井眼间隙对下部钻具组合横向振动的影响

Effects of wellbore gap on transverse vibrations of bottom hole assemblies

将下部钻具组合看成钻头处铰支的细长梁,同时考虑井眼间隙与钻压波动对下部钻具组合的作用,应用有限单元法建立下部钻具组合的动力学基本方程,采用数值模拟的方法得到下部钻具组合动态响应,并进行频谱分析。对不同井眼间隙时的下部钻具组合的横向振动数值模拟结果表明,振动幅值随稳定器与井壁之间间隙增大而增大。并且可能存在稳定器与井壁之间的间隙的临界值,当达到该临界值时,钻具组合的振动剧烈。

In this paper the bottom hole assembly is modeled as a slender beam with a simplysupported end at bit. The effects of both the fluctuation of WOB and interaction between drill string and well wall on bottom hole assembly are involved in this model. Dynamic equations of bottom hole assembly are set up with finite element assembly. The dynamic responses of bottom hole assembly are solved by numerical simulation method and its frequency spectrums are analyzed. Numerical results in the different wellbore gaps show that amplitude of transverse vibration is increased with gap between drill string and well wall. There is a threshold of gap between drill string and well wall. When the threshold is exceeded transverse vibration becomes more violent. 