The Biggest Ship in the World Might Not Even Be a Ship

The Shell Prelude Courtesy Shell Global

Five months ago, when the Maersk Mc-Kinney Møller embarked on its maiden voyage, the 400-meter-long vessel was the largest ship in the world. That title is already under assault.

An even bigger ship floated out of dry dock on Wednesday from a shipyard on the other side of the South Korean island where Maersk’s gigantic Triple-E models are being built. The new record-holder is the Shell Prelude, a vessel measuring 488 meters (1,601 feet) from end to end. At that size, it’s not only the biggest ship in the world, it’s the biggest ever built—longer even than the Seawise Giant, a supertanker built in the late 1970s and scrapped three years ago.

That is, if you call the Prelude a ship: Shell‘s vessel can’t move under its own steam and will spend the vast majority of its lifetime anchored in place. It’s not even complete yet; the float-out is a key stage in its production. The hull still has to be fitted with a maze of machinery, and the whole is not due to be finished until 2017. Shell isn’t releasing cost figures, but Reuters cited analyst estimates ranging from $10.8 to $12.6 billion.

What is the point of a $10-billion, 1,600-foot-long floating island? The Prelude is the first of a new class of vessel called a floating liquefied natural gas (FLNG) platform. Natural gas, unlike petroleum, has to be turned from gas to liquid form to be transported, which in the past has meant that natural gas extracted from beneath the ocean floor had to be piped to massive facilities onshore. But the low-hanging fruit of natural gas fields are exhausted, even as the world’s appetite for natural gas continues to grow, so energy companies such as Shell are pushing to exploit gas fields that are far from shore or off the coast of countries plagued by political instability.

FLNG vessels are an attempt to solve that problem. Once completed, the Prelude can be anchored directly over a gas field. Gas will be pumped up into it to be processed, liquefied, stored, and eventually transferred to tankers that take it to market. Once completed, the Prelude will be towed to a spot in the ocean 125 miles off the northwestern coast of Australia, a gas field that up until now has been impractical to develop.

The engineering challenges are formidable. The spot the Prelude will call home for what Shell estimates will be 20 to 25 years lies in the middle of the Indian Ocean’s “cyclone alley,” so the vessel had to be built to survive a category-5 cyclone. Part of its stability comes from sheer size, but the structure also relies on some clever design. The platform will be affixed to the sea floor by four groups of mooring lines that will attach to a 93-meter-high turret, around which the rest of the platform can rotate in accordance with prevailing winds and currents, like a weather vane that’s a third of a mile long.

One of the biggest design difficulties was to fit all the required equipment onto the ship. The Prelude is a fraction of the size of an onshore LNG facility. In other words, gargantuan though it may be, the biggest challenge for those creating the vessel was getting it to be as small as it is.

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