Drilling a wellbore can result in several types of vibration that lead to inefficient drilling and premature failure of drill string components. These vibrations are subdivided based on their operating direction into lateral, torsional, and axial vibrations. Especially in hard and dense formations, high-frequency torsional oscillations are found in the bottom-hole assembly (BHA). These critical vibrations are induced by a self-excitation mechanism caused by the bit–rock interaction. Self-excitation mechanisms are regenerative effects, mode coupling, or a velocity-dependent torque characteristic at the drill bit. To increase drilling performance and reduce tool failure due to high-frequency torsional oscillations, the critical vibration amplitudes localized at the bottom-hole assembly need to be minimized. Increasing the damping of self-excited systems to affect the energy output during vibration is a common approach to mitigate self-excited vibrations. In drilling systems, the achievable damping is naturally limited by the small installation space due to the drilled borehole diameter. Therefore, alternative methods to influence vibrations are necessary. Applying parametric excitation in self-excited systems can result in a parametric anti-resonance and therefore in an energy transfer within different modes of the structure. This allows, among other benefits, improved utilization of the structural damping. In this article, the influence of additional stiffness–based parametric excitation on self-excited torsional vibration in downhole drilling systems is investigated. For this purpose, a finite element model of a drill string is reduced using the component mode synthesis and analyzed with the goal to mitigate torsional vibrations. The multiple degree of freedom drill string model is investigated regarding the additional energy transfer due to the parametric excitation. Robustness of various parameters, especially with regard to the positioning within the bottom-hole assembly, is analyzed and discussed. Additionally, the problem of multiple unstable self-excited modes due to the nonlinear velocity-dependent torque characteristic in drilling systems is addressed.

钻探井眼会导致多种类型的振动，从而导致钻探效率低下和钻柱组件过早失效。这些振动根据其运行方向细分为横向、扭转和轴向振动。特别是在坚硬致密的地层中，在井底组合 (BHA) 中发现了高频扭转振荡。这些临界振动是由钻头-岩石相互作用引起的自激机制引起的。自激机制是再生效应、模式耦合或钻头处与速度相关的扭矩特性。为了提高钻井性能并减少由于高频扭转振荡引起的工具故障，需要最小化井底组合处的临界振动幅度。增加自激系统的阻尼以影响振动期间的能量输出是减轻自激振动的常用方法。在钻井系统中，由于钻孔直径，可实现的阻尼自然受到安装空间小的限制。因此，需要替代方法来影响振动。在自激系统中应用参数激励会导致参数反共振，从而导致结构不同模式内的能量转移。除其他好处外，这允许改进结构阻尼的利用。在本文中，研究了基于附加刚度的参数激励对井下钻井系统中自激扭转振动的影响。以此目的，钻柱的有限元模型使用组件模式合成进行了简化，并以减轻扭转振动为目标进行了分析。研究了多自由度钻柱模型关于参数激励引起的额外能量传递。分析和讨论了各种参数的稳健性，特别是与井底组合内的定位有关的参数。此外，解决了由于钻井系统中非线性速度相关扭矩特性而导致的多种不稳定自激模式的问题。特别是关于井底组合内的定位，进行了分析和讨论。此外，解决了由于钻井系统中非线性速度相关扭矩特性而导致的多种不稳定自激模式的问题。特别是关于井底组合内的定位，进行了分析和讨论。此外，解决了由于钻井系统中非线性速度相关扭矩特性而导致的多种不稳定自激模式的问题。