A second oil leak has been discovered from an offshore platform in the North Sea, it was revealed Tuesday.
An estimated 216 tonnes (1,300 barrels) has already spilled into the sea following the initial spill, which began at the Gannet Alpha platform 112 miles east of Aberdeen last Wednesday.
Glen Cayley, technical director of platform operator Shell's exploration and production activities in Europe, said the main leak was "pretty much dead" but a small secondary leak was proving a challenge.
Around two barrels a day (80 gallons) are leaking into the sea, compared to hundreds of barrels a day at the start of the incident, Shell said.
In a statement, Cayley said "the leak that we've stemmed was in the flow line so job number one was to close in the wells and isolate the reservoir, which of course is the large volume from the leak.
"We're confident that it's under control. The residual small leak is in an awkward position to get to.
This is complex sub-sea infrastructure, and really getting into it amongst quite dense marine growth is proving a challenge.
"The primary leak in the flow line is pretty much dead.
"There is a small secondary leak created by that which is the small flow of two barrels a day which is proving a little difficult to get to and isolate." He said it is not known how the leak initially happened, and it was first spotted by a helicopter flying overhead. At its peak the sheen on the surface extended 18 miles but Shell said this has now diminished.
Cayley said there was strong evidence that sea conditions were naturally dispersing the oil. The estimated spill outstrips annual spill totals for the past decade, according to figures from the Department of Energy and Climate Change (DECC).
The total amount of oil discharged into the North Sea in 2009 was 50.93 tonnes.
Cayley said "shell deeply regrets this spill. We work very hard to ensure that we secure the environment and when we fail in a situation like this, we act swiftly as we've done in this case in respect of setting up our emergency team and informing and working closely with Government agencies.
"We have moved, we believe, really quickly in terms of technically stemming the leak." The spill is described as a light crude oil with a low wax content. Hydraulic fluid is also present. Environment groups have raised their concerns for wildlife in the area. Shell has a standby vessel monitoring wildlife in the area. Cayley said they had no direct evidence of any birdlife damage.