Royal Dutch Shell has submitted a plan last week to the British government for the decommissioning of parts of its production infrastructure in the Brent Oilfield in the North Sea now that the oil reserves have been depleted in the field.
The Brent oil and gas field is located in the East Shetland Basin of the North Sea, 186 kilometers north-east of Lerwick, Shetland Islands, Scotland, at a water depth of 140 meters.
Discovered in 1971, Shell began production in 1976. The Brent field was considered one of the most productive parts of the UK’s offshore assets, producing almost 3 billion barrels of oil equivalent since 1976, accounting for almost 10 percent of UK production, according to NASDAQ.
The Decommissioning Program
In the decommissioning process, Shell submitted two decommissioning programs (DPs) in a single document to the Department for Business, Energy and Industrial Strategy (BEIS) for review. This will then be followed by a 60-day public consultation period as part of the review process.
One DP covers all the Brent field installations and its 154 wells, while the other DP covers the Brent field’s pipelines. The combined documents also include the company’s recommendations for shutting down and making safe the four platforms, the wells, and the subsea infrastructure.
“After an extensive and in-depth study period, the submission of Shell’s Brent decommissioning program marks another important milestone in the history of the Brent oil and gas field,” Duncan Manning, Brent decommissioning asset manager for Shell, said in a statement, reports United Press International.
If the UK government accepts Shell’s decommissioning recommendations, the company will still need to gain approval from the OSPAR Commission, a body set up in 1992 under the OSPAR Convention to protect the marine environment of the North-East Atlantic.
The four Shell platforms in the Brent field
Perhaps it’s a little-known fact, but Shell has a history of naming its oilfields in alphabetical order after water birds. So they have the Auk, Brent, Cormorant, Dunlin, Eider, Fulmar and others, with Brent referring to the Brent goose. Added to this nomenclature, the geologic fields in the Brent group are all named for Scottish Lochs, such as the Broom, Rannoch, Etive, Ness and Tarbert formations.
Shell’s first platform to be constructed in the oil field was the concrete-legged Brent Bravo in 1975, followed by the concrete-legged Brent Delta and Brent Charlie. The final platform was the steel-jacketed Brent Alpha. The field supplies oil via the Brent System pipeline to a terminal at Sullom Voe, while gas is piped through the FLAGS pipeline ashore at St Fergus on the north-east coast of Scotland.
There is concern regarding the concrete legs of the Bravo, Delta and Charlie platforms. Each of those rigs weighs as much as the Empire State Building and are as tall as the Eiffel Tower. According to the plan, the platforms would be removed but the concrete leg would remain in place.
Concrete legs of three platforms present problem
This presents a problem, say some people because they could become a shipping hazard and after so long a time, when the concrete legs deteriorate, the sludgy oil inside the legs would be spilled into the ocean, creating an environmental problem. But Manning told the Independent that the company’s modeling of the possible problem showed there would be a “very small” impact on the environment.
Manning did admit that what might happen in 250 years’ time was “not an absolute science”, partly because “we haven’t got reinforced concrete of that age.” He also said that the legs had been built to withstand all the North Sea could throw at them. However, and this might be the sticking point, under the OSPAR agreement, the legs must be removed and that is why Shell needs the UK government’s approval to leave them in place.
Lang Banks, the director of WWF Scotland says, “The OSPAR agreement rules are there to make sure the marine environment is protected and those rules should be followed. The main thing preventing this from being done in this particular case is the cost. Shell should do the right thing and remove these potentially polluting materials.”
But even Lang admits that if it is too dangerous to remove the concrete legs, WWF Scotland would not object to them being left in place. A BEIS spokesperson said: “Any decommissioning plan will be carefully considered by the Government, taking into account environmental, safety and cost implications, the impact on other users of the sea and a public consultation.”