16 January 2013 Last updated at 07:31
A pipeline system servicing up to 27 oil fields has been shut down after a leak on the Cormorant Alpha platform, north-east of Shetland.
The fields affected, and another eight associated platforms, produce up to 6% of the UK’s oil and gas output.
Hydrocarbons were detected inside a leg of the Cormorant Alpha platform.
Its operator, Taqa Bratani, has removed non-essential workers as a precaution and said the leak had been contained.
Shutting down the platform, which is about 100 miles from Shetland, affects the whole Brent pipeline system.
The oil leak at Cormorant Alpha was discovered on Monday and non-essential crew were taken off the installation by helicopter.
Taqa, also known as Abu Dhabi National Energy, said nothing had leaked into the sea and a technical team was investigating the source.
The BBC understands the rest of the Brent pipeline system can no longer operate because Cormorant Alpha, which is situated some 94 miles from Lerwick in Shetland, is a crucial pumping station.
Eight other platforms have shut down with up to 27 North Sea fields affected.
Oil and Gas UK – the offshore industry body – said oil transported through the Brent pipeline system represented between five and six percent of the UK’s North Sea oil and gas production.