Fatigue failure analysis based on coupling vibration of drill string in ultra-deep wells Online publication date: Thu, 01-Aug-2024
by Guojie Cui; Hongshan Zhao; Runfeng Cai; Donghong Guo; Sheng Zhong; Wenchang Wang
International Journal of Oil, Gas and Coal Technology (IJOGCT), Vol. 36, No. 2, 2024
Abstract: Fatigue failure of drill string occurs frequently in deep wells. However, the commonly used fatigue ratio is difficult to evaluate drill string fatigue safety accurately. In this paper, considering the characteristics of super slenderness ratio of drill string and collision with the wellbore wall, the coupling vibration of drill string is studied, and the vortex characteristics and dynamic stress of the drill string are calculated more accurately. On this basis, combined with the calculation method of fatigue coefficient under asymmetric variable stress amplitude, the strength criterion of fatigue failure of drill string under dynamic condition is established. The results show that this method can better understand the working state of the drill string in the wellbore and predict the risk position of fatigue failure of whole drill string more accurately in vertical wells. [Received: March 28, 2023; Accepted: February 13, 2024]
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