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period. The main types of floating production systems are FPSO
(floating production, storage, and offloading system), FSO
(floating storage and offloading system), and FSU (floating storage
unit).
Tension-leg Platforms, consist of floating rigs tethered to
the seabed in a manner that eliminates most vertical movement of
the structure. TLPS are used in water depths up to about 6,000
feet. The “conventional” TLP is a 4-column design which looks
similar to a semisubmersible. Proprietary versions include the
Seastar and MOSES mini TLPs; they are relatively low cost, used
in water depths between 600 and 3,500 feet. Mini TLPs can also
be used as utility, satellite or early production platforms for larger
deepwater discoveries.
Spar Platforms, moored to the seabed like the TLP, but
whereas the TLP has vertical tension tethers the Spar has more
conventional mooring lines. Spars have been designed in three
configurations: the
"conventional" one-
piece cylindrical hull,
the "truss spar" where
the midsection is
composed of truss
elements connecting
the upper buoyant hull
(called a hard tank)
with the bottom soft
tank containing
permanent ballast, and
the "cell spar" which
is built from multiple
vertical cylinders. The
Spar may be more economical to build for small and medium sized
rigs than the TLP, and has more inherent stability than a TLP since
it has a large counterweight at the bottom and does not depend on

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