钻柱动态疲劳失效风险实时监测技术研究

Research on Risk Monitoring Technology for Dynamic Fatigue Failure of Drill String

摘要: 深井超深井钻进过程中，钻柱受力复杂，容易发生断裂情况，但目前现场缺少钻柱失效实时监测与风险预警技术。基于钻柱力学分析，考虑了井眼轨迹、钻柱接头、钻柱涡动等影响，建立了钻柱疲劳损伤计算模型，分析了相关影响规律，形成了钻柱疲劳失效风险实时监测软件。结果表明，即使钻柱承受的拉载、扭载和综合应力未超过其各自极限值，也可发生低应力下的疲劳破坏。强化钻进参数作业工况下，钻柱旋转通过高狗腿度井段时更易产生疲劳损伤。下部钻具压缩段的疲劳损伤在无屈曲时影响小，有屈曲时影响较大。转速对钻柱疲劳影响很大，高转速情况下钻柱受到频率更快的交变载荷，加速其疲劳损伤。钻柱疲劳失效风险监测软件可以实时监测钻柱动态失效情况，可以为钻柱安全作业提供技术保障。

Abstract: During the drilling process of deep and ultra-deep wells, the drill string is subjected to complex forces and is prone to fracture. However, there is currently a lack of real-time monitoring and risk early warning technologies for drill string failure on site. Based on drill string mechanics analysis, and considering the influences of borehole trajectory, drill string joints, and drill string whirling, a calculation model for drill string cumulative fatigue damage was established. Relevant influencing patterns were analyzed, leading to the development of real-time monitoring software for drill string fatigue failure risk. The results indicate that fatigue failure under low stress can occur even when the tensile load, torsional load, and comprehensive stress on the drill string do not exceed their respective limit values. Under enhanced drilling parameters, the drill string is more susceptible to fatigue damage when rotating through high-dogleg sections. The fatigue damage in the compressed section of the bottom hole assembly (BHA) has a minor impact when no buckling occurs, but a significant impact when buckling is present. The rotational speed (RPM) greatly affects drill string fatigue; at high RPM, the drill string experiences faster-frequency alternating loads, which accelerates its fatigue damage. The drill string fatigue risk monitoring software can monitor the dynamic failure status of the drill string in real-time, providing technical assurance for the safe operation of the drill string.