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6.3. SPAR platforms

A SPAR, named for logs used as buoys in shipping and moored in place

vertically, is a type of floating oil platform typically used in very deep waters. Spar

production platforms have been developed as an alternative to conventional

platforms. A Spar platform (fig. 6.27) consists of a large-diameter, single vertical

cylinder supporting a deck. It contains a deep-draft floating caisson, which is a

hollow cylindrical structure similar to a very large buoy. Its four major systems are
hull, moorings, topsides and risers. About 90% of the structure is underwater. The

spar design is now being used for drilling, production, or both. The distinguishing
feature of a spar is its deep-draft hull, which produces very favorable motion

characteristics compared to other floating concepts. Water depth capability has
been stated by industry as ranging up to 10,000 ft. The first Spar platform was

installed in September of 1996. It follows the concept of a large diameter single

vertical cylinder supporting deck. These are a very new and emerging concept: the

first spar platform, Neptune, was installed off the USA coast in 1997. Spar

platforms have taut catenary moorings and deep draught, hence heave natural

period is about 30 seconds.

Presently there are 17 SPARs in operation (fig. 6.28):

▫ 3 Classic SPARs;

▫ 13 Truss SPARs;

▫ 1 Cell SPAR.

The different SPAR designs (tab. 6.1) reflect industry innovations

Each design (fig.6.29) is an improvement on an older model and offers

improved functionality at a reduced cost.

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