Modal Analysis Of Drill Stem Vibration

The vibration of drill stems in practical engineering is inevitable. The vibration includes longitudinal vibration, transverse vibration, torsion vibration as well as their coupling. Strong sympathetic vibration of drill stems could lead to severe failure of drilling. It will increases difficulty and risk on drilling, even brings huge economic loss along.Theoretical analyses of three kinds of vibrations are discussed separately in this paper. By making a summary for three kinds of vibrations, mechanical modal is established, vibration equation is deduced and the sympathetic rules of drill stem are derived. This paper emphasizes on simulation of finite element method parametrically modal based on software ANSYS for drill stems. This modal has strong practicability and currency, which will improve the efficiency of analyses and researches greatly and will establish the better foundation for further investigation with SHENG DEEP No.7 well in Taching oilfield as an example. During the modeling, pressure and flotage power of the well are considered. Comparing with existing finite element model, the simulation level is improved. The analysis result can provides a valuable reference to escaping while drilling. The analysis result can also offer the computational method to confirm the critical rotating speed for different kinds of drill bits. In addition, the calculation result indicates frequencies of the two kinds of vibrations, which is important direction to the problems of sympathetic failure of a drill stems, and location of vibration reducer. Compared with the analysis results, longitudinal vibration and transverse vibration have the same domain. The nearly same nodes are on maximal displacements of each step. The failure of a drill stem most likely occurs near these nodes. So this paper has the reference meaning to the drill stems' design, manufacture and engineering application.