定向井轴向振动有限元分析

在定向井钻井施工中钻柱受力是很复杂的.仅钻柱振动就存在轴向振动、横向振动和扭转振动,其中钻柱轴向振动是导致钻柱失效的主要因素之一,因此需要进一步对定向井轴向振动进行研究.利用有限元方法分析了钻柱轴向振动规律.首先根据定向井特点建立全井钻柱模型,然后以钻柱单元为研究对象,建立了全井钻柱轴向振动的力学模型,采用线性代数方法,通过计算机分析获得了钻柱轴向振动的共振频率分布规律.钻柱轴向共振,其共振频率取决于钻柱的材料性能及形态特性,与钻柱的长度关系不大.在达到轴向共振状态时,钻柱与井壁激烈地碰撞,使钻柱短时间内产生严重破坏,同时还会造成井塌事件,给钻井施工带来经济损失.该问题的研究对指导钻井施工,减少跳钻、避免钻柱失效等情况有很大意义.

Finite Element Analysis of Longitudinal Vibration of Direction Well

The force on the drill string is very complex in the process of drilling direction wells. A merely drill string vibration includes longitudinal vibration, transverse vibration and torsional vibration, of which longitudinal vibration is one of the major factors leading to drill string failure. Therefore, the longitudinal vibration of direction wells is needed to further study. In this paper, the regularity of longitudinal vibration was analyzed by using finite element method. Firstly, according to the characteristics of direction wells, a whole-well drill string model was established, then with the drill string module as an object of study, a whole-well drill string mechanical model of longitudinal vibration was established. Through analysis of the computer by means of linear algebra, the regular distribution of longitudinal vibration resonant frequency of direction wells was obtained. The resonant frequency of drill string longitudinal vibration depends upon material properties of drill string and morphological characteristics, but has little to do with the length of the drill string. In the longitudinal resonance state, drill string comes into intense collision with the wall, which will cause serious damage on drill string in a short time. At the same time even give rise to borehole collapse, result in economic loss to the drilling operation. It is very significant that the study of this issue can be used to direct drilling operation and reduce accidents such as bit bounce, drill string failure and so on.