基于应力分析的钻具设计方法优化

钻具钻进过程中不断振动，其产生的交变应力促使钻具发生疲劳失效。钻具组合设计时多是考虑轴向应力对钻具的影响，很少考虑到振动的影响，考虑因素单一。为提高钻具钻进过程的安全性，基于钻柱所受轴向应力，考虑钻柱振动时所受动态应力，结合疲劳失效原理，建立了一种应力安全分析模型，并通过室内试验验证模型的合理性，进而分析钻柱整体在不同钻进条件下的安全系数和存在的危险位置，总结提出钻具组合优化方法。结果表明：转速对钻具的安全系数影响较大，钻压的影响程度较小；除了钻具井口位置，加重钻杆底部、钻铤底部均存在疲劳失效的可能；钻具优化方法可以提高钻具整体安全性。本文从应力方向角度分析了钻具的安全情况，提出了优化方法，为以后的钻具设计提供了参考。

Optimization of Drilling Tool Design Method Based on Stress Analysis

The drill string vibrates continuously in the process of drilling, and the alternating stress causes the fatigue failure of the drilling tool. In the design of drilling tool assemblies, people mainly considers the influence of axial stress on drill string, without considering the influence of vibration, and the factors considered is simple. To improve the safety of the drilling process, besides the axial stress on the drill string, the fatigue failure and the dynamic stress produced by the vibration of the drill string are taken into consideration. Then a stress and safety analysis model is established. The safety factor and dangerous position of the drill string under different drilling conditions are analyzed. The rationality of the model is verified by indoor laboratory tests. Finally, the optimization method of drilling tool assembly is summarized and put forward. The results show that the rotating speed has a great influence on the safety factor, and the influence of the weight on bit (WOB) is small. In addition to the wellhead position of the drilling tool, fatigue failure may occur at the bottom of the weighted drill pipe and the bottom of the drill collar. The proposed optimization method can improve the overall safety of drilling tool. In this paper, the safety of drilling tool is analyzed from the perspective of stress direction, and the optimization method is put forward, which provides a reference for drilling tool design in the future.