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Prelude FLNG

Lying 475 km (295 miles) north-west of Broome on Australia’s West Coast, the Prelude floating liquefied natural gas (FLNG) platform is a monster of staggering proportions. Just how staggering I hear you ask? Well if we take the largest aircraft carrier in the world, the USS Gerald R Ford, which displaces around 100,000 tons and times that by six, you will arrive at the gigantic displacement of the Prelude FLNG.

It is by far the world’s largest floating liquefied natural gas platform as well as the largest offshore facility ever constructed – however – with countless problems since its arrival in 2017, including a nearly year-long shut down because of electrical problems between February 2020 and January 2021, the Prelude FLNG is in danger of becoming a bloated white elephant the likes of which have never been seen. 

But with operations now underway once again, there may still be hope for this vast steel hulk, which is thought to have cost between $8 billion and $15 billion. In terms of natural gas extraction, the Prelude is very much at the cutting edge but it remains to be seen whether a facility like this in today’s economic climate is even financially viable.      

Supply and Demand

As the issue of climate change becomes more and more acute, resources to supply our ever-expanding energy needs are under the spotlight like never before. Coal and oil have become the two people at the party who nobody really likes, but because it’s their party we kind of have to go along with them for the time being. 

The fear surrounding nuclear energy has grown dramatically, especially after the disaster at the Fukushima nuclear power station in Japan. Renewable energy is now all the rage as nations around the world pour billions into the young industry, but with our energy needs set to increase by 30% between 2015 and 2040, according to the International Energy Agency, the question is can clean energy sources keep up with such spiralling demands. 

Fukushima Daiichi  Nuclear Power Station.
Fukushima Daiichi  Nuclear Power Station.By IAEA Imagebank, is licensed under CC-BY-SA

Then we have liquefied natural gas, which is certainly a fossil fuel but one that is considerably cleaner and more efficient than coal and oil. The use of natural gas stretches back to the late 18th Century in Britain where natural gas produced from coal was used to light houses and streets.

Throughout the 19th Century, it was mainly used for lighting, with the United States becoming the world’s biggest natural gas user and producer, and with pipelines introduced in the 20th Century, it began to be utilized for heating and cooking in the home, as well as in manufacturing and processing plants. 

With natural gas much harder to access than coal and oil, it took a backseat to the terrible twosome during the 20th Century and in 1971, just 1% of global energy came from natural gas. But as we know, the tables have certainly begun to turn. As of 2019, that figure had risen to 24% and my money would be on that figure climbing steadily further in the coming years. 

So just how much natural gas is there? A lot. Estimates are that roughly 196 billion cubic meters(6,923 trillion cubic feet ) of natural gas still lie underground around the world. If our energy needs remained the same and we took the same percentage of natural gas as we today, it would last us around 52 years. 

The Prelude Gas Field

The Prelude gas field was discovered off the coast of Western Australia in 2007 and was the first well dug in an anticipated 12 well program conducted by Shell.

Two years later, the 10th Well, Concerto 1, again struck gold – or gas if we want to be specific – when it found natural gas around 16km (10 miles) away from the first well. The two combined fields are thought to contain in the region of 84 billion cubic meters (three trillion cubic feet) of natural gas. 

These are decent sized gas fields, but far from the largest in the world. Whatsmore, they are quite remote meaning building a traditional platform and then pumping the gas to the shore would not have been practical. Instead, this was deemed the perfect place to try out a new technique and use a floating platform that could be moved to a different location once the gas reserves had been exhausted.  

Building the Platform

A couple of weeks before the discovery at Prelude, Shell had already awarded a front-end engineering and design contract for a floating LNG facility to the Technip Samsung Consortium. As I mentioned earlier, this is a new technology that has never truly been tested on this scale. 

Essentially, Shell was proposing the very first floating (and moveable) facility capable of not only extracting natural gas from the ground but processing it also. Once the gas was extracted it would be cooled until it was liquified then stored in tanks kept at a bone-chilling -161 C (-257 F). Then every now and again a large tanker would moor next to the Prelude FLNG, and the liquefied natural gas would be transferred over, before heading to facilities around the world. Sounds simple enough. 

Production began on this vast juggernaut at the Samsung Heavy Industries Geoje shipyard in South Korea in October 2012 when the metal that would form the substructure was first cut. This is a double-hulled structure, with one hull inside the other to add extra strength, which may well be needed considering the Prelude Gas Field is located within the ominously named ‘Cyclone Alley’. The double hull design has been designed to last 50 years as well as being able to withstand category-five cyclones and even a “one-in-10,000-years’ storm” producing 300km/h (185mph) gusts and 20metres-high (65ft) waves.  

The Turret Mooring System, which will allow the Prelude to weathervane, meaning it can turn slowly in the wind and with the currents, was subcontracted to SBM Offshore and built in the Drydocks World Dubai and is almost 100 metres (328 ft) high with a diameter of 30 metres (98ft). It also weighs 4,300 tons, making it by far the largest mooring system ever built.  

The MEG reclamation unit was built by Fjords Processing in South Korea. MEG stands for Monoethylene Glycol, a substance used in a huge variety of industries but on the Prelude, it would be used to prevent the formation of hydrates and resulting blockages in pipelines and equipment. 

The massive mooring chains that would eventually hold the Prelude in place were smelted in Bilbao in Spain and the numbers here are quite extraordinary. In total, the Prelude’s chains will measure 17 km (10.5 miles) in length and use 24,500 links.

If you combined all of the pipe networks onboard the floating facility it would measure 450 km (279 miles), but that’s nothing compared to the 3,000km (1864 miles) of electrical and instrumentation cables throughout the Prelude. All in all, the floating facility used 260,000 tons of steel – nearly four and half times the amount used to build the Empire State Building. The Prelude FLNG is technically a barge, as it doesn’t have its own power but certainly looks like a massive oil tanker.

The Launch

All of these various pieces gradually made their way to South Korea where they were painstakingly assembled into the titan that we see today. 

In November 2013 the floating facility was first launched but was far from the finished article as its accommodation and processing plants had not yet been installed. Pieces were steadily added to this gigantic floating jigsaw puzzle and by 2015, all 14 gas plant modules had been installed – each weighing in the region of 480 tons. 

In July 2017, the largest towing operation ever seen got underway, with three towboats carefully inching the massive Prelude away from the dockyard in South Korea. Ahead of them was a 5,800-km (3603 miles) journey to the Prelude gas field and considering they would be moving at just 5 knots (9km/h – 5.7 mph) most of the time, it was certainly not a rapid transit.  

On 25th July, Shell announced that the Prelude FLNG had arrived in Australian waters. Soon after, it began its hook-up and commissioning stage with the facility’s 16 mooring turrets, all seabed driven steel piles, 65 meters (213 ft) long and 5.5 meters (18 ft) in diameter, driven down into the ocean floor to secure the vessel.   

The Prelude FLNG 

By the time the vast bulk appeared off the coast of Western Australia another FLNG facility, the Petronas’ PFLNG Satu, had already begun extracting natural gas from the Kanowit gas field off the coast of Malaysia. The Petronas platform had actually been commissioned after Shell’s but had been built much quicker because of its significantly smaller size.  

The Prelude FLNG is 488 metres (1,601 ft) in length, which is around the same height as the Shanghai World Financial Center, currently the 11th tallest structure on Earth. It comes with a beam (width) of 74 metres (243 ft) and has a height of 105 metres (344 ft). As I mentioned earlier, it displaces an unimaginable 600,000 tons and accommodates a crew of between 220 and 240, with around half of these on shift at any one time. The deck of the Prelude is longer than four football fields, although it is almost entirely taken over with storage and processing facilities. 

But some of the most important components are not even onboard the Prelude, but rather directly beneath it. On the ocean floor is the subsea system, which includes wellheads, subsea Christmas trees (stacked vertical and horizontal valves) and production manifolds (structures that direct LNG products from the wells into various flowlines). Essentially, this is the system that draws the gas out of the earth and directs it upwards through four, 30 cm (12-inch) flexible risers and flowlines which connect to the platform above. The subsea system is powered through a steel umbilical wire that runs from the Prelude down to the ocean floor.  

Once the gas comes up it is processed and chilled which reduces its volume by 600 times. The facility has a production capacity of 5.3 million tonnes a year of liquids and condensate, and this can be split into 3.6 million tonnes of liquid natural gas, 1.3 million tonnes of condensate and 400,000 tonnes of liquefied petroleum gas. It uses a massive 50 million litres (11 million gallons) of water every hour to cool the liquid natural gas once it’s on board while its storage capacity is equal to 165 Olympic-size swimming pools.  

Operations Begin….and Stop 

On 26th December 2018, Shell announced that production had commenced on the Prelude FLNG and the first shipment left the facility in July 2019, with another leaving at the beginning of 2020. It appeared as if all was running smoothly. 

But in February 2020, the entire facility was shut down in response to ‘an electrical trip’ according to Shell. Now, I don’t know about you but when I think about an electrical trip I assume a quick flick of the circuit breaker should fix it – but what do I know. 

Shell hasn’t exactly been forthcoming over the exact problems onboard the Prelude FLNG but with time ticking, and costs ballooning, the facility remained out of action. It was later confirmed that it had suffered two incidents that saw the unintended release of gas before the shutdown, which the National Offshore Petroleum Safety and Environmental Management Authority saw serious enough to deem as ‘dangerous’. 

This quickly led to some fevered gossip that perhaps the technology being used by Shell just wasn’t yet up to scratch and perhaps the entire facility would have to be moved back to South Korea for repairs. Shell always strenuously denied this, but as time progressed, it became clear that this wasn’t just a minor issue.  


In January 2021, after nearly a year out of action, the Prelude FLNG once again started production. And as of April 2021, all seems well on the largest floating facility we’ve ever seen. 

But question marks certainly remain, not simply over the facility itself, but with the entire system. Some doubt whether Prelude is even profitable at the moment, and what was seen as the first of many floating platforms may be on hold for the time being. 

To make things even worse for Shell, the price of oil and gas has been falling ever since they commissioned the project and it’s now not clear whether the company will continue building sister facilities to match the Prelude as planned. 

The Prelude FLNG is a colossal piece of engineering that has completely redefined the natural gas industry. But like many large steps in innovation, it has come with countless teething problems. The question now is, are we talking about a quick filling or a major root canal operation?

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