A brand new platform is set to replace three old ones at the Valhall oil field off the coast of Norway. The new platform is being built by BP to replace the old platforms that have come to the end of their 25-year design life.

The new production and hotel platform became operational in 2010 and will extend the life of the field by 40 years.

The problem

BP and cable company Nexans are working together to make offshore drilling history. They plan to make Valhall the world’s first offshore oil field to receive all its electricity from land through submarine cable, with no need for on-platform generation.

The benefits

By supplying the electricity from land via submarine cable, the oil field will benefit from increased cost-efficiency and reduced emissions, compared to fields where diesel or gas generators are located on the platform itself.

Nexans will manufacture, deliver and install 292 km of HVDC (High Voltage Direct Current) maritime cable, as part of a delivery that also includes fiber-optic submarine cable and equipment.

The solution

To get the electricity to the oil rig, Nexans produce a Valhall power submarine cable which is mass impregnated. The insulation consists of paper impregnated with a high-viscous compound.

When the electrical current flows in the conductor, it heats the submarine cable, and the cable compound expands resulting in a pressure rise.

For the Valhall high-voltage submarine cable, Outokumpu was chosen as the stainless supplier.

Stainless steel tapes are applied helically around the submarine cable to provide transversal reinforcement for the insulation system.

An illustration of the type of high-voltage subsea power cable used in the Valhall project. Courtesy  of Nexans

The new Valhall platform of BP. Courtesy of Nexans

The results

Outokumpu Thin Strip Kloster in Sweden has been a steady supplier to Nexans Norway for over 15 years, providing thin strip for cable armoring.

A Nexans representative explains what they look for in a stainless supplier and why Outokumpu fit the bill: “First and foremost, the stainless steel tape must perform in our submarine cable manufacturing process without causing any problems such as breakages or reduced manufacturing speed.”

He continues: “Our stainless steel suppliers must meet our strict technical requirements set forth in our material specification, which addresses the quality of material and how the product should match our manufacturing process.”

Lars Willborg of Kloster adds: “Because we are supplying for a project, perfectly-on-time deliveries are another must, and we are able to meet it well”. The deliveries are made directly from the mill to Nexans Norway. Outokumpu’s sales company in Oslo, Norway serves the crucial task of liaising locally with the customer.