孕镶金刚石钻头优化设计及其在甘青隧道应用

Impregnated Diamond Bit Optimal Design and Application in GanQing Tunnel

孕镶金刚石钻头是通过胎体超前磨损,促使金刚石出露形成微切削刃,在钻压和扭矩的作用下对岩石进行磨削碎岩,可广泛应用于硬地层和复杂地层钻进。然而,常规金刚石钻头存在坚硬地层钻速低、进尺慢、费用高等问题。本研究首先采取甘青隧道S2Z-45钻孔相邻孔不同深度的岩石样品,对其硬度、矿物组成及可钻性进行测试分析,确定了岩层大部分以闪长岩为主,岩石可钻性等级为8级;然后针对甘青隧道的地质特点对孕镶金刚石的胎体硬度和底唇面形状进行了优化设计,并进行了现场试验,通过分析钻头的实际使用情况研究了孕镶金刚石钻头性能的影响因素。试验结果表明:胎体硬度为HRC 15~20、金刚石粒度40~50目、金刚石体积分数为20%、底唇面为环槽尖齿型的孕镶金刚石钻头性能最佳,寿命达到321 m,钻速为1.17 m/h;在相同金刚石参数下,胎体硬度为HRC 10~15的滚齿型孕镶金刚石钻头在钻速方面具有优势,最大钻速能够达到1.44 m/h。环槽尖齿型底唇面和高胎体硬度有助于提高钻头寿命,滚齿型底唇面和低胎体硬度有利于提高钻进效率,但钻头寿命偏低。

The impregnated diamond bit is a micro-cutting edge formed by exposing diamond in the matrix,and realizes the drilling of broken rock by crushing and grinding the rocks under the action of drilling pressure and torque.It can be widely used in hard formation and complex formation drilling.However,conventional diamond drill bits have problems such as low drilling speed,slow footage and high costs in hard formations.Firstly,rock samples,which were sampled in different depths form holes adjacent to the borehole S2Z-45 in GanQing tunnel,were taken for testing and analysis of their hardness,mineral composition,and drillability.It was determined that most of rock layers were mainly diorite,and the rock’s drillability level was eight.Then,according to the geological characteristics of Ganqing tunnel,the matrix hardness and bottom lip shape of impregnated diamond were optimized.The influencing factors of the performance of impregnated diamond bit was analyzed by field tests.The experimental results showed that the impregnated diamond bit had the best performance when its matrix hardness was HRC 15-20,a diamond particle size was 40-50 mesh,the volume fraction of diamond was 20%,and a bottom lip with a ring groove sharp tooth shape.It has a lifespan of 321 m and a drilling speed of approximately 1.17 m/h.Under the same diamond parameters,the hob type impregnated diamond bit with a matrix hardness of HRC 10-15 had advantages in drilling speed,which the drilling speed of the drill bit could reach 1.44 m/h.The sharp tooth bottom lip surface of the ring groove and high matrix hardness helped to improve the life of the drill bit,while the rolling tooth bottom lip surface and low matrix hardness were beneficial for improving drilling efficiency,but the life of the drill bit was relatively low.