Evaluating the Expandability and Collapse Resistance of Expandable Tubulars

Abstract

Expandable tubular technology is an effective method for saving on the costs of well drilling and completion. There are many applications for casing repair and slim hole casing design. The most essential performances of expandable tubular (EXP-T) are the expandability and collapse resistance, which are affected by not only the expanded pipe properties, but also the axial restraint caused by sticking pipe in well.This paper discusses the geometrical and material factors governing pipe expandability, the effect of axial restraint during the expansion, and the collapse resistance of the expanded pipe. Two types of pipe were evaluated using pipe expander equipped with a function of the axial restraint. FEA for pipe expansion considering the pipe geometries and the mechanical property were also carried out for solving the fracture mechanism and deriving the design diagram of EXP-T. In addition, the full-scale collapse tests were performed for evaluating the collapse resistance of the expanded pipes and verifying the prediction using the conventional formulas.These results reveal the relevant combination of the pipe geometries and the material properties for preventing the expansion failure. A potential to improve the collapse resistance of the pipe expanded under the axial restraint is drawn.

Collapse Prediction Methodology for the Solid Expandable Tubular

“…However, the conventional collapse formulas for OCTG and linepipes have not been validated for the expanded pipes, since the mechanical properties and geometries of EXP-T are greatly changed by pipe expansion. Few attempts have been made to show the collapse prediction formula 5 or to measure the collapse resistance of post-expanded pipes [6][7][8][9][10] .…”