Shell’s Massive FLNG Turret Module Ships Out

By Valerie Wilke 27 Aug 2014

The largest piece of the turret for Shell’s Prelude floating liquefied natural gas (FLNG) facility has set sail from Dubai and is making its way to South Korea. 

Weighing in at 4,300 tons, turret modules 1 and 2 are heading to the Samsung Heavy Industries shipyard in Geoje, South Korea, where the FLNG facility is under construction.

The turret was designed by turret pioneers SBM Offshore in Monaco, and Dubai’s Drydocks World, an international service provider to the shipping, maritime, offshore, oil, gas and energy sectors, began building the turret in 2012. Once all six turret modules are integrated in South Korea and transported to Australia, they will comprise the largest turret mooring system in the world, weighing more than 11,000 tons.

“The turret is an example of the truly global nature of this project,” said Matthias Bichsel, Shell Projects and Technology Director. 

At nearly 100 meters, the turret will be taller than Big Ben and spacious enough to house the Arc de Triomphe, making it the largest turret ever constructed. In its completed state, Shell says the Prelude FLNG will be the largest structure ever sent to sea, displacing as much water as a fleet of six aircraft carriers, and will produce at least 3.6 million tons of liquefied natural gas (LNG) per year. The facility will be 488 meters long and 74 meters wide, and will weigh more than 600,000 tons with the cargo tanks full.

The turret—which unites the subsea connections that extract and control the flow of gas from the reservoir—is part of a mooring system designed to ensure Prelude FLNG can operate safely in extreme weather conditions, such as Category 5 cyclones. The turret’s swivel design enables the facility to mimic the moves of a weather vane, allowing the hull of the facility to rotate according to the prevailing wind, waves, or current, while the turret moorings remain secured to the sea floor.  

The mooring system—a combination of chains and wire—includes four groups of four mooring lines that will secure the facility to anchor points about 250 m below the sea surface. These connect the turret mooring system to the anchor piles, each 62.5 m long and 5.5 m in diameter, secured to the seabed. Extensive testing programs and weather simulations were conducted of the FLNG design to assess its ability to remain connected and moored to the sea floor.

Once complete, Prelude FLNG will operate in a remote basin around 200 km off Australia’s northwest coast for around 25 years. The Prelude FLNG facility will produce at least 5.3 million tons per annum (MTPA) of liquids; 3.6 MTPA of LNG, enough to meet Hong Kong’s annual natural gas needs; 0.4 MTPA of liquefied petroleum gas; and 1.3 MTPA of condensate (equivalent to 35,000 bbl/d). After the first 25-year assignment, the Prelude FLNG may be refurbished and moved to a different field for another quarter century.

The facility will allow Shell to produce natural gas at sea, cool it onboard into LNG, and pump it directly into ships that will transport it to customers internationally. Shell it expects Prelude to be the first of many FLNG facilities.

“It’s great to see our innovative designs and technologies become a reality as we reach significant project milestones like this,” Bichsel said.

Shell is the operator of Prelude FLNG in a joint venture with INPEX (17.5%), Korea Gas Corporation (10%), and the Overseas Private Investment Corporation (5%), along with long-term strategic partners Technip and Samsung Heavy Industries (the Technip Samsung Consortium). The project will be the first to use Shell’s FLNG technology, which allows for natural gas to be extracted, processed, stored and transferred at sea. FLNG eliminates the necessity for pipelines to shore, dredging, and onshore works, reduces development costs, and limits the disturbance to the surrounding environment. 

Valerie Wilke is a Web Content Associate Editor for SPE.

Further Reading

OTC-20513: FLNG Design Issues—Building on Known Technology, Conn Fagan (Det Norske Veritas), Hans Olav Sele, Tom Klungseth Oestvold (DNV)
SPE-156178: Prelude FLNG Development Environmental Footprint and Conditions of Approval in a Post Montara and Macondo World, Brian Cohen, Ma. Filipina Dumayas Caymo (Shell Philippines Explor. B.V.)
SPE-165855: FLNG Lean—A Natural Development, Marc van Dongen (Shell), Harry van der Velde (Shell)