One hundred and eighty-six kilometres off Scotland's Shetland Islands
stands Shell's Brent Alpha platform.
After almost half a century, this giant structure is being dismantled.
It's an epic engineering challenge,
ten years in the planning,
safely lifting almost 30,000 tonnes from the North Sea -
one of the most hostile environments on Earth.
Oh, man, that's...
That's something.
Brent Alpha,
it's the third of four Brent field oil and gas platforms
being removed by Shell.
Built during the 1970s energy crisis,
Alpha's structure is unique among the Brent platforms.
Its sister platforms, Bravo, Charlie, and Delta,
each sit on concrete legs buried deep in the seabed.
But Alpha sits on a giant steel frame...
presenting its decommissioning team with both a challenge and an opportunity.
For Brent Bravo and Brent Delta, we lifted the topsides.
There we go!
We brought them to shore and we recycled the topsides.
The construct of Alpha is slightly different.
It sits on a steel structure called a jacket.
That allowed us not only to lift the topsides,
and bring to the shore for recycling, but also that steel structure.
The team plan to cut Alpha's legs in two places.
First, just above sea level, allowing its topside to be lifted.
Then, 85 metres below the waves
to allow the removal of the upper section of its jacket.
Bravo and Delta sit on three very large legs.
We had the opportunity of going inside the legs
and cutting from the inside.
With Alpha, it's a smaller platform which sits on six narrower legs.
We're not able to cut it from the inside,
so we had to figure out a way of how we were going to cut the legs.
To get to the legs of the Brent Alpha jacket and cut them,
we use rope access techniques.
Jon and the team will gear up and abseil down over the North Sea.
This is the boring bit, and then, coming back up is the worst part.
Even on a flat day, there's a swell of 1.5 metres.
It's never flat calm out there.
So, you need real nerve to abseil on top of sea which is moving.
Rope access is a very technically challenging,
specialised skill set,
which allows us safe access to some very hard-to-reach places.
We're down at the bottom of the leg, about nine, ten metres down.
Warren is watching Jon's back whilst he's doing the hot work.
I personally wouldn't want to be hanging five metres from the North Sea.
It's very cold. You're looking at about five degrees.
So, if someone does fall into the sea,
we need to get to them within a matter of minutes
and get them out safely.
We have an Emergency Response and Rescue Vessel on standby at all times.
If someone falls in the water,
they're able to pull them out in under four minutes.
It's not just the chill of the North Sea posing a risk to the decommissioning team.
When a big storm comes through, there are very large waves, up to 50 feet.
So, if we cut the legs straight,
then if a wave hits the platform, we could have some catastrophic outcomes.
Simple horizontal cuts don't provide enough resistance
against the force of storm waves.
We have to develop another way of cutting the legs
so that it can be lifted without it moving in the horizontal direction.
We've made what's called a castellated cut.
These castellations ensure that the topsides cannot slip off the legs.
Cutting interlocking notches and slots increases resistance,
preventing the topsides from sliding while allowing it to be lifted vertically.
For two weeks, the team work around the weather...
Got a storm coming in and it's snowing again.
...until each leg is cut below the platform.
We finished cutting all six legs.
It's been a really tough campaign, very changeable conditions.
It's an historic moment in the life of Alpha.
With cutting complete, the final personnel leave the platform.
-That's the last man off right now. -Yeah.
The challenge now is to lift the platform
using the largest construction vessel on the planet.
At almost 400 metres long, Pioneering Spirit is a giant.
Designed to retrieve decommissioned platforms,
she's capable of lifting 48,000 tonnes.
But Brent Alpha presents a unique engineering problem.
With Bravo and Delta,
we lifted the topsides
by lifting underneath the deck.
Alpha is different
because we are cutting the legs much nearer to the sea level,
and we're using the legs to lift the whole topsides.
To lift the 17,000-tonne platform,
Pioneering Spirit is equipped with these...
a giant set of clamps
designed to clasp Alpha's legs at newly-installed lifting points.
So, I'm standing between the bows of the Pioneering Spirit.
Behind me, you can see the topside's lift system
with the grey horseshoes inside the red lifting levers,
which will extend, grip onto the legs of the Brent Alpha platform and lift.
The most challenging part of the lift will be connecting
all the horseshoes with the platform.
That's an operation which has not been done before.
And then, obviously, the lift itself will be the moment of truth.
As the Pioneering Spirit comes in around Brent Alpha,
if you can imagine, with the swell going on in the North Sea,
it's just a small margin of error, a couple of centimetres,
to make sure that we're coming in and slotting into the lifting points.
With the clamps in place, the team are ready to lift.
The technology on display from Allseas was just incredible.
It was awesome to see such a heavy lift executed with such control.
A real career highlight for me.
Successfully aboard Pioneering Spirit,
Alpha's topside is transported back to the UK...
placed on a giant barge...
and towed into dock to be recycled.
Now, attention turns to the team's final challenge...
cutting and lifting the upper section of its giant steel jacket.
Attempting it requires another record-breaking ship.
The Sleipnir is the largest crane vessel in the world.
Her 114-metre-long cranes
hold the record for the heaviest single jacket removal -
a staggering 8,100 metric tonnes.
Pretty amazing.
Behind me, you see two 10,000-tonne cranes,
which we'll use to lift the jacket.
Alpha's jacket weighs in at around 10,000 tonnes.
Meaning, with a successful lift, Sleipnir will beat her own record.
But before the team can lift, they need to cut.
It's not just the six legs that we have to cut.
There are a large number of supporting bracings,
which keep the structure strong,
and there are conductors and there are risers as well.
So, there are, in total, 43 subsea cuts to be done.
It's a really exciting part of the project
because we're going to use the world's largest diamond wire-cutter.
Basically, we will position it around the legs
and the diamond wire will slice through the leg.
In place, 85 metres underwater,
the cutter loops a thin steel wire, over seven metres long,
around each segment.
Encrusted with industrial diamonds,
one of the toughest synthetic substances known,
the cutter sets to work slicing.
Moving down. Block 75 metres.
The team monitor the delicate procedure
with underwater, remotely-operated vehicles.
Francesco, you can open the clamps.
Opening clamps.
But with four cuts remaining, they must call a halt.
We have a hold point because it is a point of no return.
A little more.
We have what's called a green cut and a red cut.
So, the green cuts mean that if you cut through,
then the jacket still has structural integrity.
It will still sit there by itself.
The red cuts are, essentially, the point of no return.
So, once you've undertaken the red cuts,
you must lift.
We need to make sure that all the equipment,
the people, everyone is absolutely in the right place
and ready to press the button.
This morning, we had the no-go meeting
and the decision was all systems are go and we're ready to lift.
Done? Yeah?
-Yeah. -Alright.
The final four red cuts have now been completed.
The jacket is now completely severed.
We're in a position that the two cranes will now line up.
They will get ready to lift the jacket clear of the water.
As Sleipnir begins the historic lift,
all eyes are on its 550-tonne hooks.
Great. We can speed up those cranes to two metres a minute.
Submerged for 44 years,
Alpha's rusted jacket inches into the sunlight.
Eighty metres is a staggeringly high structure.
So, to watch that come out of the sea,
and it only took about two hours to do it,
was incredible.
I'm used to scale,
but even then, it is like, "Wow! This is really, really big."
It's very exciting to see just over 10,000 tonnes
lifted cleanly out of the water.
If I could sum up in three words how I feel -
happy, excited and proud.
Pride...
satisfaction...
but also relief.
Safely held aloft by Sleipnir's cranes,
Alpha's upper jacket makes its final journey...
sailing from the Brent field to Norway to be recycled.
Sailing up the fjord was amazing as the sun came up.
There's a huge sense of satisfaction for everyone involved
when we see something successfully completed like this.
Over the coming year,
more than 97% of this vast edifice will be dismantled and recycled -
a fitting end to an engineering legacy.
So, that's it.
Three down, one to go.
Bring on Brent Charlie.