UPDATED Shell: leak continues from Gannet field

Residual North Sea leak continues from valve next to original source

The Shell/ExxonMobil Gannet Alpha Platform: reservoir isolated, pipe isolated and depressurised, but small leak continues.
The Shell/ExxonMobil Gannet Alpha Platform: reservoir isolated, pipe isolated and depressurised, but small leak continues.

UPDATE 2 17/08/2011: Shell says the flow rate from the leak is down to one barrel of oil per day.  The company has now attributed the leak to a failure in their mainenance programme at Gannet Alpha, and has apologised for the leak and resultant spill, reported to stretch for 18 miles on the surface of the North Sea.

The Press and Journal reports that Shell's technical director Glen Cayley admits several hundred tonnes of oil remain in the ruptured flowline which is yet to be secured, though he says the surface sheen has already been substantially dispersed by rough weather.

Shell says that a major incident room has been set up to deal with the crisis and to develop an engineering solution. 

“It has proved difficult to find the exact source of the leak because we are dealing with a complex subsea infrastructure and the leak seems to be coming from an awkward place surrounded by marine growth,” Cayley says. “It has taken our Remote Operated Vehicle (ROV) inspections some time to establish exactly where the source is.”

Environmental groups, most stridently Greenpeace, are claiming that the North Sea spill shows that Shell cannot be trusted to open the deep, offshore fields of the Arctic to exploration and production.

UPDATE 1 17/08/2011: Shell now reports via Twitter that the leak rate from the Gannet Alpha well has reduced to less than one barrel (42 gallons) per day.

In an update to its initial company statement on Sunday, Shell has today confirmed that the Gannet Alpha oil well - operated by Shell on behalf of itself and Esso, an ExxonMobil subsidiary - continues to leak crude into the North Sea from a depth of 300 feet.

A video of an aerial view of the slick is available at the Guardian.

In a BBC Radio interview this morning, Glen Cayley, technical director of Shell’s European exploration and production activities, confirmed that Shell has closed in the well and isolated the reservoir, but that a second and much smaller leak from a relief valve adjacent to the original flowline leak source continues to emit hydrocarbons.

Shell is treating it as part of the initial leak with a combined flow rate of "less than 5 barrels per day", or 240 gallons. The Associated Press says Shell have revised this down to 2 barrels per day. 

A Shell spokesperson has told the Guardian that the remianing flows are limited to the residual crude in the pipeline and the company is working to end this residual leak.

Sub-sea engineers Rockwater, a wholly-owned subsidiary of Halliburton KBR (since de-merged) since 1992, won the contract to supply flowline to the Gannet Alpha rig in 1996.

The leak was not discovered by Shell on the platform, but was reportedly spotted by a helicopter flying over the Gannet field last week. The exact start time of the leak is unclear as Shell waited until the leak had been quantified before announcing its existence to the media.

By Monday 56,400 gallons of oil had leaked from a fault in a the flow line system servicing the well - located 112 miles east of the Scottish city of Aberdeen - into the North Sea. Shell has not disclosed a leak flow rate, but estimates the leak as of this morning totals 1,300 barrels or 216 tonnes.

Cayley has called the spill “significant,” but said he believed that waves would disperse the oil sheen and that the spill was not expected to reach the shore. The spill is now thought to be the North Sea's worst since 2000, on the basis of UK Department of Energy and Climate Change figures. 

Shell says that a standby vessel, the “Grampian Prince”, remains on station monitoring the area, with oil spill response equipment and dispersant available if required.

After taking media criticism for allegedly stonewalling the UK's Royal Society for the Protection of Birds, Shell has now confirmed they are in touch with the charity about any potenial impact to wildlife. Cayley said they had no direct evidence of any birdlife damage.

The Gannet oil field reportedly produced 13,500 barrels of oil per day on average between January and April of this year.


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