20 August 2011 Last updated at 09:46 ET

Shell North Sea oil leak operation 'successful'

A diver in murky conditions closes off the leaking valve

An operation to turn off a North Sea platform valve which was leaking oil into the sea has so far been successful, Shell has said.

The company has been dealing with the release of what is estimated to be 218 tonnes of oil from a leak near the Gannet Alpha platform.

Shell said no more oil had leaked from a relief valve which was closed by divers on Friday.

The situation will continue to be monitored, the company added.

Shell said oil had been seeping from the valve at a rate of less than one barrel a day before it was closed.

An operation to place concrete blocks over the pipeline, where the leak was discovered last week, is also continuing over the weekend.

Below surface

In a statement, Shell said: "Shell has set up an investigation team to establish the cause of the leak.

"We will also co-operate with government authorities and regulators as they conduct their own investigations, including supplying them with pipeline integrity reports and other information."

The spokesman added: "We are continuing to monitor the conditions of the sea which affect the dispersal of the oil, in conjunction with Marine Scotland, and to undertake surveys of bird and marine life by air surveillance and vessels in the area.

"These surveys, which include independent bird monitoring, have indicated no significant impact on the environment."

The pipeline - about 300ft (91m) below the surface - contains up to 660 tonnes of oil.

The Gannet Alpha oil platform is 113 miles (180km) off Aberdeen.