中短半径水平井弯曲井段套管受力分析

套管柱在高井眼曲率的水平井弯曲井段将产生较大弯曲应力和较大的径向变形，有可能导致强度破坏和变形失稳。为了研究套管在弯曲载荷作用下的应力分布及变形情况，采用三维实体单元，运用有限元方法建立了中短半径水平井弯曲井段套管的计算模型，分析了三种不同外径尺寸的套管在一定围压和不同弯曲载荷作用下的最大径向变形量和最大等效应力值，并分析其随井眼曲率的变化规律。计算表明，井眼曲率增大，弯曲井段套管的径向变形和应力也随之增大；同一井眼曲率下，外径较大的套管，径向变形和应力也较大。通过研究，对高井眼曲率下中短半径水平井弯曲井段套管柱强度设计提供了理论依据。

Force Analysis of Casing in the Curved Portion of Medium/Short Radius Horizontal Wells

A big bending stress and radial transfiguration of the casing string occur in the curved portion of horizontal well with large borehole curvature, which might result in strength breakage and destabilitzing. In order to study the stress distribution of casing and its transfiguration under bending load, this paper establishes the calculation model of the casing in the curved portion of medium/short radius horizontal wells by using FEM method and solid element in three dimensions, analyses the largest radial transfiguration amount and the largest equivalent stress of three external diameter casing under definite confining pressure and different loads. Calculation results show that the radial transfiguration amount and the equivalent stress increase with the increase of borehole curvature, and those of the casing with bigger external diameter are bigger under the same borehole curvature. The study of this paper provides theoretical basis for the strength design of casing string in the curved portion of horizontal well with large borehole curvature