The world’s largest ship has been launched but developer Royal Dutch Shell already has plans for something bigger.

                              

 The Floating Liquefied Natural Gas (FLNG) plant The Prelude is half a kilometre from bow to stern, room for four football pitches on deck were it not for a clutter of kit towering up to 93m high that will draw gas from under the sea bed for dispatch to Asia by the boatload.

But as the partly-built structure floats out of dry dock for the first time, Shell has said it wants to consolidate its advantage as the first mover in FLNG – an as-yet untried technology for which Prelude will be the flagship.

The oil company's technicians are designing something even larger and tougher than Prelude, a vessel that will need to last 25 years moored in the Indian Ocean's "cyclone alley" off Australia's northwest coast, producing enough gas to supply a city the size of Hong Kong.

"Yes we will move bigger and move into more extreme environments," Bruce Steenson, Shell's general manager of integrated gas programmes and innovation told Reuters last week. "We are designing a larger facility ... That will be the next car off the rails."

Prelude, which analysts says may cost over $12bn (£7.3bn) to build and which is due to be producing by 2017, is a potential game changer for the oil and gas industry as if it is an economic success, gas fields worldwide that are too far out to sea and too small to develop any other way could become viable for LNG production.

Anchored about 125 miles off the Australian coast, Prelude will chill the gas to reduce its volume by a factor of 600 and load it on to specialised LNG tankers.

Prelude will only produce about 3.6 million tonnes a year (mtpa) of LNG along with its 5.3 mtpa of liquids and other hydrocarbons – a fraction of some land-based LNG plants.

But Steenson envisages a bigger version could produce far more – giving it economies of scale closer to those to be enjoyed by bigger land-based producing plants such as Chevron’s Gorgon, a 15.6 mtpa plant taking shape on northwest Australia's coast to tap offshore gas that should be producing in early 2015.

At 600,000 tonnes with its storage tanks full, Prelude will be vast, but it takes up just a quarter of the space a land-based LNG plant of a similar capacity would occupy because components are stacked on top of each other.

LNG plants need access to the ocean anyway so that LNG tankers can load. FLNG eliminates the need for land purchase and reduces environmental objections. With cooling water straight from the ocean and gas tipped piped straight into LNG tankers, there is no need for long seabed pipelines and jetty construction.

Making the first-ever FLNG unit even more of a focus as it takes shape in Samsung Heavy Industries' Geoje shipyard in South Korea, the prototype vessel's most likely first copy model of similar size will now be for the Browse project – another venture for gas off Australia.

Escalating costs forced backers to dump their original, land-based LNG plant plans as its likely cost reached $45bn, and in September this year, they decided to go ahead with Shell's FLNG technology instead.

"The Browse structure will be 90 per cent the same as Prelude," Steenson told Reuters on the sidelines of a conference, citing the "design one, build many" mantra Shell hopes will eventually pay off and placate shareholders worried about the firm's total $45bn-a-year capital spending bill.

Browse's developer, Woodside Petroleum, said in October it may use as many as three of the FLNG vessels Shell is developing along with Samsung Heavy and oil and gas engineers Technip.

An even bigger FLNG plant than the ones to be built for Prelude and Browse could make life more interesting for the competition – a wide range of land-based "wannabe" LNG exporters in Canada, Russia and east Africa, all hoping to tap burgeoning Asian gas demand the same way a number of Australian and US-based LNG developments will over the coming few years.

Location:	Browse Basin, Australia
Depth:	~250 metres
Category:	Floating liquefied natural gas
Interest:	Shell 67.5%, Inpex 17.5%, CPC 5%, Kogas 10%
Fields:	Prelude and potentially other Shell natural gas assets in the region
FLNG facility production capacity:	At least 5.3 million tonnes per annum (mtpa) of liquids: 3.6 mtpa of LNG, 1.3 mtpa of condensate and 0.4 mtpa of LPG
Key contractors:	Technip Samsung Consortium