Contracts worth more than £1 billion have been awarded to dozens of UK-based companies for a major redevelopment of two oil fields, operator BP has announced.

The firms will provide services and equipment to redevelop the Schiehallion and Loyal fields to the west of Shetland.

The fields have produced nearly 400 million barrels of oil since 1998 and it is thought a further 450 million barrels could still be extracted from the sites on the North Atlantic margin.

In July 2011 the oil firm and its partners announced their intention to invest £3 billion to redevelop both fields in a project known as Quad 204. The money is going into new facilities to extend production over the next two decades and possibly beyond.

Trevor Garlick, BP's regional president for the North Sea, said: "The UK-based subsea engineering industry offers great expertise and capability and is fully engaged in developing highly advanced equipment that will ensure we maximise recovery from this field until 2035 and beyond.

"It is great to see more than 30 companies from all parts of the UK working together to contribute towards this important offshore project."

The revamp of the fields, operated by BP on behalf of its partners, involves two key elements.

One will replace the existing Schiehallion floating, production, storage and offloading vessel with a new one which is scheduled to be installed in 2015. The new vessel will be 270 metres long and able to process and export up to 130,000 barrels of oil a day and store more than a million barrels.

A major upgrade of the subsea infrastructure is also planned.

Production on the new facilities is set to begin in 2016.

BP said OneSubsea was awarded the latest contract, worth £65 million, to manufacture subsea "trees" in Leeds.

It follows awards made since last year to companies based in Aberdeen, Bristol, Fife, Leicester, Newcastle, Shetland, Wirral and other UK locations, taking the total value of the contracts to more than £1 billion.

UK Business Secretary Vince Cable said: "As I saw for myself at the Offshore Europe conference in Aberdeen last week, Britain's oil and gas industry continues to thrive. Its expertise and innovation is impressive.

"Employing over 400,000 people and providing the majority of our energy needs, the Government's industrial strategy will help keep this important sector growing.

"An important part of the strategy is re-energising the British supply chain. I want to create the conditions for the SMEs (small and medium-sized enterprises) across the country to flourish in a highly competitive global market. So it's encouraging that the UK supply chain have played a major role in the development of BP's Quad 204 project and I hope more will follow."