关键词: 瞬态响应 , 竖直井钻柱系统 , 转速突变 , 钻柱失效 , 有限元法

Abstract: Drilling is a complex transient process. Speed will reduce instantly when drillstring hits a hard rock suddenly and an accelerate process follows it until the speed accelerates to normal value. To observe the dynamic characteristics of drillstring in this case, using the finite element software "ANSYS" to analyze a constant speed process and accelerate processes of drillstring system in vertical well and gets the discipline of drillstring's vibration. The results show that after hitting hard rocks, the collision between drillstring and the borehole wall will happen for the hitting effect between rocks and bit, and the collision strength has a great relationship with acceleration time, if the acceleration time is short, the collision is slight and the force is small; if the acceleration time is long, the vibration will be exacerbated significantly, the collision is more serious and the force increases. In a word, the variable speed of drillstring exacerbates its vibration.

Key words: Transient response,    , Drillstring system of vertical well,    ,  Speed mutation,    ,  Drillstring failure,    ,  Finite element method