基于黏滑振动机理研究的钻头自适应限位齿结构设计

乍得某盆地基岩潜山地层主要由花岗岩构成，岩石研磨性强、可钻性差，使钻头黏滑振动现象成为制约安全钻井与高效开发的主要不利因素之一，亟待开展黏滑振动机理与解决对策研究。本文采用有限元模拟与室内实验等研究手段，以钻头单齿微观动态破岩过程为切入点，模拟分析了钻压、吃入深度对钻齿切削效率的影响，揭示了钻齿吃入深度过大影响钻具扭转、塑性—脆性破碎形式转变、岩石破碎动态平衡打破的黏滑振动发生机理，并估算得到不同岩性地层的吃入深度推荐范围。据此创新设计了自适应限位齿控制单元，通过数值模拟方法对其结构参数进行优化改进。加工样机后进行结构力学运动性能的室内台架压载测试，测试发现，加载时限位块能够有效抵抗模拟钻压而缓慢压入，卸载后又能相对快速地伸出本体，基本实现本结构的设计目的，即自适应地控制钻头切削齿有效吃深，降低黏滑振动发生概率，保护钻头钻柱，减少起下钻频次与降低失稳断裂风险，为钻井提速增效与高效开发深部复杂地层资源提供技术支撑。

Design of Auto-response DOC Controller on the Basis of Mechanism Research of Stick-slip Vibration

Stick-slip vibration has been one of the major problems during drilling operations in a basin, Chad. Hardness and brittleness of gneiss granite, the key lithology in basement reservoir has become the main cause of stick-slip vibration and further premature failure of drill bits and string, posing a serious threat to safe and cost-saving drilling and oilfield development. Hence, it is urgent to carry out the mechanism study of stick-slip vibration and structure design to manage the problem. Numerical simulations and lab experiments were run in this research to describe the micro dynamic rock cutting process, establishing the relation between depth of cut (DOC) and cutting performance or bit rotation. Lithological alternation and excessive DOCs are revealed as the root cause of stick-slip vibration, and furthermore, optimized DOCs for different rock layers are recommended. A novel design of auto-response DOC controller is proposed based on it to manage DOC and bit rotation in real time, followed by the modifications of structural features and parameters via numerical simulations. The controller was then machined and tested on mechanics and hydrodynamics. Results show that it has met the standards of satisfactory motion as it slowly retracts into the body by resisting the load and quickly extend outwards. The auto-response DOC controller has provided a sound theoretical basis for anti-stick-slip PDC bit and has profound application potential in increasing ROP and efficiently developing the ultra-deep and unconventional reservoirs.