Collapse Prediction Methodology for the Solid Expandable Tubular

Abstract

This paper summarizes an experimental and numerical study aimed at understanding the collapse resistance of expandable tubulars (EXP-T), both before and after expansion, and at constructing a prediction method for post-expanded collapse. Post-expanded collapse resistance is one of the important properties for EXP-T, and the high-collapse EXP-T is necessary for the realization of expandable tubular monobore wells. Thus, a reliable prediction technique can be useful for casing-design utilizing EXP-T. However, the current collapse formulas widely used are not applicable to post-expanded pipes.To solve this subject, firstly, full-scale expansion and collapse tests were performed to compare collapse resistance between two materials. Secondly, two prediction methods were validated for post-expanded collapse: finite element analyses (FEA) and the statistic formula used in conventional OCTG.The test results demonstrated that post-expanded collapse resistance is significantly degraded by the increase in the diameter-to-thickness ratio. There was a large difference in the reduction ratio of the collapse between the conventional and trial material, and the FEA model is capable of evaluating the precise collapse strength of post-expanded pipes by modeling the collapse governing factors. It was also clear that the distribution of residual stress after expansion is opposite to conventional OCTG, although the residual stress deteriorates the collapse resistance after expansion. Moreover, by modifying the definition of the mechanical property of the pipe, the collapse prediction formula is capable of accurately calculating the collapse pressure after expansion. This result is caused by the difference in the shape of stress-strain (S-S) curves between conventional OCTG and post-expanded pipes.We expect that this research work will contribute to improving our understanding of EXP-T collapse, and will help form the technical basis for the reliability of EXP-T casing design.

Dynamic Analysis of Solid Expandable Tubular and Its Applications in Tahe Oilfield

“…From Eqs. (19) and (20), it can be concluded that at time t n + t, every DOF of displacement can meet one autonomous equation, which contains the value of DOF of displacement in time t n and time t n − t, and thus, the matrix factorization is unnecessary.…”

“…Al-Abri [18] conducted a mechanical analysis and load calculation study for an expandable casing based on the elastic-plastic mechanics, but the stress-hardening effect of the casing material in the plastic stage and the impact of curved casing on the axial stress increment within the transition from the expansion section to the sizing section was ignored. Jun et al [19] and Qiang et al [20] aimed at understanding the collapse resistance both before and after expansion of SET by summarizing the experimental and theoretical study.…”