Full metal jackets

In July, the final two jackets for the Culzean development were successfully installed on location in the North Sea. It is a major milestone for one of Maersk Oil's key projects, which is expected to meet 5% of total UK gas demand. 

Full metal
Photo: Maersk Oil

The Culzean project

  • Maersk Oil operates the Culzean development with a 49.99% interest. Its co-venturers are BP (Britoil) 32% and JX Nippon, 18.01%
  • The field has resources estimated at 250-300 million barrels of oil equivalent
  • Production is expected to start in 2019 and continue for at least 13 years, with plateau production of 60,000-90,000 barrels of oil equivalent per day

The two huge, yellow structures were towed out on barges from the construction yard in the Netherlands. Sitting horizontally on the barges, they were then lifted by the world's largest crane vessel, upended and lowered into the sea.

These two jackets –– the steel structure that supports the deck and topside of a fixed offshore platform, in this case for the central processing facilities and the utilities and living quarters and each weighing more than 7,000 tonnes – have now joined the third, which was installed last year for the early drilling phase. That means all are now in place and awaiting the topsides of the platforms for the Culzean gas development.

"Ever since the design phase we’ve been concerned with future proofing the Culzean installation – these jackets will have a design life of over 40 years, much higher than a typical jacket," says Mike Shirron, Deputy Culzean Facilities Manager.

An advanced GPS system helped steer the jackets into the correct position and once set-down, piling operations began to secure them to the seabed. Piles were placed in each corner, with each of them being driven 50-55m into the seabed using a hydraulic hammer and then secured using grout.

“We installed them using a tried and tested lift method,” says Shirron.

Culzean is a complicated high-pressure, high-temperature (HPHT) field requiring specialised equipment and expertise and its development has now passed the half way mark.

Maersk Oil has reduced the capital costs of Culzean by USD 500 million through improved drilling efficiency and robust upfront design and planning.

“We're in a great place across the board, the project is comfortably on schedule, we’ve developed effective relationships with our suppliers and we’re doing this safely,” says Martin Uruqhart, Culzean Project Director.

Right on schedule

The installation of the jackets is only one part of the busy activity taking place on Culzean . The deck stacking of the topsides was completed in May. Each deck can weigh up to 1,000 tonnes so they were constructed at ground level and then stacked.

“The next big challenge for the topsides’ construction is installing the more intricate equipment – we’re installing 28,000 pipe spools and 900km of cabling,” says Stuart McAuley, Culzean Engineering Manager.

With construction spread across six different shipyards in Singapore and Indonesia, the floating storage and offloading (FSO) vessel Ailsa is taking shape. In the UK North Sea, work has finished to lay the 52km of pipework required to transport gas produced from Culzean to the CATS pipeline that will bring it to a processing terminal in the UK along with the 3.6km pipeline, which will be used to export condensate to Ailsa.

"There is a lot of activity, both onshore and offshore," says Claus Vissing-Jorgensen, Culzean Deputy Project Director and Facilities Manager. “This is a vitally important year in this development, so it’s great that we’re on schedule."