Planning on how to safely remove up to 660 tonnes of oil from the damaged pipeline in the Gannet field in the North Sea began yesterday.
It also emerged that the operation by oil giant Shell to use concrete mattresses to secure the pipeline to the seabed could be completed today.
On Friday, Shell divers closed the relief valve from which oil had been seeping at a rate of less than one barrel a day.
Hugh Shaw, UK Government representative for maritime salvage and intervention, said yesterday: “Following the successful closure of the valve, Shell now plan to continue to secure the pipeline to protect it from threats of storm or tidal damage.
“Following discussions over the weekend, last night I advised Shell I am satisfied with its proposals to complete operations to secure with concrete mattresses sections of pipeline that are raised from the seabed. The operation began at first light and, weather permitting, this is expected to be completed over the next 36 hours.
“Planning is now under way for the safe and timely removal of the gas and oil in the damaged pipeline.”
A Shell spokeswoman said no details were available yet on what method may be used, or how long it could take.
Mr Shaw said UK Government aerial surveillance aircraft continued to monitor the Gannet field and surrounding areas.
He said that yesterday morning the aircraft had found a sheen on the water estimated to be up to 0.002 tonnes of oil. It later dispersed naturally.
Mr Shaw said the sheen followed dredging operations near the mattressing operation to identify precisely the source of the original leak.
Shell has now suspended the dredging until all mattresses are laid at the site 113 miles east of Aberdeen.
Environmental charity WWF Scotland called at the weekend for the UK Government to restrict all Shell operations until a full audit of its installations is carried out.
It made the plea after it was revealed that the UK Government’s Health and Safety Executive had censured the oil group 25 times in six years for breaking safety rules. Shell later defended its safety record.
More than 200 tonnes of oil leaked into the sea in this month’s incident at Gannet – the worst UK North Sea oil leak in more than a decade.