Study on the Burst Failure Mechanism and Residual Strength of Casing With Compound Wear Based on Extended Finite Element Method

Based on the data of wear casing for ShunNan 501 well in Northwest oilfield and the stress-strain intrinsic relationship of P110 tubing, a two-dimensional mechanical model of casing with compound wear is established by using the nonlinear extended finite element method (XFEM) and the burst failure criterion of damage evolution with due consideration of wear type, angle between crescents, overlap depth of crescents, and wear depth caused by drill pipe body and tool joint. The accuracy and reliability of model are verified by the full-scale burst test data. The effects of wear types, angle between crescents, overlap depth of crescents, and wear depth on the internal pressure yield strength (IPYS), burst strength and failure behavior for casing with compound wear are analyzed, by which it is found that casing with compound wear exist stress interference and complex interaction between stress interference and stress concentration, and the burst failure mechanism of casing with compound wear is revealed. Based on the gray correlation analysis result of wear parameters, a prediction model of the residual strength for P110 casing with compound wear is established by 1stOpt software and universal global optimization (UGO) algorithm.