超高压射流钻头破岩特性及设计

Rock Breaking Characteristics and Design of Ultra-high Pressure Jet Drilling Bit

为提高井下钻头射流压力,设计超高压射流钻头,基于光滑粒子流体动力学理论及钻头设计方法,开展了超高压水射流作用下岩石破碎特性分析,设计并加工了配套超高压钻头,并进行了现场试验。结果表明:随着水射流不断侵彻,破碎坑直径和深度逐渐增加,射流的回弹扩散效应是决定水射流破碎坑直径的重要影响因素。高压水射流冲击岩石产生的第一主应力显著高于岩石抗拉强度,第一主应力极大值主要分布在破碎坑表面。超高压PDC钻头为六刀翼式钻头,采用双锥轮廓,主切削齿后面布置较小PDC复合片切削齿,超高压喷嘴的位置位于PDC切削齿所在刀翼后面,出口角度为沿钻头旋转方向向前13°;超高压射流钻头试验结果表明,平均机械钻速同比提高了71.95%,提速效果显著。

Based on the smoothed particle hydrodynamics(SPH)theory and drill bit design method,the rock breaking characteristics of ultra-high pressure water jet were analyzed,the matching ultra-high pressure drill bit was designed and processed,and field experiments were conducted.The results indicate that as the water jet continuously penetrates,the diameter and depth of the broken pit gradually increase,and the rebound diffusion effect of the jet is an important factor affecting the broken pit diameter of the water jet.The first principal stress generated by high-pressure water jet impact on rocks is significantly higher than the tensile strength of rocks,and the maximum value of the first principal stress is mainly distributed on the surface of the broken pit.The ultra-high pressure bit is a six-blade bit with a row of smaller PDC composite cutters positioned behind the main cutters.The ultra-high pressure nozzle is positioned behind the PDC cutter and the blade,and the outlet angle is 13°forward along the bit rotation direction.The test results of ultra-high pressure jet bit showed that the average rate of penetration(ROP)was increased by 71.95%compared with the adjacent well under the same operating condition.