偏磨套管破裂强度三维弹塑性有限元分析

为了更真实地模拟套管在内压下的破裂过程及影响因素，基于弹塑性大变形理论，建立套管三维有限元模型，对偏磨套管的破裂问题进行了研究。结合实验数据，提出了新的判断套管破裂的强度准则，给出了“月牙形”模型中偏磨率和“偏心筒”模型中偏心率的关系，并讨论了偏磨半径和偏磨率对偏磨套管破裂强度的影响。结果显示，套管内壁应力达到极限强度作为套管破裂的强度准则较为准确；偏磨半径对套管破裂强度影响较小；破裂压力随偏磨率的增加近似呈线性下降。研究结果可为套管柱设计提供理论支持。

Collapse strength analysis of eccentric wear casing based on a three-dimensional elastic-plastic finite element method

In order to simulate the process of casing collapse and analyze the influence factor more realistically, a three-dimensional finite element model for casing was established and the eccentric wear casing collapse problem under internal pressure was studied, based on elastic-plastic large deformation theory. According to the experimental data, a new strength criterion to judge casing collapse was proposed, and the influence of partial wear radius on collapse strength was analyzed. A relationship between the eccentric wear rate in the “crescent-shaped” model and the eccentricity in “eccentric cylinder” model was given and the influence of the eccentric wear radius and the eccentric wear rate on collapse strength was discussed. Results showed that, the ultimate stress on casing inner wall was relatively accurate as the collapse strength criterion. Eccentric wear radius had little impact on casing collapse strength. Besides, the collapse pressure almost linearly decreased with the increase of the eccentric wear rate. This paper provides a theoretical support for casing string design.