The Statfjord late life project in the North Sea was approved by the UK authorities on 17 June. The Norwegian authorities sanctioned the project earlier this month.
Fifteen per cent of the Statfjord field extends into the UK sector, and a treaty between the Norwegian and British authorities regulates overall management of the field.
Statoil and its partners submitted plans for Statfjord late life to the authorities in both countries in February.
The British Department of Trade and Industry is responsible for sanctioning the changed plan for development and operation of the Statfjord field, which entails the pressure in the reservoir being lowered to recover as much as possible of the field's remaining reserves.
The ambition is to achieve a recovery factor of close to 70 per cent for the oil, and 75 per cent for the gas.