An Experimental and Numerical Approach to the Prediction of Expandability and Collapse Resistance for Solid Expandable Tubulars

摘要

This paper describes the material and form factors that control pipe expandability, the influence of axial restraint during expansion on pipe expandability, and the post-expansion collapse resistance of solid expandable tubulars. Of the various properties required for the pipe used in an expandable-tubular system, the most important are pipe expandability and collapse resistance. Therefore, clarification of the factors that control pipe expandability and development of a reliable technique to predict pipe-collapse resistance should be useful for the design of casings that use expandable tubulars. These tasks were tackled as follows. First, two types of pipe were evaluated by use of a pipe expander that is capable of imposing an axial restraint on the pipe. Next, to prepare a design diagram for pipe expandability, a numerical analysis was carried out by use of the finite-element method (FEM). In addition, a full-scale collapse test was carried out to compare the collapse resistance of the two types of pipe. Then, the validity of two techniques for predicting the collapse resistance of expanded pipe-FEM model and conventional formula-was determined. The results of the research revealed the appropriate combination of pipe form and mechanical properties that can prevent pipe from breaking because of expansion. In addition, the expandability of the pipe decreases markedly under an axial restraint imposed on the pipe during expansion. In addition, it is possible to accurately predict the collapse resistance of pipe after expansion by use of an FEM simulation. Furthermore, by modifying the definitions for pipe mechanical properties, it was also discovered that the collapse-prediction formula can be used to accurately predict the collapse resistance of pipe after expansion. The study results will deepen the understanding of the expandability and collapse of expandable tubular pipes and provide basic data for improving the reliability of casing designs that call for expandable tubulars.