Assessment of Post-Expanded Mechanical Performance of Materials and Evaluation of Material Expandability Limit

AUTHOR/S: A. Bufalini, SPE, and R. Morana, Centro Sviluppo Materiali; P.I.Nice, Statoil ASA; and B. M. Bailey, Baker Hughes


The expandable tubular technology has seen an increased diffusion in the well construction process. It is accepted in well remediation activities, the consideration given to expandable technology as a primary option for well design is limited. Extreme expandable applications require very high expansion ratios, thus exceeding the elongation to failure of conventional casing materials; even specially selected casing materials are close to the limit of their deformation capability. Statoil decided to extend the scope of a previous research program on materials for expandable applications to include an initial investigation into defining a material’s expandability limit. A selected carbon steel grade was analyzed using specific experimental test methods and Finite Element Analysis (FEA), and employing previous results of other carbon steel grades and alloys. The experimental activities involved tensile tests on post-expanded material using optical systems for the strain measurement, a technique previously adopted for as received material. This method allowed the determination of the true stress-strain curve far beyond the range of standard methods. The test results showed the carbon steel grade investigated maintained a significant deformation capability even after large expansions. The FEA campaign analyzed the same materials using a 3D model. The results allowed for the determination of a maximum deformation limit for the materials allowing a successful expansion.

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