Brent Field Alpha Jacket

How to Decommission Brent: Alpha Jacket

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Title: How to Decommission CUT DOWN 4 Alpha Jacket FINAL MASTER 211216

Duration: 4:04 minutes

Description:

The challenges and solutions for decommissioning of Brent Alpha’s steel jacket structure.

How to Decommission CUT DOWN 4 Alpha Jacket FINAL MASTER 211216 Transcript

[Background music plays]

Instrumental music with synthesised effects, at times with softer tones, at other times building to a stronger rhythm.

[Graphic]

Computer generated imagery of the outline of the Alpha jacket footing at frame-left, seen against a dark greenish background with lighter streaks descending from top of frame representing rays of light piercing the dark underwater environment, the shadows and sunlight dappling the seabed.

[Text displays]

Alpha Jacket Footings

[Narrator]

Brent Alpha has a steel jacket support structure which stands in a water depth of 140 metres and weighs 31,000 tonnes.

[Video footage]

Aerial footage of three vessels streaking through the ocean waters at lower frame-left while a large platform vessel follows at upper frame right, carrying a part of the Alpha steel jacket structure. Footage of the steel jacket structure being lowered into the water.

[Narrator]

At the base of its eight legs are “footings”, giant steel piles filled with cement, which pin the structure to the sea floor.

[Animated sequence]

Computer generated imagery of Brent Alpha’s steel jacket support structure, panning down towards the legs where the structure rests on the sea bed. The cement filled footings are highlighted in red.

[Narrator]

Shell is removing the platform or topside, and the steel jacket structure, above the “footings”. Together this will allow for 25,000 tons of steel to be recycled.

[Video footage]

Panning bird’s eye view of the topside against the background of the sea.

[Animated sequence]

Computer generated imagery of the Alpha jacket on the seabed, this time highlighting the steel jacket structure above the footings in red.

[Video footage]

Aerial fast motion footage of the topside being dismantled.

[Narrator]

Shell has considered different options for decommissioning the footings themselves.

[Video footage]

Low angle footage in profile of Duncan and Alistair seated at a workstation, both looking at a document in front of them on the desk. Rear view footage of Alistair holding a pen in his hand and using it to point to a graphic on the screen in front of them.

[Narrator]

It looked at whether it was feasible to cut and completely remove the footings in a single lift, with the steel jacket.

[Animated sequence]

Computer generated imagery of the Alpha jacket on the seabed, yellow rings appearing under the eight footings to denote the cutting of the footings, before the entire structure lifts off the seabed.

Interview with Duncan Manning

[Title]

Brent Decommissioning Asset Manager

[Text displays]

Duncan Manning / Brent Decommissioning Asset Manager

[Duncan Manning]

The positive elements of complete removal is you are leaving the seabed in the same state that you found it in, so you have removed all hazards from the seabed.

[Video footage]

Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment. Underwater footage of the seabed, showing sand particles in motion in the water and fish swimming along the seabed.

Interview with Alistair Hope

[Title]

Brent Decommissioning Project Director

[Text displays]

Alistair Hope / Brent Decommissioning Project Director

[Alistair]

Any option for complete removal requires excavation of the cuttings around the legs of the jacket, so that you can then cut below the mud-line, using some sort of technique like diamond wire-cutting or high-pressure water abrasive cutting.

[Video footage]

Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment.

[Animated sequence]

Computer generated imagery of the footings of the Alpha jacket on the sea bed. Red rings appear around the base of each of the footings to denote cutting of the footings.

[Video footage]

A close-up, cutting to a high angle view, of a jet of water pounding a block of concrete alongside a drill bit cutting into the block of concrete.

[Duncan Manning]

Sounds straightforward but, in reality, that’s a very complex operation, which has a high degree of safety risk of those involved, either through Remotely Operated Vehicles or through divers to actually allow that cut to take place.

[Video footage]

Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment. Panning bird’s eye view of the topside of the Alpha platform seen against the background of the ocean, cutting back to the close-up of Duncan Manning as he speaks. A point of view high angle close-up of a piece of equipment on an arm being guided by a man dressed in hardhat and safety gear on the platform or deck below.

[Narrator]

The team also considered removing the jacket and then removing the footings separately. But both these options are complicated by the existence of piles of drill cuttings around the footings.

[Animated sequence]

Computer generated imagery of the Alpha jacket on the seabed as the jacket structure lifts off the footings, and rises, before the footings also being to rise off the seabed. High angle close-up of drill cuttings around footings which are subsequently highlighted in red shading.

[Narrator]

These shards of rock, discarded during the drilling process contain some contaminants.

[Video footage]

Underwater aerial footage of the drill cuttings on the seabed, small fish also swimming along the seabed.

[Duncan Manning]

So no matter how you go about trying to remove all of the footings, you would have some kind of disturbance effect on the drill cuttings, which is undesirable and does have a negative environmental impact.

[Video footage]

More underwater footage of the seabed, including drill cuttings and small swimming fish. Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment.

[Narrator]

The team also considered a third option: Removing the jacket, but leaving the footings in place. It commissioned independent studies to assess the consequences.

[Animated sequence]

Computer generated imagery of the Alpha jacket on the seabed as the jacket lifts off the footings, leaving the footings in place. The footings are subsequently highlighted in yellow and red.

[Video footage]

Wide footage of James Blackburn, Mark Purcell and a female colleague, seen in profile, seated alongside each other at a long table in a conference room, their attention on Mark’s laptop screen. Close-up of a computer screen, a hand pointing a pen at information on the screen.

Interview with James Blackburn

[Title]

Brent Decommissioning HSE Manager

[Text displays]

James Blackburn / Brent Decommissioning HSE Manager

[James Blackburn]

DNV have had to take into account what is the impact of the jacket degrading over the next, sort of, three to five hundred years, versus the massive amounts of energy and effort and CO2 emissions that would have to take place to actually remove those footings.

[Video footage]

Wide front view of James Blackburn, Mark Purcell and the female colleague seated abreast of each other at the conference room table, their attention still on Mark’s screen. Close-up of James Blackburn, as he speaks, seen against the slightly out of focus background of an office environment.

[Animated sequence]

Computer generated imagery of the footings of the Alpha jacket on the sea bed. Red rings appear around the base of each of the footings to denote cutting of the footings. The footings disappear, leaving eight short bases in the seabed.

[James Blackburn]

The outcome of that for the jacket, from an environmental aspect, is very low impact if we leave those footings in place.

[Video footage]

Rear view footage of Duncan and Alistair seated at a workstation, Duncan holding a pen in his hand and using it to point to a graphic on the computer screen in front of them. High angle view of the two men engaged in discussion at the workstation, looking at the screens in front of them. Close-up of James Blackburn, as he speaks, seen against the slightly out of focus background of an office environment.

[Alistair]

So our recommendation for the Alpha jacket is to take away the top two-thirds of the jacket, to bring that ashore and recycle that and then leave the bottom third of the jacket in place.

[Video footage]

Rear view close-up of a man facing a large chart containing infographics on the Brent decommissioning. Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment. Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment.

[Animated sequence]

Computer generated imagery of the Alpha jacket on the seabed as the jacket lifts off the footings, leaving the footings in place. The footings’ steel structure is subsequently highlighted in yellow.

[Narrator]

The regulations allow for this, if it’s the most appropriate method. Other operators have done the same.

[Video footage]

Aerial footage of the Alpha platform against the background of the ocean. Panning Bird’s eye view of the topside against the background of the ocean.

[Alistair]

In the northern North Sea, where the Brents are, BP's Northwest Hutton platform, for example, left the footings and the cuttings behind; Murchison CNR's platform, also quite close to the Brents, will be leaving their footings and cuttings behind as well.

[Video footage]

Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment.

[Narrator]

Shell recognizes that leaving the footings would create a snagging hazard for fishermen. It would ensure the footings are marked on maritime charts and entered into the FishSafe system.

[Video footage]

Footage of fishing vessels moored in the harbour, cutting to footage of fishermen untangling their nets alongside the harbour, fishing vessels visible in the background. Vertically panning footage aboard a fishing vessel, grey seas and skies forming the background. Close-up of display screens on the bridge of a vessel, cutting to a low angle close-up of a man’s face, panning back towards the screens as he reaches out to press buttons next to one of the screens.

[Duncan Manning]

There's a Fish Safe system which is a computerised system on all fishing vessels in the North Sea, or UK fishing vessels, that have an audible alarm in the cockpit so that fishermen know to avoid the area.

[Video footage]

Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment. Close-up of the display screen, showing fingers operating the buttons alongside the screen; the screen displays maps with symbols and lines that chart the offshore surface and subsea oil and gas structures.

Interview with Bertie Armstrong

[Title]

Chief Executive, Scottish Fishermen’s Federation

[Bertie Armstrong]

We are prepared to live with that…

[Video footage]

Footage of a fishing vessel moving through grey waters, as from the point of view of port side, with land visible in the distance. Footage of a man uncoiling a rope on the deck of the vessel.

[Text displays]

Bertie Armstrong / Chief Executive, Scottish Fishermen’s Federation

[Bertie Armstrong]

…provided all the necessary trials to allow us to fish as close as sensibly possible to anything that’s left, happen. To be absolutely frank, hazard on the seabed is not new. Wrecks and natural features exist already.

[Video footage]

Close-up of Bertie Armstrong as he speaks, seen against an out of focus background of an office environment. Low angle mid view of a man holding up a tablet device. Close-up of the screen as the man navigates it with his fingers, cutting to a side view of the tablet as his thumb flips up the screen.

Close-up of Bertie Armstrong as he speaks, seen against an out of focus background of an office environment, again cutting to the close-up of the FishSafe display screen, showing fingers operating the buttons alongside the screen. Footage of a wave breaking over a rock outcropping.

[Text displays]

With thanks to Able UK / AVC Media Enterprises / CUT UK / ROVOP / Subsea 7

[Text displays]

Shell.co.uk/BrentDecomm

The Brent Field’s equal partners are Shell UK Ltd and Esso Exploration and Production UK Ltd

[Audio]

Shell jingle.

[Graphic]

Shell Pecten centred on a white background with text displaying below.

[Text displays]

Alpha Jacket

Brent Alpha is the only one of the four Brent platforms that has a steel jacket. The jacket stands in water deep enough to completely submerge the London Eye at a depth of 140m below sea level. The structure has eight legs and was built in Scotland before being floated out to position in the 1970s.

OSPAR

For all but the very largest steel structures, current legislation prohibits leaving steel jackets completely in place at sea. However, OSPAR Decision 98/3 recognises that there may be difficulty in removing the “footings” of large steel jackets weighing more than 10,000 tonnes where structures were installed before 9th February 1999. OSPAR Decision 98/3 defines the 'footings' as those parts of a steel installation which are below the highest point of the steel piles (pins) that are used to fix the structure to the sea bed.

Where significant reasons for leaving all or part of the ‘footings’ in place can be demonstrated as preferable compared to returning them to the shore, derogation to leave these parts can be sought.

In terms of what we propose to leave behind, the ‘footings’ of a piled steel jacket are clearly defined in the OSPAR regulations.

Recommendation

After completing a Comparative Assessment, the recommendation will be to leave the steel jacket footings in place due to the engineering challenges and broader concerns associated with their removal. Leaving the footings in place will also allow the drill cuttings pile to be left to degrade naturally.