Huge gas vessel a prelude to bigger things

It will be the biggest thing ever sent to sea - but as the Prelude FLNG vessel was launched on Tuesday, plans were already under way for something bigger.

With a bow and stern half a kilometre apart, four football pitches would fit on Prelude's deck were it not for a clutter of kit towering up to 93 metres high that will draw gas from under the seabed for dispatch to Asia by the boatload.

Now, as the partly-built structure floats out of dry dock for the first time, developer Royal Dutch Shell wants to consolidate its advantage as the first mover in floating liquefied natural gas (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 said last week. "We are designing a larger facility … that will be the next car off the rails."

Prelude, which analysts say may cost over US$12 billion to build and which is due to be producing by 2017, is a potential game changer for the oil and gas industry.

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.