Brent Field oil rig decommissioning

Year:2017

Duration:5 days

Cost:Unknown

Country: The North Sea

What did this project achieve?

Remove and recycle a major oil rig platform stuck out in the North Sea

The Brent oil and gas field – 186km north-east of the Shetland Islands – produced its first oil in 1976. It has been one of the most productive North Sea oil fields for over 40 years.

Brent has become less economic recently and owners Shell are currently decommissioning its oil rigs in the area. The Brent Delta was the first of 4 platforms in the field to go.

An oil platform – also known as a topside - can be decommissioned by dismantling it onsite or by cutting it into pieces and floating it away on barges. Supporting legs are sometimes left in the sea where they stand.

Shell decided to remove the Brent Delta topside in one piece. This method had been used before, though not with a platform this big.

The Brent Delta was the height of the London Eye and had a platform deck space about the same size as a football pitch. Weighing 24,000 tonnes, it had been home to 160 people and stood in 140m of water.

After 5 years planning in April 2017 the 382m long lifting vessel Pioneering Spirit slid under the Brent Delta topside and lifted it off its 3 concrete legs in only 10 seconds.

The ship then took 5 days to carry the platform 700km south to Hartlepool where it was dismantled.

Difference the decommissioning made

With around 100 oil platforms set to be decommissioned in the next 10 years the Brent Delta removal has shown the work can be done smoothly and with limited environmental damage.

Brent Delta will be 97% recycled. This should demonstrate that oil rig decommissioning work need not have a major impact on the environment.

How the work was done

The Brent Delta platform removal took 5 years of study, preparation and engineering work.

Preparation saw engineers strengthen the platform underdeck, install lift points on the rig and cut through the 3 massive concrete legs that the platform stood on. Unlike most other rigs - which have steel legs - Brent Delta sat on reinforced concrete columns.

Offshore engineers Allseas built the 382m long lifting vessel Pioneering Spirit specially for the Brent Delta job.

The twin-hulled colossus was built in South Korea and designed to straddle an oil platform and remove an entire topside in a single lift.

Pioneering Spirit is the same length as 6 jumbo jets sitting nose to tail. The vessel looks a bit like 2 ships welded together side to side but with a gap the width of an oil rig in between. It's equipped with 16 hydraulic lifting arms.

The Brent Delta removal was the heaviest ever marine lift and a world record.

"​‌

Fantastic. Probably the best thing I've ever seen in my career.

Robert Cullen

Former Brent Delta worker, watching the lift on 28 April 2017.

Fascinating facts

The Brent Delta platform weighs the same as 2,000 London buses.

The oil rig is the first major piece of infrastructure to be decommissioned in the North Sea.

More than 100 platforms are set to be completely or partially removed over the next decade in UK and Norway waters.

People who made it happen

  • Client: Shell International plc
  • Main contractors: Offshore engineers Allseas Group S.A.

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