In the process of drilling direction wells, drill string vibration includes longitudinal vibration, transverse vibration and torsional vibration, which coupled vibration is more major factors leading to the force on drill string. In the 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, result in economic loss to the drilling operation. In this paper, the regularity of coupled vibration was analyzed by using finite element method. Firstly, according to the characteristics of direction wells, a whole-well drill string model was established. The regular distribution of coupled resonant frequency was obtained by computer analysis. It is very significant that the study on this issue can be used to direct drilling operation and reduce accidents such as bit bounce, drill string failure and so on.
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