit of gas in the upper corner.However,in the engineering practice of the site,some key parameters of the high-level directional drilling are often designed according to the previous construction experience.There will still be some deviations in the application effect,resulting in poor drainage and ineffective work for field engineering practice.Therefore,this paper starts with the main factors affecting the effect of high-level directional drilling,and studies the key design parameters of high-level directional drilling.The research content of this paper mainly carries out the following four aspects:(1)Study on the development range of gas-guiding fracture zoneCombining theoretical analysis with numerical simulation,the developmental range of the gas-guiding fracture zone is studied.The theoretical analysis adopts the key layer theory to study from the top three zones of the strike and the three zones of the trend.The numerical simulation uses the two-dimensional discrete element numerical simulation software Udec to study the development height of the roof crack.Based on the results of comprehensive theoretical analysis and numerical simulation,the critical layer parameters of the subsequent high-level directional drilling design are optimized to determine the hole level of the borehole.(2)Gas drainage model for high-level directional drilling and determination of effective influence radiusThe gas migration law is analyzed from the rip belt,the fissure zone and the curved sag zone.The fractured zone of the roof slab and the gas filled in it form the porous media zone of the mining zone and the fracture zone of the goaf.The permeability coefficient of the area is assigned and a mathematical model of gas migration in the goaf is established.In addition,the influence radius of high-directional directional drilling gas drainage is determined.(3)Optimization of high-level directional drilling parametersFirstly,the factors influencing the effect of high-level directional drilling are analyzed,and the main factors of this paper are selected.Then the numerical model of high-directional directional drilling gas drainage is established by using Comsol software,and the main factors are analyzed.Influencing the law,and then the optimal key parameters of high-level directional drilling.(4)High-position directional drilling field applicationThrough the optimization research of high-level directional drilling parameters,the key design parameters of high-directional directional drilling after Comsol software modeling and numerical simulation optimization are obtained.The engineering practice is carried out in Wangjialing Mine,and the key parameters are verified from the later extraction of high-level directional drilling.The feasibility of the design.