The multi-national oil and gas company also said that the remaining platform, Brent Charlie, would follow suit “in the next few years.” In late 2011 another platform, Brent Delta, was the first to be decommissioned and this marked the beginning of the retirement of the giant oilfield. Shell said in a statement that “from a technically innovative installation phase through to a long period of operation and production, these platforms have helped to sustain vital North Sea oil and gas supplies. We will now focus on safely decommissioning these assets.”

It’s an enormous project, as Alex Kemp, professor of petroleum economics at the University of Aberdeen, explains: “The Brent field decommissioning will be the biggest of all the fields in the UK sector in terms of scale and the amount of money to be spend… The total decommissioning costs will be £4 billion in today’s prices… The sizes of the platforms mean that you can’t be quite sure just how things will work out, even though they’ve been planning it for at least two years.”

The Brent field is situated in the East Shetland Basin – just over a hundred miles north-east of the Shetland Islands. It was discovered in 1971 and production started-up in Brent in November 1976, where oil and gas was exploited on the four platforms in the following four decades. The platforms were among the first in the North Sea to produce oil.

The field was only expected to last for about 25 years, but the discovery of significant amounts of natural gas in mid-1990s helped prolong its output until now. Shell said both Brent Alpha and Brent Bravo had “significantly exceeded” their original expected lifespans.

Peak oil production from Brent was in 1984 – when over half a million barrels were produced each day.

Professor Alex Kemp says that “it was one of the early giants… Of the early generation of fields Brent is the biggest in terms of combined reserves of oil and gas… It was certainly a pioneer.” But he says that “oil and gas will continue beyond 2050 [and] we think it will continue at low levels beyond 2060… But the old giant fields are on their way down, a few will last quite a long time.”

Oil and gas reserves in the North Sea appear to be running out – and since 2007 the UK has explored the possibility of exploiting onshore shale gas through fracking. In the United States, the output from hydraulic fracking now makes up 43 percent of oil production and 67 percent of natural gas production.

John Scrimgeour spent 35 years in the energy industry before becoming director of the Institute of Energy at the University of Aberdeen. He insists that indigenous production needs to be maintained to drive British economic growth:

“We don’t have to produce [oil and gas] indigenously, but, of course it’s not good for your balance of payments if you don’t. If you think historically, large supplies of cheap energy drive economic growth and if you can supply that yourself you’re so much the better.”

The decommissioning of these Brent field platforms will take years to complete. It may well mark the beginning of the end for North Sea oil and gas exploitation. Over the coming decades it will become clear whether the UK finds an alternative to replace this once bountiful source of energy.

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