This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 29943, “Seal Qualification and Single-Trip Lockdown Sleeve Reduce Risk Through Innovative and Advanced Technology,” by Scott Patrick Ellisor, Rodrigo Albani Queiroz, and Carlos Eduardo Martins Gaban, Dril-Quip, et al., prepared for the 2019 Offshore Technology Conference Brasil, Rio de Janeiro, 29-31 October. The paper has not been peer reviewed. Copyright 2019 Offshore Technology Conference. Reproduced by permission.

Traditionally, a wellhead system requires a drilling lockdown sleeve (LDS) during drilling operations to ensure that the seal assembly is rigid and prevents dynamic movement. By eliminating the LDS, however, the operator will save multiple trips into the well. Because of a seal-assembly design outlined in the complete paper, development of a single-trip LDS was possible for wellhead systems requiring extremely high lockdown requirements, allowing the user to save trips required by legacy designs.

New Subsea Challenges

In high-pressure/high-temperature subsea wells, annular pressure buildup, caused by thermal expansion of fluid, endangers well integrity. This phenomenon is caused by the increase of pressure during the production phase, temperature differential during the drilling phase, and fluid parameters. This type of annuli pressure buildup causes uplift as high as 3,200,000 lbf. The number of times the system needs to be shut down could be as many as eight per year for a 25-year well life; the life of the field during the production phase, therefore, could see as many as 200 total cycles.

Saving Rig Time by Implementing New Technologies

The technologies presented in the complete paper are the single-trip LDS and the dynamic casing hanger seal assembly. The single-trip LDS is used if an extremely high lockdown capacity is required. When this LDS is used, the need to run a lead impression tool (LIT) before running the lockdown sleeve is eliminated. Thus, an extra tool on the rig floor is eliminated, as well as a trip into the well. By eliminating the LIT run, between 5 and 10 hours could be saved, depending on water depth. Similar to the way in which LDS saves operators both operating expense and capital expenditure, the dynamic casing hanger seal assembly does as well. The dynamic casing hanger seal assembly has a higher lockdown capacity than the industry-standard seal assembly, which allows this seal to be run downhole without installation of an LDS. Because of this design, running the casing hanger seal assembly could save between three and five trips into the well, reducing overall risk.

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