Oil giant BP and partners are to invest £3bn in redeveloping two oil fields off the Shetland Islands.
The company believes 450 million barrels of oil could be extracted from the Schiehallion and Loyal oil fields which lie to the west of Shetland.
The fields in the north Atlantic Ocean have produced nearly 400 million barrels since 1998.
BP is undertaking the work with other oil companies - production is due to start in 2016.
BP will have a 36.3% stake in the venture, as will Royal Dutch Shell, Hess Ltd will hold 12.9%, and Statoil (UK) and Murphy Petroleum 4.84% each.
Trevor Garlick, the regional president of BP's North Sea business, said: "The Schiehallion and Loyal oil fields are established assets with a strong future, and we and our co-venturers are taking some significant steps to maximise the greater potential we now see in these fields."