碎软煤层钻进钻杆槽体结构优化与工程应用

Optimization and Engineering Application of Drilling Rod Trough Body Structure in Fragmented Soft Coal Seams Drilling

高瓦斯碎软煤层具有煤体强度低、瓦斯含量高等特征,钻进过程中钻孔变形量大、易失稳破坏形成塌孔,导致钻孔深度浅、钻进效率低,进而影响了瓦斯抽采效率。为了提升刻槽钻杆在碎软煤层的应用效果,考虑螺旋槽体头数、螺距、槽深与槽宽等关键参数,采用EDEM与Fluent气固相间耦合的数值计算方法,构建刻槽钻杆钻进排渣模型,对比分析了刻槽钻杆的结构参数对排渣性能的影响。结果表明,增加螺旋槽体的头数,有利于增大排渣空间,提升钻杆的排渣效果;对于Ф50 mm的小直径刻槽钻杆,钻杆表面螺旋槽体设计为三头结构,相比单头和双头槽体,其排渣性能有明显提升;三螺旋刻槽钻杆螺距设计为252 mm、槽深为2.5 mm、槽宽为16 mm时,钻杆的排渣效果最优。通过现场工业性试验,钻进效果与煤矿使用的圆钻杆进行对比,三螺旋刻槽钻杆钻进深度提高11.5%,钻进效率提高35.4%,成孔率达到100%,在钻孔施工的过程中断钻、卡钻等打钻事故均未发生。

High gas fragmented soft coal seams have the characteristics of low coal body strength and high gas content.During the drilling process,the deformation amount of the borehole is large,and it is prone to instability and damage,resulting in collapse of the borehole.This leads to shallow drilling depth and low drilling efficiency,which affects the efficiency of gas extraction.In order to improve the application effect of grooved drill rods in fragmented soft coal seams,key parameters such as the heads number of spiral trough body,pitch of screw,trough depth,and trough width are considered.A numerical calculation method of gas-solid interphase coupling with EDEM and Fluent is used to construct a slag discharge model for grooved drill rods,and the influence of structural pa-rameters of grooved drill rods on slag discharge performance is compared and analyzed.The results show that increasing the heads number of the spiral trough body is beneficial for increasing the slag discharge space and improving the slag discharge effect of drill rods;for a Ф50 mm small diameter grooved drill rod,the spiral trough body on the surface of the drill rod is designed as a three headed structure,which significantly improves its slag discharge performance compared to single headed and double headed troughs;when the design of screw pitch of the triple helix grooved drill rod is 252 mm,the trough depth is 2.5 mm,and the trough width is 16 mm,the slag discharge effect of the drill rod is optimal.Through on-site industrial experiments,the drilling effect is compared with that of circular drill rods used in coal mines.The drilling depth of the triple helix grooved drill rod is in-creased by 11.5%,the drilling efficiency is improved by 35.4%,and the hole completion rate reaches 100%.During the drilling process,there is no phenomenon of jamming or breakage of drill rods happens.