煤矿井下可开闭式PDC钻头的设计与优化

Research and optimization of switchable bit used in coal mine underground

松软煤层瓦斯抽采钻孔施工完成后,为解决裸孔下筛管困难的问题,常采用不提钻下筛管工艺,即将筛管从钻杆内下入孔底。采用一次性脱芯钻头时,存在浪费和安全问题,为此需要设计可开闭式PDC钻头。研制的四翼可开闭式PDC钻头采用铰接式结构,用弹簧珠进行弹卡定位,中心翼片开闭灵活,且能重复利用,解决了脱芯钻头存在的问题,且在顺层钻孔中进行了试验,能够满足不提钻下筛管工艺要求。但在夹矸煤层及穿层孔钻进时,四翼可开闭式PDC钻头体易变形,导致中心翼片开闭困难,为此优化了钻头结构,采用三翼和半开放式凹槽结构,将中心翼片内嵌到钻头体内,提高钻头体整体强度,并调整了PDC切削齿排布方式,在穿层钻孔施工中,中心翼片开闭性能更可靠,明显提高了穿层孔不提钻下筛管的成功率。

In order to solve the problem that screen is difficult to be inserted after the drilling hole in the soft coal seam is completed,screen insertion without lifting the drill pipe was often used.When using a disposable depoling bit,there is a waste and security issues,switchable bit was needed to design.The drill bit is hinged-type structure,with spring beads for positioning.The center wing can be opened and closed flexibly and can be reused,which solved the problems of switchable bit.The drill bit was tested in the borehole drilling and can meet the requirements of the drilling process.But in the gangue coal seam and rock drilling,the bit wear deformation is serious leading to the wing is difficult to open.Therefore,the bit was optimized,three-wing and semi-open groove structure was used,the central wing was placed into the bit body,which improved the overall strength of the bit body,and the PDC cutting tooth arrangement was optimized.The bit has made a good trial effect in the drilling through rock,greatly improving the rate of screen insertion.