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Purpose <p>Addressing the current issue of over-simplification in the dynamics model of the drillstring system. The purpose of this paper is to study the dynamic response characteristics of drillstring, borehole wall, bit and rock coupling system under different drilling parameters.</p> Methods <p>In this work, a nonlinear coupling finite element mathematical model of the entire well section is established, incorporating the drillstring, cone bit, rock, and borehole wall during the air drilling process. A new boundary condition of hook load at the top and weight on bit at the bottom is adopted. Additionally, the discontinuous support model is introduced to establish the contact relationship between the tricone bit and the formation. To minimize low-frequency dissipation, we use NOCH-α method to solve dynamic equations of drillstring system.</p> Results <p>The analysis results show that the response of drill string in horizontal section is the most sensitive when drilling parameters change. To a certain extent, with the decrease of weight on bit(WOB) and rotational speed, the dynamic buckling amplitude of the drillstring decreases, the contact force and frequency between drillstring and borehole wall are reduced, the bit-bounce and stick–slip motion disappear gradually, and the vibration frequency and amplitude of the drilling system are lessened.</p> Conclusion <p>The results are consistent with the actual drilling data in the field. The coupling model of drill string system can provide theoretical reference for the optimization of drilling parameters and vibration control of drill string system.</p>

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Nonlinear Dynamics of Tricone Bit-Drillstring Coupling System in Deviated Wellhole with Air Circulating

  • 期刊论文

  • 发表日期：

    2025年1月6日

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  • Pan Fang,
  • Xiao Huang,
  • Yong Zhang,
  • Haibiao Wang,
  • Yancai Gao,
  • Huohai Yang

摘要

Purpose

Addressing the current issue of over-simplification in the dynamics model of the drillstring system. The purpose of this paper is to study the dynamic response characteristics of drillstring, borehole wall, bit and rock coupling system under different drilling parameters.

Methods

In this work, a nonlinear coupling finite element mathematical model of the entire well section is established, incorporating the drillstring, cone bit, rock, and borehole wall during the air drilling process. A new boundary condition of hook load at the top and weight on bit at the bottom is adopted. Additionally, the discontinuous support model is introduced to establish the contact relationship between the tricone bit and the formation. To minimize low-frequency dissipation, we use NOCH-α method to solve dynamic equations of drillstring system.

Results

The analysis results show that the response of drill string in horizontal section is the most sensitive when drilling parameters change. To a certain extent, with the decrease of weight on bit(WOB) and rotational speed, the dynamic buckling amplitude of the drillstring decreases, the contact force and frequency between drillstring and borehole wall are reduced, the bit-bounce and stick–slip motion disappear gradually, and the vibration frequency and amplitude of the drilling system are lessened.

Conclusion

The results are consistent with the actual drilling data in the field. The coupling model of drill string system can provide theoretical reference for the optimization of drilling parameters and vibration control of drill string system.