关键词: 黏滑振动, 吃入深度, 自适应限位齿, 结构设计

Abstract: 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.