A Case History: The Installation of a Damaged Control-Line Replacement Safety Valve System in a North Sea Well
- Thomas Barratt (Shell UK) | Brian Mark Goldsworthy (Shell) | Stuart Hamilton (Shell UK Ltd.) | Rodger Dale Lacy (Weatherford International Ltd.) | Mike Taylor (Weatherford) | Alistair Ross (Weatherford International) | Shonagh Anne Mackie (Weatherford) | Eric Calzoncinth (Weatherford Wellheads) | Stuart Dennistoun | Jean-Luc Jacob (Weatherford Int.)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 19-22 September, Florence, Italy
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 2 Well Completion, 7.3.3 Project Management, 4.5.7 Controls and Umbilicals, 1.6 Drilling Operations, 7.2.3 Decision-making Processes, 4.1.5 Processing Equipment, 3 Production and Well Operations
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The GA-03 well on the Gannet platform in the UK sector of the North Sea developed a blockage in the safety valve control line that rendered the existing tubing retrievable safety inoperable. In addition, the seal bores inside the valve were scarred and damaged badly enough that a conventional wireline safety valve would not seal. These were the problems confronting the operator as they planned remediation work to return the well to production. Initially a major rig workover had been anticipated to pull the tubing and replace the safety valve and control line. This operation required the use of a Hydraulic Workover Unit (HWU) to perform the work which would carry a multimillion dollar cost.
An alternative method was examined that would allow replacement of the safety valve and control line without pulling the production tubing or making changes to the wellhead configuration. This alternative method was a new concept not previously attempted by any operator in the North Sea. This innovative approach would involve the installation four elements:
1. A new safety valve landing nipple in the production tubing using a specially modified seal bore production packer.
2. A new wireline safety valve that would be landed in the new landing nipple
3. A new control line and special control line connector installed inside the production tubing.
4. A modified lower master valve to allow wellhead penetration for the injection of hydraulic power fluid to the new control line.
This particular combination of tools had never been run together and their installation would have to be accomplished under a severe deadline, as the HWU job had been planned for execution in September 2009. To accomplish this, the entire operation had to be planned, designed, manufactured, tested, qualified and installed in the GA-03 well before the end of the year. It is a great credit to the project team that from initial proposal for use of the new system in July, they were able to achieve the target date of returning the well to production by the end of 2009. This showed the high level of cooperation and collaboration between the operator and the completion tool and wellhead providers.
This paper will describe in detail the system components and the decision processes and evaluations that led to the selection of this alternative repair method. The collaborative efforts between the operator and two major service providers will be examined and discussed and the installation procedure described in detail. The paper will describe why the successful completion of this project marks a significant milestone in the remediation of older producing wells.
The GA-03 well was spudded from the Gannet Platform in 1994 and completed as a horizontal oil producer in 1995 (See Fig. 1). In 1997 the water cut had reached 95% and the well was shut in. In 2003 it was re-opened after a successful coil tubing water shut- off intervention. In 2005 the water cut had again made production uneconomic and a coil tubing drilled sidetrack of 257ft completed with slotted liner into the top of the reservoir was carried out.
In Aug 2007 the tubing retrievable safety valve (TRSSSV) failed and was locked open. Numerous attempts were made to set an insert wireline retrievable safety valve (WRSSSV) but the top seal stacks were always damaged and it was not possible to get them to hold control line pressure.
This inability to get a pressure test made it evident (assumed) that there must be damage to the seal bores and to the tubular areas directly above and below the TRSSSV, although it was not possible to see the damage on CalVid logs.
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