Greenpeace activists have launched a protest near Shell's Brent Charlie platform north-east of the Shetland Islands, criticizing the oil giant's decommissioning plan for the Brent oil and gas field, the field that gave name to the crude oil benchmark that is used to price the biggest part of the world’s internationally traded crude oil.
Shell's plan for the field that started production in 1976 is to remove the topsides of the four Brent platforms to shore for recycling, leaving the legs and the lower part of a steel jacket in the sea.
The company has so far removed topsides of three platforms from the field - the Brent Delta, Brent Bravo, and last month the Brent Alpha, and carried them to Hartlepool for Recycling.
The three platforms' topsides were all removed by Allseas' giant Pioneering Spirit vessel, in singe lift procedure. The 10100 mT Brent Alpha jacket was removed in July by Heerema's behemoth crane vessel Sleipnir and brought to the AF Miljøbase decommissioning site in Vats, Norway, where it will be recycled.
What is left at the field are the Brent Charlie, and the concrete legs of the Brent Delta and the Brent Bravo. The Charlie topsides are planned for removal, but the concrete legs, which contain oil as well as contaminated water and sediment, are planned to be left in place, in what Greenpeace has labeled a "ticking time bomb," given the chemicals the legs' storage cells contain.
"Shell estimates three of those platforms contain 640,000 cubic meters of oily water and 40,000 cubic meters of oily sediment with a total content of more than 11,000 tonnes of oil," Greenpeace said.
According to Shell's website, removing the legs poses a bigger risk to people and the environment than leaving them in place.
As for the content of the concrete legs' storage cells, Shell has said that the sediment contained in the base of the concrete storage cells on Bravo, Charlie, and Delta "contains no significant non-biodegradable compounds."
"It is a sticky mixture of about 50% water, 25% sand and grit, and 25% oil particles attached to the sand and grit. It does not flow and is difficult to move. Independent laboratories have scrutinized the samples," Shell has said.
Shell has said it has studied two options for removing the sediment; to remove and inject it into subsea wells, and one to pump it into tankers and take it to shore.
"Both would be technically difficult and present significant safety risks to people working on them, on balance with only a minor benefit in terms of reducing the legacy environmental impact," Shell has said.
In October last year, the member states of the OSPAR Commission (Convention for the Protection of the Marine Environment of the North-East Atlantic) met in London and discussed Shell’s plans, with the UK government indicating its approval.
"The German government lodged an official objection. The EU Commission, Sweden, Belgium, Denmark, and the Netherlands also spoke out against leaving 11,000 tonnes of oil in the concrete tanks on the seafloor. But the final decision has been postponed and is pending.
"An approval from the member states would set a dangerous precedent for other oil companies and further the destruction of the North Sea," Greenpeace said.