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.