关于PDC钻头形态设计的探讨

Investigation in shape design of PDC bit.

针对原有PDC钻头井底流场存在局部流速过大而对钻头表面造成破坏 ,局部流速过小容易产生泥包的问题 ,对原有钻头做如下结构改进 :增加大胫板的长度 ;降低胫板的高度和减小宽度 ;增加小胫板的数量 ,同时减小水槽截面积。对改进的钻头结构建立井底流动模型 ,并进行数值模拟。分析改进结构的流场表明 ,新结构钻头井底流场分布更合理 ,减少了流体对钻头中心区的直接冲蚀 ,有利于延长钻头寿命 ;合理降低切削齿高度后 ,加大了井底漫流区面积 ,提高了切削效率。

During the using of the traditional PDC bit, the bit surface will be destoryed if the local flow rate of the flow field of the bit is too large, and balling up may occur if the flow rate is too small. To overcome this shortcoming, the structure of the bit is modified as follows: extending the length of the big cutter, decreasing the height and width of the cutter; increasing the number of the small cutter and decreasing the sectional area of the gutter. A bottomhole flow model for the modified bit is built up, and numerical simulation is conducted. The flow field of the bit with modified structure shows that, the bottomhole flow field of the new bit distributes more rationally, therefore the direct abrasion of the fluid on the center area of the bit is decreased, and this is helpful to extending the bit's lift. On the other hand, with the cutting height lowered properly, the area of the bottom hole overflow part is enlarged, thereby the cutting efficiency is improved.