SPE Drilling & Completion
Volume 25, Number 3, September 2010, pp. 391-408

SPE-111742-PA

A Design Strength Equation for Collapse of Expanded OCTG

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DOI  More information 10.2118/111742-PA http://dx.doi.org/10.2118/111742-PA

Citation

  • Klever, F.J. 2010. A Design Strength Equation for Collapse of Expanded OCTG. SPE Drill & Compl  25 (3): 391-408. SPE-111742-PA. doi: 10.2118/111742-PA.

Discipline Categories

  • 5.1 Design and Optimization
  • 5.1.1 Tubing and Casing Design

Keywords

  • expandable tubulars, collapse strength, test data, KT model, combined loads

Summary

Expandable tubulars provide exciting new opportunities for well design and construction. This technology has permitted access to hydrocarbons that could not be reached by conventional drilling techniques. Design tools similar to those available for conventional oil-country tubular goods (OCTG) are required to facilitate further dissemination and application of expandable tubulars. In particular, equations for performance properties of expanded pipe are needed.

This paper describes a method for developing an equation for the design collapse strength of any particular expandable-pipe product. It is based on the combination of collapse-test data and theoretical modeling, and its statistical approach is fully consistent with that used for conventional OCTG described in ISO/TR 10400:2007 (2007) or API TR 5C3 (2008).

On the basis of an example set of expanded L80 pipes, results are presented fitting the collapse data with an anisotropic version of the Klever and Tamano (KT) collapse equation (Klever and Tamano 2006) that has been calibrated recently to conventional OCTG. By adapting three parameters, the anisotropic KT model can also model the collapse strength of the expanded-pipe data over a range of pipe diameters, wall thicknesses, and expansion ratios. The historical API BULL 5C3 (1994) collapse formulas, even with adapted plastic-collapse parameters and reduced yield strength (YS), were found not suitable for matching this set of expanded-pipe collapse data.

Manufacturers may use the procedure described in this paper to develop design strength equations for specific expandable-pipe products, leading to product-specific sets of best-fit KT model parameters. The new equation takes account of the theoretical effect of internal pressure and axial load on collapse. The API SC5 RG ET Resource Group on expandable tubulars is incorporating the approach presented in this paper into the draft API RP 5-EX Recommended Practice.

© 2010. Society of Petroleum Engineers

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History

  • Original manuscript received: 14 May 2009
  • Meeting paper published: 5 March 2008
  • Revised manuscript received: 14 November 2009
  • Manuscript approved: 18 November 2009
  • Published online: 20 May 2010
  • Version of record: 13 September 2010