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6 more of the biggest offshore structures in the world

04/12/2018
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Following our recent article listing 6 of the largest offshore structures in the world, we’ve received many questions and comments about other oil platforms and rigs that didn’t make the cut. 

The Troll A oil platform - one of the biggest structures ever moved - and once listed in the Guinness Book of Records as the biggest oil rig in the world
(Troll A - Image via Heidelberg Cement Group)

Of course there are many different criteria when it comes to the “size” of these structures. Are we going by square footage of the platform? Height from the seabed? Height above water level? Or capacity for oil?

However you determine it, each of these incredible offshore structures is an impressive site. And so - in the interest of celebrating a few more massive feats of engineering - we’ve put together this follow-up list, including some fan-favourites that were missed out last time. 

So crane your neck skyward and marvel at the magnitude of six more of the biggest oil rigs and platforms in the world:

Troll A being moved in to position off the coast of Norway - the four legs are built from steel reinforced concrete formed in one continuous pour to withstand the pressure of the ocean
(Image via Reddit)

Troll A

Once officially named as the biggest oil rig in the world by the Guinness Book of Records 1996, the Troll A oil platform has since been stripped of its title by the likes of Petronius and Berkot.

Nevertheless, it remains an impressive piece of structural engineering, standing at a height of 472 metres (1549ft) above the seabed, with over 300 metres below the waterline.

The platform sits on four legs, each made from mathematically joined, slip-formed conical cylinders that flare out smoothly to have a greater diameter at the top and bottom. The legs are built from steel reinforced concrete, formed in one continuous pouring to allow them to withstand intense pressure from the ocean, and the structure’s 683,600 tonne weight (1.2 million tonnes with ballast). An elevator in the legs travels from the platform to the sea floor in nine minutes.

When construction was completed in 1996, the platform had to be towed over 200km from the Norwegian village of Vats to the Troll field, 80km north-west of Bergen. This was the biggest structure to ever be moved, in a process that took seven days and was televised as a major event throughout Norway.

The Ichthys Explorer is the world's biggest semi-submersible platform, operating in 250m waters off the coast of Australia
(Image via INPEX)

INPEX Ichthys Explorer

In the Browse Basin, 220km off the coast of Western Australia, is the Ichthys Explorer - a huge floating central processing facility (CPF), named the world’s largest semi-submersible platform.

The immense platform has a total weight of 120,000 tonnes and a topside measuring 130m by 120m. It operates in 250m deep waters in the Icthys field, where it’s permanently moored with 28 connecting chains, weighing more than 25,000 tonnes.

The platform will remain at the field for the entire 40 year lifespan of the project, processing natural gas through a 130km network of subsea well infrastructure, before sending it through an 890km subsea pipeline to the onshore Bladin Point LNG facility.

At peak it produces up to 8.9 million tonnes of LNG and 1.6 million tonnes of LPG annually, with up to 100,000 barrels of condensate per day.

The column-stabilised platform includes hydrocarbon processing systems and utilities plus living quarters for 200 workers.

The Prelude FPSO is the world's largest floating facility and produces 1.2 million tonnes of LNG per year
(Image via Shell)

Prelude FPSO

Also in the Browse basin, you’ll find Shell’s Prelude floating liquefied natural gas (FLNG) project. This is the world’s largest floating facility, with a length of 488 metres (1601ft) and width of 74m (243ft). The deck area is longer than four football fields.

The 600,000 ton facility was moved into position over the Prelude gas field in December 2017, at a water depth of 250m, where it will be moored for 25 years using four groups of mooring chains.

The huge FPSO features gas receiving and processing facilities, control rooms accommodations and storage facilities. It has a capacity of 1.2 million tonnes of LNG per year, with a storage equivalent of 175 olympic swimming pools. Natural gas will be treated and liquefied to -162°C, before being offloaded to LNG carriers for distribution. This hugely benefits production costs, eliminating the need to transport the gas first to an on-shore LNG facility for liquefaction.

The Tombua-Landana platform is one of the tallest oil platforms in the world, and is supported by four CPT legs fixed to the seafloor by 12 foundation piles
(Image via David Burn)

Tombua Landana

At a water depth of 1,200ft, 80km off the shore of Angola is the Tombua-Landana project, a joint development of the Tombua and Landana fields operated by Chevron.

The Tombua-Landana platform sits at a height of 1,544ft - just shorter than the Petronius, Baldplate or Bullwinkle platforms - on a 56,400 ton four-legged CPT that’s fixed to the seafloor by 12 foundation piles. In total, the platform has a mass of 81,500 short tons.

The project was the first to use a tender-assisted drilling rig for a fixed structure in deepwater and includes sulfate removal membranes for seawater treatment. 38 well slots work to a capacity of 130,000bpd of oil and 210MMcf per day of gas. It includes two export pipelines to remove the gas and oil from the fields.

The $3.8bn project came onstream in September 2009, supported by 120 offshore jobs with accommodation provided on the platform. It’s expected to recover 350 million barrels of oil equivalent over the project lifespan.

The Blue Whale II is yet to begin operations but is one of the biggest rigs ever built and will drill to a depth of 50,000 feet
(Image via CTGN)

Blue Whale II

The Blue Whale II is a Chinese self-propelled drilling rig that can operate in 3,658m (12,000 ft) of water and reach a depth of 15,240m (50,000 ft) - around double the height of Mount Everest.

The purpose of drilling so deep is to mine “flammable ice” - a methane hydrate which has been found under the South China Sea. This gas is formed by sub-zero temperatures and intense pressure more than 30 times greater than the atmosphere. It’s thought that one cubic metre of can produce the energy equivalent of 164 cubic metres of ordinary natural gas. 

Blue Whale I was the first project to mine this gas, with Chinese media reporting the successful first production in May 2017. Blue Whale II is a much larger platform, at 123m x 93m, with a height of 118m and weight of nearly 43,725 tonnes. Construction was completed in November 2017, but operations are yet to begin.

Being self-propelled it can travel at up to 10 knots to the optimal position in the field, and can withstand high speed winds up to 125 miles per hour. 

The Magnolia Extended Tension Leg Platform is listed in the Guinness Book of Records as the tallest structure in the world
(Image via ConocoPhillips)

Magnolia

The Magnolia Extended Tension Leg Platform is considered by the Guinness Book of Records to be the world’s tallest structure. 

At a height of 1,432 metres (4,698 ft) it dwarfs the likes of the Burj Khalifa, the Petronius platform and the Troll A platform. However, some dispute the classification due to much of the “height” being made up of the length of tendons that attach the floating platform to the sea floor. 

The Magnolia field is located in the Gulf of Mexico, around 180 miles south of Cameron, Louisiana. Production began in 2004 and by 2007 was reporting a cumulative production of 29 million barrels of oil equivalent. The platform is designed to handle a capacity of 50,000 barrels of oil per day and 150 million standard cubic feet of gas per day.

The tension leg platform (TLP) consists of four cylindrical columns connected below the waterline by a rectangular pontoon frame. At the base of each column, two steel tethers descend to a pile foundation on the seafloor, to hold the platform in place. Each pile is 8 feet in diameter and 339 feet long. They’re driven about 319 feet in to the seafloor. 



(Image via Shell)

Honourable mention - Bullwinkle

 The Bullwinkle fixed steel oil platform was installed in the Gulf of Mexico in 1988 and was, at the time, the tallest structure ever built, at a height of 529m (1,736ft).

The 50,000 tonne project used 10 times the amount of steel as the Eiffel Tower and took five years to construct - with 2.5 years spent just building the jacket.

Though it has now been surpassed in size by the likes of the Petronius, it’s still considered an extraordinary engineering feat. For many it’s worthy of inclusion in any list of massive structures, if only as an excuse to see the above picture featuring the jacket being towed 332 nautical miles on an 853 ft barge (another “world’s largest” at the time) from Texas to the offshore field.

 

Each of these structures can be considered, in one way or another, one of the biggest in the world. But there are always a few more worthy of recognition. What did we miss? Which gigantic structures, old or new, deserve to make the cut? Let us know and maybe we’ll follow up again with “Even More Of The Biggest Offshore Structures In The World”.

Looking for an offshore job on one of the world’s biggest structures?

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Recent Comments
What about the BP Magnus jacket built by Highlands Fabricators at their Nigg Yard. I have an old photo of it being built if needed.
Charlie Rhoden, 06 December 2018
Please confirm/revise the production numbers for Magnolia. The natural gas number seems reasonable for a daily rate however the crude oil and NGL numbers would seem to be more properly annual rates. The Magnolia field is located in the Gulf of Mexico, around 180 miles south of Cameron, Louisiana. Production began in 2004 and by 2008 was was producing an average of five million barrels per day of crude oil, ten million cubic feet per day of natural gas and one million barrels per day of natural gas liquids.
Tom Maunder, PE, 06 December 2018
@Tom Maunder - Thanks for your comment. Having revised our data we believe you're right, those numbers were incorrect. We've updated the listing with information from a more accurate source. @Charlie Rhoden - Absolutely, send them to feedback@fircroft.com and we'll see if we can include it next time.
Fircroft, 06 December 2018
What about the Hebron GBS and topsides platform offshore Newfoundland?
Manuel Bandeira, 06 December 2018
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6 more of the biggest offshore structures in the world - Time to read 8 min
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