Ocean Kinetics - The Engineering Experts

Massive rig takes half-time break

Heavy lift vessel Thialf inside the southern limits of Lerwick harbour on Monday morning. Photo Charlie Umphray

ONE of the world’s two largest ocean going cranes is resting up in Lerwick harbour for a week before heading back to complete the biggest current offshore development around Shetland.

For the past three weeks the 137,000 tonne semi-submersible heavy lift vessel Thialf has been installing the legs of the first of two platforms on BP’s £4.5 billion Clair Ridge development.

Thialf was one of the only vessels large enough to cope with siting the 22,000 tonne jacket that will support the drilling and production platform at the field 70 miles north west of Shetland.

Having secured the rig in what the company described as the hardest rock they had encountered in the North Sea region, Thialf was brought to Lerwick harbour in the early hours of Monday morning for a crew change and minor repairs to be carried out.

A BP spokesman said one of the vessel’s 24 ballast tanks had suffered minor damage and needed to be brought into shallow waters to carry out the repairs.

The company hopes the vessel will head back out to the Clair Ridge by the end of the week to install the second jacket weighing 9,000 tonnes, which will be the legs for the living quarters and utilities platform.

The spokesman said: “This is a major milestone for Clair Ridge that we hope will be completed by the end of July.”

The two jackets were built in Norway, while the “topsides” are being constructed in South Korea.

They are due to be delivered on site in 2015 when they will be installed, connected up and tested over a 12 month period before Clair Ridge starts to produce oil in late 2016, if everything goes according to plan.

The vessel’s presence in Lerwick harbour is an indication of the scale of work currently going on around the islands.

The harbour is also playing host to the H-405 barge that is transporting steel piles that will be driven 20 metres into the seabed to support the second Clair Ridge jacket.

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