The addition of a new well slot to a major operator’s gas platform in the UK Irish Sea will significantly extend the production life of the facility. As is often the case offshore, the project was not without its challenges and called for flexibility on the part of all concerned, not least Acteon company Claxton.
Claxton was initially sub-contracted to design, fabricate and install a new conductor guide and centraliser in the platform’s splash zone. Fitting the new guide, a great team effort with main contractor PSN’s construction team, was a complete success; the guide was lifted over the side of the platform, slung into place within the jacket structure and firmly secured within a few hours by a crew of four abseilers. The picture <opposite> shows perfectly what was involved.
Thereafter, there were some changes to the original plan. With the field operator’s drilling crew on site and preparing to drill the conductor socket, concerns emerged that whipping of the drillstring at the congested cellar deck level might lead to clashes with surrounding steelwork or piping. “The general feeling was that the provision of a drill bush in the guide at the splash-zone level would not be adequate to contain the problem and that a temporary guide was required at the cellar deck,” explains Bob Leggett, Claxton’s project manager for the work. “As we were already involved in the project and have a lot of previous experience with this type of work, we were asked to come up with a solution to the problem.”
Claxton’s answer was to install a temporary guide in the opening through the cellar deck and to provide a bush that could be run on the drillstring to sit in the guide. Once landed in the guide, the bush, which had a polymer lining and formed a clearance fit around the drillstring, was locked in place to provide the necessary restraint at the critical point. With the initial drilling complete, the temporary guide was removed and the conductor was run into the hole.
In another departure from the plan, the drilling crew decided not to install the conductor centraliser within the splash-zone guide. This was because they were concerned about problems engaging the centraliser in the guide and the effect this would have on the drilling schedule. A different type of centraliser was therefore called for, one that could be handled and installed by abseilers, like the guide itself. With the agreement of PSN and the operator, it was decided to construct the centraliser in three segments. This allowed the centraliser to be retrofitted in the guide on completion of the drilling activities. Again, the installation of the guide was a joint effort with the PSN construction team and turned out to be a complete success.
David Pugh, PSN’s project engineer says, “Projects involving a number of responsibility interfaces are prone to unforeseen change. The project team has to be flexible and able to respond quickly when deviations to plan occur. Claxton has a lot of experience of drilling-associated work and was able to provide that quick response with an efficient design, build and install service. The Claxton staff were valuable members of the project team and brought with them a positive attitude to problem-solving.”
Bob Leggett takes satisfaction from having been part of an imaginative project to prolong the life of an installation that was past its production peak. He says, “Claxton has previously undertaken projects to regain entry to reservoirs via existing well slots, so-called slot recoveries. By adding an entirely new slot you minimise the effect on production from the existing wells; though, as here, you have more structural issues to deal with. Each approach has its advantages. What is important is that the range of options available to operators seeking to extend the life of existing structures has been extended.”
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