钻井液对钻柱横向振动固有频率的影响

为了研究钻柱系统的振动模态以及动力学特性,利用动力学理论研究了钻柱内、外钻井液对钻柱横向振动固有频率的影响。引入附加质量系数,通过线性化假设,并进行Laplace变换,导出了钻井液排量、井眼直径与钻柱外径的比值与附加质量系数的关系。研究结果表明,钻井液的存在导致钻柱的固有频率与不考虑钻井液相比有较大的下降;钻柱内、外钻井液对钻柱横向振动固有频率的作用机理不同,其中环空内钻井液对钻柱横向振动固有频率的影响要远远大于人们的估计。

Influence of drilling fluid on natural frequency of drill string lateral vibration

In order to study the vibration modal and dynamic properties of drill string system, the influence of drilling fluid in and out of the drill string on natural frequency of drill string lateral vibration was studied based on the dynamic theory. By introducing the additional mass factor and linear hypothesis, the relation among the additional mass factor, drilling fluid displacement and the ratio between outer diameter of drill string and well diameter was obtained through Laplace transform. The results show that the natural frequency of drill string lateral vibration drops compared with inexistence of drilling fluid. The mechanism of drilling fluid in and out of the drill string for the natural frequency of drill string lateral vibration is different. The influence of drilling fluid in the annulus on natural frequency of drill string lateral vibration is larger than ordinary estimation results.