THE safe removal of up to 660 tonnes of oil from the damaged pipeline in the Gannet field in the North Sea will take weeks, Shell has revealed.
Divers closed the leaking valve on Friday, more than a week after the spill was detected on August 10.
Yesterday Shell said 72 concrete mattresses had been laid to secure the pipeline to the seabed 113 miles east of Aberdeen, with more put in place in the next few days.
A Shell spokeswoman said: “Work has begun to evaluate the various options for evacuating the remaining mixture of gas, oil and water in the pipe. This process will take a number of weeks. Once it is completed, plans will be put to the secretary of state’s representative for his approval.”
Hugh Shaw, the UK Government’s representative for maritime salvage and intervention, said: “The risk of further oil release has consider-ably reduced following a successful operation to return raised sections of the pipeline to the seabed with concrete mattresses. The latest survey shows a few sections are lying just above the sea floor but operations continue to add additional mats to reduce the risk further.
“A slight sheen was reported in the area yesterday morning and I believe it is inevitable that further sheens will be seen as we move to the dredging and inspection phase of the operation and oil is released from sediment on the sea floor. Dredging and inspection operations to try to ascertain the precise source of the original leak began earlier today. Weather permitting, these may take three to four days to complete.”
Shell said monitoring was being carried out to make sure no more oil is released.
Shell said: “Small sheens have appeared from time to time as dredging work is carried out to establish the source of the original leak. They have quickly dissipated and it is to be anticipated that this will occur occasionally as work disturbs the seabed.”
More than 200 tonnes of oil leaked into the sea in this month’s incident at Gannet.