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New skyscraper-sized gas plant is the biggest thing on the waves

Updated 11:12 AM ET, Thu December 12, 2013
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Longer than the Empire State Building is tall and more than six times heavier than the largest aircraft carrier when full, Shell's Prelude FLNG (Floating Liquefied Natural Gas) facility will become one of the world's largest floating objects when completed (expected to be in 2017).

The 488-meter-long and 74-meter-wide structure is currently being assembled at Samsung's Geoje Island ship yard in South Korea and tentatively took to the water for the first time last week.

Once building work is complete, the giant structure will be towed to a carefully selected spot roughly 125 miles off the northern Australian coast where it will extract and process gas from deep beneath the ocean surface.
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Prelude will operate in deep-water fields that have previously been considered too costly or difficult to develop. Gas will be extracted from beneath the ocean floor before being piped up to the surface where facilities on board will chill the gas to -162° Celsius (-260°F), turning it into liquid and shrinking its volume by 600 times.

This liquified gas will then be transferred to ocean tankers before being transported directly to towns and cities around the world.
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A major advantage of a floating facility is that processing and production will essentially have taken place at sea.

This means the miles of pipes that would have carried the gas to shore, as well as all the complex infrastructure that goes with building a processing plant on land, will not be required.
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Despite its hefty proportions, Prelude is only one-quarter the size of an equivalent facility on land. Engineers have designed components that will stack vertically to save space. The operating plant, for example, will be placed above LNG storage tanks.

An assembly of eight one-metre diameter pipes, meanwhile, will extend from Prelude to roughly 150 meters below the ocean's surface, helping to deliver around 50,000 m3 (cubic meters) of cold seawater each hour. This will help cool the gas and ensure that extra space for cooling equipment on deck is not required.
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More that 600 engineers have worked over 1.6 million man hours working on the design options for the Prelude FLNG Project.

In October this year, the Daily Telegraph reported Royal Dutch Shell CEO, Peter Vosser, expected more FNLG facilities to be built in the years to come. The UK paper also stated that Malaysia's Petronas had begun building a smaller FLNG plant, which could become operational before Shell's, and that US giant ExxonMobil is planning a project even bigger than Shell's.
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One of the biggest challenges of FNLG facilities will be ensuring they can withstand the often rough and unpredictable weather conditions experienced far out at sea.

Shell say Prelude will be able to withstand high winds, giant waves and the strongest cyclones thanks to its sheer scale and one of the largest mooring systems in the world. A 93-metre (305-foot) high turret, spacious enough to house the Arc de Triomphe, runs through the facility and will be anchored to the seafloor by four groups of mooring lines.
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Prelude's storage tanks will be based below its vast deck and are capable of storing up to 220,000 m3 of LNG (liquified natural gas), 90,000 m3 of LPG (liquified petroleum gas), and 126,000 m3 of condensate (the hydrocarbons produced after a gaseous substance is transformed into a liquid).

This total storage capacity is equivalent to around 175 Olympic swimming pools, Shell estimates. The company also ventures that the gas produced at the Prelude field alone in one year could cater for 117% of Hong Kong's annual energy needs.
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