关键词: 钻柱力学, 有限元法, 摩擦力, 非线性, 结构分析, 套管柱

Abstract: A finite element model of the drillstring in thedirectional orhorizontal wellbores is presented.The total deformation of the drillstring is divided as deformation related to the axis ofthe wellbore and the initial deformation forced by a curved wellbore.Then the non-linearproblem of the drillstring is sirnplified. The force and deformation along the whole drillstringare computed in a horizontal well with this model. The hook load as well as the contact statebetween the dirllstring and well wall can be obtained. The non-linear analysis of BHAS aredone,their results are compared with the linear results. The results in a whole drillstring areconlpared with those computed in terrns of the length of BHA. Also, the frictional analysisbased on the static analysis of the drillstring is improved due to a consideration of the contactbetween the drillstring and well wall. First computation about the force and deformation ofthe whole drillstring is d0ne. These examples show that the conclusion is reasonable. A newmethod is provided for mechanical analysis of the whole drillstring or BHA. The method pre-sented in the paper is adaptable to the analysis of casing strings also.

Key words: drillstring mechanic, finite element method, friction, non-linear, structure analysis, casing string