An onshore LNG plant normally spreads across hundreds of hectares — storage tanks, liquefaction trains, jetties, pipelines. Prelude compresses the same functions onto a single hull, 488 m long, moored permanently at the gas field itself.

Fully loaded, it displaces around 600,000 tonnes — roughly five to six times the displacement of a Nimitz-class aircraft carrier — making Prelude the largest floating structure ever constructed, built with more than 260,000 tonnes of steel.

488 m
Hull length
74 m
Hull width
≈600,000 t
Fully loaded displacement
260,000+ t
Steel used in construction
Phase 1 — Hull construction and launch
Longer than four football fields, before topsides
The Technip Samsung Consortium (TSC) — a joint venture between Technip and Samsung Heavy Industries — built the hull at Samsung's Geoje Island shipyard in South Korea, laying it down in October 2012 and floating it out of dry dock in December 2013.
Phase 2 — Topside module integration
Modules heavier than most complete platforms
Topside modules — reported in the tens of thousands of tonnes, heavier collectively than many complete offshore platforms built elsewhere — were lifted and integrated onto the hull at Geoje after it launched in November 2013 with no superstructure at all. Compressing an entire onshore LNG plant's processing, liquefaction, storage, and offloading equipment into modules of this scale took engineers a cumulative 1.6 million working hours to solve.
Phase 3 — The turret mooring system, built on another continent
100 metres, 11,000-plus tonnes, fabricated in Dubai
Prelude's mooring turret — the world's largest of its kind at nearly 100 m in height, with a completed weight reported in excess of 11,000 tonnes — was subcontracted to a separate yard, Drydocks World Dubai, and built in five sections, the largest of which alone weighed 4,300 tonnes, before being shipped roughly 6,500 km to Geoje for integration with the hull. A structure of that scale, built on a different continent from the vessel it would eventually anchor, turned logistics coordination into as much of an engineering problem as the lift itself.
Phase 4 — The long tow to the field
Moving the world's largest floating object to its final position
Once construction was substantially complete, Prelude was towed from South Korea to the Browse Basin, roughly 475 km offshore of Broome, Western Australia — moving the largest floating structure ever built across open ocean to a field it would then never leave.
Phase 5 — Permanent mooring
Holding position through category five cyclones
At its final location, in roughly 250 m of water, Prelude is held in place by four groups of mooring chains anchored to suction piles embedded in the seabed — a mooring system engineered to keep the facility on station through category five cyclones for a planned 25-year field life before overhaul.

Topside modules heavier than most complete platforms, a mooring turret built on another continent and shipped 6,500 kilometres for integration — an entire onshore LNG plant assembled from pieces too large to move any other way.

Prelude FLNG stands as a reference case for offshore energy infrastructure at the extreme end of scale: not a platform bolted to the seabed, but a fully self-contained processing plant built to float, moor, and operate for decades at a single field location, deploying Shell's floating LNG technology for the first time anywhere in the world.

For further reading on offshore heavy lift and marine construction, see What is Heavy Lift Engineering?

Related case studies: Mahlsdorf Wind Farm · Baihetan Dam · China Offshore Converter Station

Sources: Offshore Energy — the 4,300-tonne largest turret section leaving Drydocks World Dubai; The Maritime Executive — the completed turret at nearly 100 m high and over 11,000 tonnes; Ship Technology — hull dimensions and topside description. Published sources differ on whether reported topside weights describe individual modules or the topsides as a whole, so this case study describes them qualitatively rather than assigning a disputed figure.

Frequently Asked Questions

Prelude FLNG measures 488 m long and 74 m wide, built with more than 260,000 tonnes of steel. Fully loaded, it displaces around 600,000 tonnes of water — roughly five to six times the displacement of a Nimitz-class aircraft carrier — making it the largest floating structure ever constructed.

Prelude was designed and constructed by the Technip Samsung Consortium (TSC), a joint venture between Technip and Samsung Heavy Industries, at Samsung's shipyard on Geoje Island, South Korea. The hull was laid down in October 2012 and launched from dry dock in December 2013.

Prelude processes, liquefies, stores, and transfers gas directly at the offshore field, using onboard equipment miniaturised from a full-scale onshore LNG plant. Ocean-going LNG carriers can offload the liquefied gas directly from the facility, eliminating the need to pipe gas to a land-based processing plant.

Prelude's mooring turret — the world's largest of its kind at nearly 100 m tall, with a completed weight reported in excess of 11,000 tonnes — was subcontracted to Drydocks World Dubai and built in five sections, the largest of which alone weighed 4,300 tonnes, before being shipped roughly 6,500 km to the Geoje shipyard in South Korea for integration with the hull.

Prelude is moored at a water depth of roughly 250 m in the Browse Basin off Western Australia, using four groups of mooring chains anchored by suction piles embedded in the seabed. The mooring system is designed to hold the facility in place even through category five cyclones.