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<p>During the process of rotary drilling, severe lateral vibrations, known as whirling, will reduce the rate of penetration (ROP) and increasing drilling costs. Although it has been researched for several decades, the whirling pattern is still not clear. The prerequisite for whirl motion is lateral displacement. This paper identifies compressive buckling, mass eccentricity, and structural eccentricity as the key factors inducing drill string lateral displacement, and systematically investigates its whirling behavior using a dynamics model developed using the lumped mass method (LMM). The research findings indicate that solely due to compressive buckling, it can only enter a state of backward whirl. Under the influence of mass eccentricity alone, when the eccentricity is small, the drill string does not contact the wellbore wall. When the mass eccentricity exceeds a certain threshold, the entire section of the drill string will move along the wellbore wall in a forward whirl. Theoretical analysis confirms the plausibility of this phenomenon, demonstrating that gravity cannot mitigate mass-eccentricity-induced lateral displacement, with its absence at drilling sites attributable to the wider wellbore wall spacing in upper sections. Structural eccentricity also results in the drill string only being able to generate forward whirl and, together with mass eccentricity, constitutes the two essential factors inducing forward whirling in drill strings. The results under the combined influence of the three factors show that, in addition to the widely recognized forward whirl, backward whirl, and irregular motion, there indeed exists a non-revolutionary motion, a state of whirl that was proposed by scholars long ago. The wear of the drill string can alter the mass eccentricity, and the elastoplastic characteristics of the drill string material along with prolonged compressive buckling can change the structural eccentricity. Therefore, even if drilling parameters remain unchanged, variations in these two parameters can lead to complex and variable whirl states of the drill string. This is one of the significant reasons why it is currently difficult to predict the whirl state of the drill string in the field.</p>

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The influencing factors and new insights of drill string whirl in vertical wells

  • 期刊论文

  • 发表日期：

    2025年6月27日

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  • Bin Huang,
  • Hongjian Ni,
  • Heng Zhang,
  • Wei Li,
  • Yan Jin,
  • Yunhu Lu

摘要

During the process of rotary drilling, severe lateral vibrations, known as whirling, will reduce the rate of penetration (ROP) and increasing drilling costs. Although it has been researched for several decades, the whirling pattern is still not clear. The prerequisite for whirl motion is lateral displacement. This paper identifies compressive buckling, mass eccentricity, and structural eccentricity as the key factors inducing drill string lateral displacement, and systematically investigates its whirling behavior using a dynamics model developed using the lumped mass method (LMM). The research findings indicate that solely due to compressive buckling, it can only enter a state of backward whirl. Under the influence of mass eccentricity alone, when the eccentricity is small, the drill string does not contact the wellbore wall. When the mass eccentricity exceeds a certain threshold, the entire section of the drill string will move along the wellbore wall in a forward whirl. Theoretical analysis confirms the plausibility of this phenomenon, demonstrating that gravity cannot mitigate mass-eccentricity-induced lateral displacement, with its absence at drilling sites attributable to the wider wellbore wall spacing in upper sections. Structural eccentricity also results in the drill string only being able to generate forward whirl and, together with mass eccentricity, constitutes the two essential factors inducing forward whirling in drill strings. The results under the combined influence of the three factors show that, in addition to the widely recognized forward whirl, backward whirl, and irregular motion, there indeed exists a non-revolutionary motion, a state of whirl that was proposed by scholars long ago. The wear of the drill string can alter the mass eccentricity, and the elastoplastic characteristics of the drill string material along with prolonged compressive buckling can change the structural eccentricity. Therefore, even if drilling parameters remain unchanged, variations in these two parameters can lead to complex and variable whirl states of the drill string. This is one of the significant reasons why it is currently difficult to predict the whirl state of the drill string in the field.