Oil Spill in the North Sea

18 Aug 2011

Early last week the Gannet Alpha platform situated approximately 180km east of Aberdeen, Scotland started leaking light crude oil into the North Sea. To date it is believed that some 218 tonnes (1,300 barrels) of oil has leaked from an 8 inch thick pipeline which joins Gannet E and F drilling fields. The leak was only confirmed a couple of days after it started by the operator Shell. The platform continues to operate but the sub-sea line between Gannet E and F has been isolated and the flow line depressurised which should reduce the leak flow.

From 2009 to 2010 there were a total of 10 leak incidents recorded at the Gannet field one of which was considered major. In 2010, at the OSPAR Convention for the protection of the North East Atlantic ministerial meeting, concern was expressed over the ageing of the 50,000 km pipeline network transporting oil and gas and of the 1,300 offshore platforms within OSPAR’s sphere of influence. According to the latest update on Shells’ website on August 15th the current spill rate is less than 5 barrels per day and is coming from a smaller leak which is harder to plug than the major leak due to the dense surrounding marine growth around the pipeline.

The Gannet field was first discovered in 1973, production started in the early 1990’s at a water depth of 95 meters (310 feet) the reservoir depths vary between 2,728m (8,950ft) at Gannet D and 1,737m (5,700ft) at Gannet E. The installation is almost 20 years old and is thus approaching the end of its 20-25 years design life. The field produced about 13,500 barrels of oil from January to April 2011. From the installation the oil is transported through the Fulmar pipeline to Teesside, United Kingdom. Regardless of the design life timeframe the installation will probably continue to operate until the well is dry.

On August 13th a stand by vessel the Grampian Prince was deployed with response equipment and dispersant if required (dispersant Corexit is banned for use in the UK) however the 30 kilometres oil slick has now been broken up by the rough weather and there has been no recorded use of dispersants. The eventual use of dispersants and the oil spill could have long term consequences on fisheries as the waters are known to be the spawning ground of mackerel, lemon sole, norway prout and langoustine.

The oil spill is a threat to marine mammals in the region ranging from minke whales migrating during the summer months, white-beaked dolphins, harbour porpoises and coastal bottlenose dolphins. Harbour porpoises are listed under Annex II of the EU Habitats Directive as well as the OSPAR list of threatened and/or declining species and habitats. The true extent of harm to marine mammals caused by oil slicks is poorly known however it is believed to cause drowning, suffocation and starvation. Grey seals are found close to the shores of Scotland however this does not mean that they will not be impacted by the oil slick as photos released by Scotland’s government marine surveillance agency today show a sheen of leaked oil off the coast.

Scotland is an important breeding ground for a number of bird species all of which could be impacted by the leak. Razorbills breed around the coast of the UK and the largest colonies are found in northern Scotland. Puffin’s breeding grounds are present at only a few sites therefore the species is particularly vulnerable Puffins will migrate through the area following their breeding season. The deep-diving Guillemots seabirds will probably be the species most severely impacted by the oil slick there breeding grounds are found in Scotland including the Orkney and Shetland islands. They are particularly sensitive to oil pollution and will die shortly after diving through an oily patch in the ocean. The OSPAR Convention notes that the number of oily Guillemots washed up in the North East Atlantic has reduced greatly due to a wider awareness of impacts and measures put in place to reduce oil pollution. The Convention uses the species as an indication of oil spills within the North East Atlantic. Current oiling rates of Guillemots is low in the Orkney (4%) and the Shetland (14%) islands compared to more than 50% in the Southern North Sea. Yet following the accident we will undoubtedly see an increase of dead oiled guillemots in the region.



Imprimer cet article Imprimer cet article