脉冲空化PDC钻头的研究及应用

Design and Application of Pulse Cavitation PDC Bit

为解决现有脉冲射流钻井技术存在的脉冲发生部位离井底远、脉冲效应沿程损失大及在定向钻具组合中应用受限的问题,设计了一种脉冲空化PDC钻头。该钻头内腔设计成脉冲谐振腔结构,利用谐振腔各区域收缩面的不同,把进入的连续射流调制成脉冲射流;脉冲射流再经钻头空化喷嘴耦合,使作用于井底的脉冲效应最大化。井底流场和清岩效果分析结果表明:脉冲空化PDC钻头产生的脉冲作用对井底岩屑具有更好的翻转和运移效果,能使岩屑及时离开井底,减少重复切削;由于把脉冲发生部位置于钻头内部,离井底更近,不仅减少了脉冲效应的沿程损失,还不需要增加额外接头和专用装置等,能用于所有定向钻具组合,同时提高了钻柱的安全性。通过研究,形成了 215.9和 311.2 mm共2种尺寸的脉冲空化PDC钻头。在地层和钻井参数基本相同的情况下,与常规钻头相比,脉冲空化PDC钻头平均机械钻速提高30%以上。研究结果可为脉冲射流钻井提速提供理论依据。

In order to solve the existing problems of pulse jet drilling technology, such as pulse locations far from bottom hole, great loss of pulse effect along the path and application limitations in directional drilling assembly, a pulse cavitation PDC bit was designed. The inner cavity of the drill bit is designed as a pulse resonator cavity structure, where continuous jet is adjusted into pulse jet due to different shrink surfaces in each region of the cavity. The pulse jet is coupled with the bit cavitation nozzle to maximize the pulse effect on the bottom hole. The bottomhole flow fields and rock cleaning effect were studied and the results show that, the pulse generated by the pulse cavitation PDC bit could better turnover and migrate bottomhole cuttings from the bottom hole in time and reduce repeated cutting. The design of pulse location placed inside the bit closer to the bottom hole not only reduces the loss of pulse effects along the path, but also eliminates the need for additional joints or other special devices. The pulse cavitation PDC bit is applicable for all directional assemblies and improves the safety of drill strings. Two sizes of pulse cavitation PDC bit ( 215.9 and 311.2 mm) were developed. The field applications show that ROP was increased by more than 30% on average under the same formation and drilling conditions. The results could provide a theoretical basis for increasing ROP by pulse jet drilling.