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<p>During the drilling process, the drill string system is highly susceptible to stick-slip, whirl, and jump vibrations, which can lead to fatigue fracture failure—especially in ultra-high-pressure, high-temperature (HPHT) oil and gas wells. To address this, an axial-lateral-torsional (ALT) coupled nonlinear vibration model of the drill string system in ultra-HPHT deep wells is established. A nonlinear vibration simulation device for the drill string is then developed, incorporating the coupling effects of drilling tools across the entire wellbore. Theoretical calculations are compared with simulation test results to validate the accuracy of the ALT model. Using this model, the influence of key operational parameters—including weight on bit (WOB), rotary speed, torque excitation, and sine wave moment amplitude—on drill string failure mechanisms is investigated. The findings reveal the following: As WOB increases, the fatigue life of the drill string initially rises before declining, indicating an optimal WOB value for maximizing service life. The proposed analytical method can determine this optimal WOB, providing practical guidance for field operations. The drill string’s fatigue life exhibits a three-stage variation with increasing rotational speed: first increasing, then decreasing, and finally increasing again. An optimal speed configuration exists that significantly enhances drill string longevity. Field operations can leverage this analysis method to select the best rotational speed based on well conditions and structural design. symmetrical excitation torque with a load amplitude of 2400 N·m is recommended, as it effectively improves drilling efficiency while maintaining sufficient fatigue life of the drill string. This study provides a theoretical and experimental foundation for optimizing drilling parameters in HPHT environments, enhancing both operational safety and drill string durability.</p>

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Coupled axial-lateral-torsional vibration modeling and fatigue failure mechanisms of drill strings in ultra-high temperature/pressure wells

  • 期刊论文

  • 发表日期：

    2026年4月9日

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  • Xiaoqiang Guo,
  • Yilin Tong,
  • Junlin Lv,
  • Kelun Yang

摘要

During the drilling process, the drill string system is highly susceptible to stick-slip, whirl, and jump vibrations, which can lead to fatigue fracture failure—especially in ultra-high-pressure, high-temperature (HPHT) oil and gas wells. To address this, an axial-lateral-torsional (ALT) coupled nonlinear vibration model of the drill string system in ultra-HPHT deep wells is established. A nonlinear vibration simulation device for the drill string is then developed, incorporating the coupling effects of drilling tools across the entire wellbore. Theoretical calculations are compared with simulation test results to validate the accuracy of the ALT model. Using this model, the influence of key operational parameters—including weight on bit (WOB), rotary speed, torque excitation, and sine wave moment amplitude—on drill string failure mechanisms is investigated. The findings reveal the following: As WOB increases, the fatigue life of the drill string initially rises before declining, indicating an optimal WOB value for maximizing service life. The proposed analytical method can determine this optimal WOB, providing practical guidance for field operations. The drill string’s fatigue life exhibits a three-stage variation with increasing rotational speed: first increasing, then decreasing, and finally increasing again. An optimal speed configuration exists that significantly enhances drill string longevity. Field operations can leverage this analysis method to select the best rotational speed based on well conditions and structural design. symmetrical excitation torque with a load amplitude of 2400 N·m is recommended, as it effectively improves drilling efficiency while maintaining sufficient fatigue life of the drill string. This study provides a theoretical and experimental foundation for optimizing drilling parameters in HPHT environments, enhancing both operational safety and drill string durability.