旋切式PDC钻头水力结构优化

旋切式PDC钻头比常规PDC钻头的结构更复杂,工作原理也比较特殊,常规的数值模拟方法不能全面描述旋切式PDC钻头水力结构及井底流场特性。鉴于此,采用标准k-ε模型和离散相模型(DPM)对旋切式PDC钻头井底流场进行仿真模拟,并对钻头的水力结构进行优化设计,对优化前后旋切式PDC钻头的井底流场进行对比分析。研究结果表明:刀盘形状的改变有利于工作流体的流动,可以降低刀盘附近岩屑颗粒的质量浓度;采用带有曲率的喷嘴可以增强旋切式PDC钻头刀盘区域的井底清洗效果;当采用曲率为1/50的喷嘴时,刀盘区域的井底清洗效果最好;当采用中心喷嘴直径12.0 mm和边缘喷嘴直径8.8 mm的组合方案时,旋切式PDC钻头的清洗和携岩能力达到最优。研究结果对未来页岩气开采方式的研究具有一定的指导意义。

Optimization of Hydraulic Structure of Rotary Cutting PDC Bit

Few researches have been conducted on the hydraulic structure optimization design of rotary cutting PDC bit.Standard k-εmodel and discrete phase model(DPM)are used to simulate the bottom hole flow field of rotary cutting PDC bit and optimize the hydraulic structure.The bottom hole flow field of the rotary cutting PDC bit before and after optimization is compared and analyzed.The results show that the change of the shape of the cutter plate is beneficial to the flow of fluid and can reduce the mass concentration of the cutting particles near the cutter plate.The use of bit nozzle with curvature can enhance the bottom hole cleaning effect of the cutter plate area of rotary cutting PDC bit.A nozzle with a curvature of 1/50 provides the best bottom hole cleaning effect at the cutter plate area.The combination of the 12.0 mm center nozzle and the 8.8 mm edge nozzle presents the best cleaning and cutting carrying capacity of the rotary cutting PDC bit.The study has certain guiding significance for the future researches on shale gas development.