Spar (platform)

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Devil's Tower Spar Platform

A spar is a type of floating oil platform typically used in very deep waters, and is named for logs used as buoys in shipping that are moored in place vertically. Spar production platforms have been developed as an alternative to conventional platforms.[1]

A spar platform consists of a large-diameter, single vertical cylinder supporting a deck. The cylinder is weighted at the bottom by a chamber filled with a material that is denser than water to lower the center of gravity of the platform and provide stability.[2] Spars are anchored to the seabed by way of a spread mooring system with either a chain-wire-chain or chain-polyester-chain composition.[3]

There are three primary types of spars; the classic spar, truss spar, and cell spar. The classic spar consists of the cylindrical hull noted above, with the heavy ballast at the bottom of the cylinder.

A truss spar has a shorter cylindrical "hard tank" than a classic spar and has a truss structure connected to the bottom of hard tank. At the bottom of the truss structure, there is a relatively small, square shaped "soft tank" that houses the heavy ballasting material. The majority of spars are of this type.[4]

A cell spar has a large central cylinder surrounded by smaller cylinders of alternating lengths. At the bottom of the longer cylinders is the soft tank housing the heavy ballasting material, similar to a truss spar. There is currently only one cell spar in operation.[5]

The Brent Spar, a platform designed for storage and offloading of crude oil products was installed in the Brent Field in June of 1976. The attempted deep sea disposal of the platform in the 1990s created a huge backlash by Greenpeace. The Spar was eventually dismantled and pieces were used as a foundation for a quay in Norway.[6]

The first spar designed for oil and gas production was the Neptune spar, located in the Gulf of Mexico and was installed in September 1996 by Kerr McGee (now Anadarko).[7]

The world's deepest production platform is Perdido, a truss spar in the Gulf of Mexico, with a mean water depth of 2,438 meters. It is operated by Royal Dutch Shell and was built at a cost of $3 billion.[8]

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