SPE Drilling & Completion
Volume 27, Number 4, December 2012, pp. 473-485

SPE-139766-PA

Casing Burst Stresses in Particulate-Filled Annuli: Where Is the Cement?

View full textPDF ( 1,054 KB )

DOI  More information 10.2118/139766-PA http://dx.doi.org/10.2118/139766-PA

Citation

  • Kalil, I.A. and McSpadden, A.R. 2012. Casing Burst Stresses in Particulate-Filled Annuli: Where Is the Cement? SPE Drill & Compl.  27 (4): 473-485. SPE-139766-PA. http://dx.doi.org/10.2118/139766-PA.

Summary

For burst design, engineers routinely assume that the casing annular space is filled by a fluid equivalent. This assumption ignores mechanical resistance provided by solid cement. Some studies addressed this shortcoming by modeling the cement sheath as a solid with elastic failure criteria. Prior work used cement elastic modulus and Poisson's ratio to classify cement as "ductile" (soft) or "brittle" (hard). In the current study, numerical results from finite-element analysis (FEA) indicate that casing burst resistance is increased by the presence of the cement sheath. This study focuses solely on improvement offered by the cement sheath to casing burst resistance and ignores consequences of cement failure on overallwell integrity. Comparisons are provided for casing burst resistance, assuming various backup profiles. These include fluid hydrostatics, solid cement matrix (both elastic and plastic response), and cement as "loose" particles. The fluid hydrostatics include mud weight in hole, cement-slurry density, mixed-water density; normal pressure (saltwater column), and actual pore pressure. Calculations show that these fluid profiles are conservative when used as burst-resistance backup. Original cement-slurry density is least conservative. Because well designers are familiar with fluid profile backup assumptions in casing burst design, recommendations are provided to approximate cement behavior as particles with a fluid profile. This allows ease of calculation and is consistent with current practice. Guidelines are provided to explicitly calculate the enhanced casing burst resistance caused by the particulate cement.

© 2012. Society of Petroleum Engineers

View full textPDF ( 1,054 KB )

History

  • Original manuscript received: 23 June 2011
  • Meeting paper published: 1 March 2011
  • Revised manuscript received: 27 March 2012
  • Manuscript approved: 10 September 2012
  • Published online: 29 November 2012
  • Version of record: 11 December 2012