Understanding the project enables Claxton to offer a simplified design for splash-zone centralisers under a North Sea contract.
Claxton’s personal approach to project delivery has seen it provide Total E&P Norge AS with savings of up to 70% for centralisers at the splash-zone level. This contract has also helped to propel the company to the position of de-facto number-one supplier of centralisers in the North Sea: more than 5000 of its units are now installed.
Claxton officially kicked off the first phase of this major contract with Total, which covers the supply of conductor and internal centralisers, deck covers, drill bushings, support frames and associated services for the Martin Linge development on the Norwegian Continental Shelf, in June 2014. However, work to establish the best centraliser option for the project started well before that.
“We met with Total to define best practices for the centralisers,” says Ann Vicens, structures product leader, Claxton. “Often, clients just think about centralisers at the end of the project and do not consider how they interface with other equipment. They are vital for conductor integrity, so it is important to get the design right during the early stages.”
Originally, Total believed it would need a complicated design for the splash-zone centralisers owing to concerns over loads being transferred to the guides after drilling and the expected tight tolerance between the conductor, the centraliser and the guide. To meet these challenges, it originally seemed likely that an adjustable, retractable design would be required. In addition, centralisers at the splash-zone level tend to have the more-demanding specifications, as they are subjected to higher environmental loads and they are more vulnerable to corrosion because of the presence of oxygen and water.
Claxton developed two new concepts to fulfil the initial request, but also carried out some reviews of the available riser analysis reports to ensure that high-specification technology was necessary for the project. “By working together and really understanding what Total needed, we were able to simplify its requirements from a complex, new design to a design that we have used a lot in the North Sea. So, Total got tried-and-tested, more-efficient technology.”
The splash-zone centraliser that Total and Claxton agreed on is, apart from having a simpler, proven design, also 50–70% cheaper than those designed to meet the original, more-complicated brief.
Claxton was also asked to look at the problem of centralisation during spudding and to see if a design for a retrievable drill bushing compatible with the jacket conductor slots was feasible.
Claxton’s previous drill bushing experience was with those that only interface with predrilling templates. The Martin Linge project presented a new challenge in that the drillstring with the drill bushing would need to go through all the upper guides and then centralise on the lower subsea guide, which meant that a retractable design was required.
Claxton worked closely with Total throughout the design of the prototype drill bushing to ensure it would fulfil the offshore requirements. Further work to hone the device will continue during Phase 2 of the Martin Linge project.
“This is another example of how an original idea develops when you work with a client and consider their needs and opinions,” says Vicens.
This project- and client-specific approach has been key to the Martin Linge contract, but it has also helped Claxton reach the milestone of installing more than 5000 centralisers worldwide since 1998.
“During more recent years, we have been quite successful at getting the big jobs. I think this is down to working closely with our clients and getting a better understanding of what they need. We also try to engage with them at the right time. Instead of just waiting for the requirements to come through to us, we try to understand the specific details of each project at an early stage and to ensure that clients understand the importance of getting the centraliser design right at the start.”
The need for unique designs stems from the different requirements around the world. Some existing clients may simply want “more of the same”, whereas others are looking to focus on meeting specific challenges arising from a particular development.
“That is why we create bespoke centralisers for every client. We design each one for a specific platform to maximise the protection it offers to the well conductor,” Vicens concludes.