Royal Dutch Shell shut down the main leak at one of its North Sea oil rigs but is struggling to stop a secondary spill in a hard-to-reach part of the ocean floor.
The company has stemmed the main leak in the flow line to the Gannet Alpha platform by closing the well and isolating the reservoir, said Glen Cayley, technical director of Shell’s European exploration and production activities. The second, smaller leak has proved more elusive.
“The residual small leak is in an awkward position to get to,” Cayley said. “This is complex sub-sea infrastructure, and really getting into it amongst quite dense marine growth is proving a challenge.
“It’s taken our diving crews some time to establish exactly and precisely where that leak is coming from.”
The secondary spill is pumping about two barrels, which is 84 gallons, into the cold water each day. The company estimated Monday 54,600 gallons of oil had spilled into the North Sea from the rig off Scotland’s eastern coast.
Cayley said the company “deeply regrets” the spill, Britain’s worst in a decade.
An investigation is under way to determine the cause of the spill, which they first noticed last Wednesday, Cayley said.
Shell said they stopped the first leak Thursday, but said “the oil found a second pathway to the sea.” Cayley said Shell informed U.K. government agencies of the spill immediately, but did not make it public until Friday. On Saturday it declared the leak had been contained.
Shell said it believes the oil is now leaking from a relief valve close to the original leak. It said once it finds out that is where the leak is, they will stop the spill.
At its largest, the oil sheen covered an area 19 miles wide by 2.7 miles long (31 kilometers by 4.3 kilometers), Cayley said. He said strong waves have dispersed most of it and it would not hit shore.
Shell operates the Gannet Alpha oil rig, 112 miles (180 kilometers) east of the Scottish city of Aberdeen. Shell co-owns the well with Esso, a subsidiary of the U.S. oil firm Exxon Mobil.
The British government said the leak was small compared with the BP spill in the Gulf of Mexico last year, which dumped 206 million gallons of oil into the Gulf — but said it was still substantial for the U.K.’s continental shelf. It agreed with Shell’s predictions the oil would disperse naturally.
Britain has already beefed up its inspections of the 24 drilling rigs and 280 oil and gas installations in its part of the North Sea in the wake of the 2010 Gulf spill.