Abstract: To improve the drilling efficiency in some hard rock and abrasive formations and reduce cuttings accumulation in the bottom hole, the structure is adjusted based on the traditional PDC ( Polycrystalline Diamond Compact) drill bit. There is no central nozzle and three inclined nozzle holes with an axial angle of 20°are set, changing the six blades distribution. Using the numerical simulation analysis method and adopting the SST k-ω model, the characteristics of the jet flow field of the PDC bit are studied, and the jet flow velocity and pressure gradient of the bottom hole, nozzle and blade surface are numerically analyzed. On this basis, the hydraulic parameters are optimized again, and the bottom hole flow field of the PDC bit with different parameters is analyzed and compared. The results show that:The smaller the diameter of the drill bit nozzle, the greater the velocity of the direct shot point, which is more conducive to rock cutting, but the hydraulic energy is too concentrated to fully cover the bottom of the well by high-speed flooding, which is not conducive to cleaning the cuttings. When the axial is 20°-30°, the axial angle of the drill nozzle will increase, and the velocity of the direct shot point will not change much, but the vortex at the shoulder of the drill bit will decrease, and the speed in the upward return area will increase, which is conducive to the rapid discharge of cuttings from the bottom of the hole. And the surface of the blade is not easy to produce bit balling. When the nozzle diameter of the drill bit is 24 mm-28 mm, and the nozzle axial angle is 25°-30°, the PDC drill bit has the best hydraulic performance.

Key words: PDC bit, bottom hole flow field, numerical simulation, nozzle, cuttings

摘要： 为了提高在某些硬岩和研磨性地层钻进效率，减少井底岩屑堆积，基于传统PDC（ 聚晶金刚石复合片）钻头进行了结构调整，无中心喷嘴，设置三个轴向夹角为20°的斜喷嘴孔， 改变六刀翼分布。利用数值模拟分析方法，采用SST k-ω模型，对PDC钻头射流流场特性进行研究，分别对井底、喷嘴、刀翼表面射流流速和压力梯度进行了数值分析。在此基础上，对其水利参数再次优化，并对不同参数的PDC 钻头井底流场进行分析对比。 结果表明，钻头喷嘴直径越小，直射点速度越大，越利于破岩，但水力能量过于集中，高速漫流无法充分覆盖井底，不利于清洗岩屑；轴向夹角度数在20°～30°时，钻头喷嘴轴向夹角度数变大，直射点速度变化不大，但钻头肩部涡旋减少，上返区域速度提高，有利于岩屑快速排出井底，刀翼表面不易产生泥包；当钻头喷嘴直径在24 ~ 28 mm，喷嘴轴向夹角度数在25° ~ 30°时，该PDC钻头水力情况最佳。

关键词: PDC钻头, 井底流场, 数值模拟, 喷嘴, 岩屑