SPE Drilling & Completion
Volume 25, Number 4, December 2010, pp. 500-508

SPE-119748-PA

Case History: Successful Wellbore Strengthening Approach in a Depleted and Highly Unconsolidated Sand in Deepwater Gulf of Mexico

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DOI  More information 10.2118/119748-PA http://dx.doi.org/10.2118/119748-PA

Citation

  • Fett, D., Martin, F., Dardeau, C., Rignol, J., Benaissa, S., Adachi, J., and Pastor, J. 2010. Case History: Successful Wellbore Strengthening Approach in a Depleted and Highly Unconsolidated Sand in Deepwater Gulf of Mexico. SPE Drill & Compl  25 (4): 500-508. SPE-119748-PA. doi: 10.2118/119748-PA.

Discipline Categories

  • 1.4.2 Drilling Fluids, Handling, Processing and Treatment
  • 1.2.5 Materials Selection (Casing, Fluids, Cement)
  • 1.3.1 Wellbore Integrity/Geomechanics
  • 1.4.3 Downhole Operations (Casing, Cementing, Coring, Geosteering, Fishing)
  • 1.1.5 Risk Reduction

Keywords

  • wellbore strengthening, stress caging, depleted reservoirs, unconsolidated reservoirs, lost circulation prevention

Summary

In early 2008, Total E&P USA sidetracked the Mississippi Canyon 243 #A2 well on its "Matterhorn" tension-leg platform (TLP) in the deepwater Gulf of Mexico. A preproject geomechanics study identified that the mud-weight/fracture-pressure window in the depleted and highly unconsolidated "A" reservoir was very narrow, creating a strong potential for mud losses during drilling and cementing of the 7-in. liner. The risk of losses was a primary concern because the well would be frac packed, and if a competent cement column did not reach a sufficient height, the ability to fracture the reservoir would have been compromised. To mitigate this risk, the decision was made to drill through the depleted reservoir using a flat-rheology synthetic-based fluid, engineered with a high concentration of bridging particles to impart a strengthening effect on the formation.

The designer fluid allowed the reservoir to be drilled through successfully and the 7-in. liner to be run and cemented with full returns. Analysis of the frac-pack data showed that the formation-breakdown pressure was lower than the wellbore pressures experienced while drilling and cementing the liner, suggesting that the designer fluid improved the fracture resistance of the formation. The results imply that using such a designer fluid can have a strengthening effect on depleted/unconsolidated formations, in which some operators have had limited success applying wellbore-strengthening techniques.

The implication for the industry is that this technique can and should be considered on wells with challenges and risks similar to those of the Matterhorn A2 well. This paper will describe the approach taken in the laboratory for the fluid design, as well as operational practices to apply the treatment on location. A post-mortem analysis will compare formation-breakdown pressures taken from the fracturing operations to actual wellbore pressures experienced while drilling and cementing, to demonstrate that a strengthening effect was realized.

© 2010. Society of Petroleum Engineers

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History

  • Original manuscript received: 10 December 2008
  • Meeting paper published: 18 March 2009
  • Revised manuscript received: 23 July 2009
  • Manuscript approved: 28 October 2009
  • Published online: 2 September 2010
  • Version of record: 16 December 2010