A Case History: The Installation of a Damaged Control Line Replacement Safety Valve System in a North Sea Well

Abstract

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: A new safety valve landing nipple in the production tubing using a specially modified seal bore production packer. A new wireline safety valve that would be landed in the new landing nipple A new control line and special control line connector installed inside the production tubing. 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.