Title: How to Decommission CUT DOWN 3 Cell Contents FINAL MASTER 211216
Duration: 5:48 minutes
Description:
The challenges and solutions for decommissioning of the storage cells of Brent’s three gravity base structures.
How to Decommission CUT DOWN 3 Cell Contents FINAL MASTER 211216 Transcript
[Background music plays]
Instrumental music with synthesised effects, at times with softer tones and at other times building to a stronger rhythm.
[Graphic]
Computer generated imagery of the outline of a gravity base structure at frame-left with a pipeline extending towards frame-right, 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]
Cell Contents
[Narrator]
When Brent’s 3 gravity base structures were built in the 1970s, there was no pipeline in the North Sea that could export oil or gas to shore. So the GBS were constructed with cells at their bases to temporarily store oil, before it was offloaded into tankers.
[Video footage]
Low angle panning footage of the legs of the gravity base structure of one of the Brent platforms under construction, seen against the background of a pale blue sky. Bird’s eye view of a vessel in the North Sea against a background of grey waters and skies. Another low angle view of the concrete legs of the gravity base structure under construction. High angle view of wet cement pouring into a mould.
Panning aerial view of the cluster of storage cells, still under construction. Low angle view of the storage cells under construction. High angle view of the ocean and towing vessels below, as from the point of view of the tops of the legs, the storage cells of the base structure visible below.
Interview with John Gillies
[Title]
Brent Decommissioning Execution Manager
[John Gillies]
So this is a model of Brent Delta gravity base structure. You can see at the bottom there are 16 storage cells.
[Video footage]
Mid-view of John Gillies, as he speaks and points to a model of the base structure to his right, visible at frame-left. Low angle close-up of John, panning to a close-up of the storage cells of the model as he points to them.
[Text displays]
John Gillies / Brent Decommissioning Execution Manager
[John Gillies]
And this is a cross section through one of these 16 cells. It’s a reinforced concrete structure. The concrete is around one metre thick.
[Video footage]
Mid-view of John Gillies, as he lifts a cross-section of one of the storage cells. Close-up of the cross section as he points to various parts while explaining the structure.
[Narrator]
There are 64 cells across the whole field, each is 60 metres high and 20 metres in diameter. Before Shell could recommend a method of decommissioning, the team needed to investigate their contents.
[Video footage]
Vertically panning footage of the model of the base structure, cutting to a panning close-up of the tops of the storage cells. Rear view close-up of a man facing a computer screen which displays graphics related to the storage cells. Front view of the man seated at his workstation, cutting back to a close-up of the graphics on his computer screen.
Interview with Alistair Hope
[Title]
Brent Decommissioning Project Director
[Text displays]
Alistair Hope / Brent Decommissioning Project Director
[Alistair Hope]
When we set up this project back in 2006, one of the really big challenges we had, right from the outset, was to be able to get into the cells and sample them. So that's taken us several different attempts and in the summer of 2014, we actually got into the cells on Brent Delta.
[Video footage]
Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment. Aerial footage of equipment being lowered into the water alongside the platform. Underwater footage showing a mass of bubbles as something is lowered into the grey waters.
[John Gillies]
We drilled through the concrete at the top of 3 of the cells and lowered a series of liquid sampling and sediment sampling tools, all the way down so that we could capture physical samples.
[Video footage]
Rear view footage of two workers seated in front of control panels and a bank of screens in a drilling control room, cutting to a close-up of a hand on a joystick, controlling the drilling. Underwater aerial black and white footage of drilling taking place on the top of one of the storage cells. More footage of the screens and an operator in the drilling control room.
Close-up of John Gillies as he speaks, still holding the cross-section of the storage cell at frame-left. More rear view footage of two workers seated in front of the controls and screens of the drilling control room, cutting to a close-up of one of the screens.
[Narrator]
An unlikely partnership also helped the team better understand what it was dealing with.
[Video footage]
Rear view footage of Roddy MacFarlane as he walks between workstations in an open plan office space, cutting to a close-up of a kit bag he is carrying in his right hand, which he is then shown to place on the floor alongside a workstation. Mid-view footage of Roddy MacFarlane lifting the sonar sphere onto the counter of a workstation against the background of a now slightly out-of-focus office environment.
Interview with Roddy MacFarlane
[Title]
Brent Decommissioning Business Improvement Manager
[Roddy MacFarlane]
This is a sonar sphere, which we developed in conjunction with NASA.
[Video footage]
Mid-view footage of Roddy MacFarlane holding the sonar sphere as he speaks, seen against the background of an open plan office environment. Close-ups of the sonar sphere Roddy is holding on the countertop.
[Text displays]
Roddy MacFarlane / Brent Decommissioning Business Improvement Manager
[Roddy MacFarlane]
And what we were able to do with this is to put it down through the cell fill lines and into the storage cells.
[Video footage]
Close-up of Roddy MacFarlane as he speaks, seen against the background of the office environment.
[Roddy MacFarlane]
And on the front we have a small sonar, which is what we used to characterise the volume of sediment that was in the base of one of the cells.
[Video footage]
Footage of the sonar sphere moving through the cell fill lines.
[Narrator]
The sampling and sonar revealed there was about 4 metres of sediment, in 42 of the cells. This material was independently analysed.
[Video footage]
Close-up of particles in motion and of the build-up of sediment. Rear view footage of a man in a white coat and wearing safety googles, standing in front of a computer screen in a laboratory environment, cutting to a close-up of his face as he looks down at the computer screen.
[Alistair Hope]
The samples for the sediment certainly showed that the material was more benign than we thought.
[Video footage]
More close-up footage of particles in motion, cutting back to an extreme wide view of the laboratory environment as previously described. Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment.
[Narrator]
The cells’ contents were revealed to be 25% oil, 25% sand and 50% water.
[Video footage]
Wide-view of the man conducting tests in the laboratory environment, cutting to a close-up of liquid in a beaker and another close-up of particles in motion. Close-up of the man conducting the tests, cutting to an extreme close-up of his face and the syringe and vial he holds in front of it.
Interview with Duncan Manning
[Title]
Brent Decommissioning Asset Manager
[Text displays]
Duncan Manning / Brent Decommissioning Asset Manager
[Duncan Manning]
To all intents and purposes, it's relatively understood, and biodegradable.
[Video footage]
Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment.
[Narrator]
Shell recognised people’s interest in the cell contents, so it set up a task group of interested parties, including academics, scientists and environmental organisations.
[Video footage]
Wide view of a modern office building seen against a pale blue sky. Footage of a model of a Brent platform displayed in a window. A woman walks past the window outside the building as the shot cuts to her shaking hands with Duncan in the reception area before he ushers her through and beyond the reception area. Wide view of a glass fronted building, several flying flags and the landscape beyond reflected in the glass.
[Duncan Manning]
This 16-member body was formed in 2011, to really focus on the options for the cell contents and to ensure that we understood what the thoughts and views of our stakeholders were.
[Video footage]
Wide footage of Duncan and others seated around a large table, cutting to a rear-view close-up of John Gillies and a large screen against the wall beyond him. Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment.
[Narrator]
Shell assessed various options: some for leaving the sediment in place and others for removing it.
[Animated sequence]
Computer generated imagery of the storage cells on the seabed, panning down to show a cross section of one of the storage cells with a yellow pipe reaching down into the cell and demonstrating the proposed actions on the brown layer of sediment in the cell.
[Duncan Manning]
Removing the contents of the cells is a very demanding operation, it would require cutting a hole into the cell itself, so, kind of, penetrating that nearly metre thick reinforced concrete. It would probably need to be quite a large, sizable hole to put dredging equipment into the cells.
[Video footage]
Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment. High angle footage of a man seated at the controls in the drilling control room, cutting to footage of his colleague seated in the chair to his right, his hand on the joystick as he looks at the screens in front of them.
[Narrator]
If this could be achieved, the sediment could either be shipped to shore by a fleet of tankers, or re-injected into the reservoir via a series of new wells…
[Animated sequence]
Computer generated imagery of vessels in the ocean in the area of a base structure which is shown below the surface of the water, resting on the sea bed. A yellow line graphic extends from the vessel above, down into the sediment visible in a cross section of one of the storage cells. A second yellow line graphic then extends downwards from the other vessel at frame right and penetrates the sea bed, continuing belowground.
[Alistair Hope]
It’s an enormous operation it’s a multi season campaign, we think on balance this isn’t the right option.
[Video footage]
Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment.
[Narrator]
The team also considered options for leaving the sediment in place. They worked with specialists at DNV GL to identify and assess any risks, and predict potential environmental impact.
[Video footage]
High angle close up of fingers on a computer keyboard, cutting to a close-up of a computer screen displaying graphics related to the storage cells. 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 attentions on the laptop screens in front of them.
Close-up of a computer screen, a hand pointing a pen at information on the screen. This cuts to a close-up of the female colleague at the furthest end of the table. Close-up of James’ fingers tapping on the keys of his laptop, and panning up to a close-up in profile of his face, his colleagues faces forming part of the out-of-focus background.
Interview with Mark Purcell
[Title]
Principal Consultant, Risk Advisory Services, DNV GL Oil and Gas
[Text displays]
Mark Purcell / Principal Consultant, Risk Advisory Services, DNV GL Oil & Gas
[Mark Purcell]
We’ve had marine toxicologists, marine eco-toxicology, an under-water noise specialist.
[Video footage]
Close-up of Mark Purcell as he speaks, seen against a glass panelled background.
[Narrator]
They considered injecting additives into the cells to attempt to reduce the amount of contaminant.
[Animated sequence]
Computer generated imagery of the storage cells on the seabed, showing the cross section of one of the storage cells with a yellow pipe reaching down into the cell and demonstrating the proposed actions on the brown layer of sediment in the cell.
[Mark Purcell]
While this had benefit, it was limited in its benefit because the cell sediment could be four metres thick but the nutrients will only really affect the top layer of that, maybe 10, 20 centimetres.
[Video footage]
Close-up of particles in motion. Close-up of Mark Purcell as he speaks, seen against a glass panelled background.
[Alistair Hope]
Physics and chemistry aren't really helping us here, because the temperatures are very low, at most eight degrees – sometimes, in the winter, a lot cooler than that. So, rates of reaction are very, very slow.
[Animated sequence]
Computer generated imagery of the storage cells on the seabed, showing the cross section of one of the storage cells with a yellow pipe reaching down into the cell and demonstrating the proposed actions on the brown layer of sediment in the cell.
[Video footage]
Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment. Underwater footage of the seabed.
[Narrator]
They also looked at capping the sediment with a protective layer of aggregates.
[Animated sequence]
Computer generated imagery of the storage cells on the seabed, , showing the cross section of one of the storage cells with a yellow pipe reaching down into the cell and demonstrating the proposed actions on the brown layer of sediment in the cell.
[Duncan Manning]
The additional complexity associated with the capping option was that the sediment itself had a very low bearing capacity, and therefore any capping layer you put on top would likely fall into the sediment.
[Animated sequence]
Continuing computer generated imagery of the storage cells on the seabed, showing the cross section of one of the storage cells with a yellow pipe reaching down into the cell and demonstrating the proposed actions on the brown layer of sediment in the cell.
[Video footage]
Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment.
[Narrator]
To address this, a gravel filler would need to be submerged into the sediment, so the capping layers could then sit on top.
[Animated sequence]
Continuing computer generated imagery of the storage cells on the seabed, showing the cross section of one of the storage cells with a yellow pipe reaching down into the cell and demonstrating the proposed actions on the brown layer of sediment in the cell.
[Alistair Hope]
Cumulatively, we're talking about an enormous volume of material, transferring that all offshore, gravel and then sand and then putting that in each cell. So, all of that requires a large fleet of vessels, multi-year campaign, all the associated hazards of doing that; risks to people, environmental footprint, etc.
[Video footage]
Close-up of Alistair Hope as he speaks, seen against the slightly out of focus background of an office environment.
[Narrator]
Specialists predict that when the cells eventually degrade and sediment is released, any effects will only impact the local environment. So, Shell recommends leaving the cell contents undisturbed.
[Video footage]
Wide footage of James Blackburn, Mark Purcell and a female colleague seated abreast of each other at a table in a conference room, their attentions on Mark’s laptop screen. Close-up of a hand pointing a pen to information on the laptop screen. Extreme wide shot of the three seated at the long conference table. Rear view close-up of Mark Purcell, panning down to the data displaying on his laptop screen. More close-up footage of particles in motion.
[Duncan Manning]
It sounds slightly counter intuitive, but on balance it makes more sense to leave the sediment to degrade naturally as it is, entombed within the cells.
[Video footage]
Close-up of Duncan Manning as he speaks, seen against the slightly out of focus background of an office environment. More close-up footage of particles in motion.
[Text displays]
With thanks to NASA / ROVOP
[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]
© Shell International Limited 2016
