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he ASU 4000 design, developed by GVA consultants
and granted ABS approval |
in principle (AIP), promises streamlined module installation,
less motion and greater resistance to structural fatigue during
operation.
AIP certifies that the preliminary engineering is based
upon methods that conform with the ABS Floating Production
Installation (FPI) Guide; Mobile Offshore Drilling Unit (MODU)
Rules; and accepted industry standards for proven technology
and sound engineering practices. AIP facilitates the full
review of the design for classification of the semisubmersible
as an ABS XA1
Floating Offshore Installation.
The asymmetrical design of the unit is intended to reduce
motions of steel catenary risers (SCR). The slanted column
legs curb deck weight, downsizing the unit and making it cost-competitive
with smaller-scale tension leg platforms (TLPs) and spars.
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The column legs connect underwater via rectangular pontoons and
above water via a deck box. The aft pontoon is smaller than the
fore pontoons, and the aft columns are larger than the fore columns.
This altered shape moves the unit’s center of rotation aft,
reducing motions around the pontoons and at the SCR hang-off point.
This configuration provides better vertical motions to the SCR flex
joint and greater flexibility during SCR installation.
Topsides can be installed onshore, allowing easier and less-expensive
hook-up and commissioning. Unlike site-specific TLPs or spars, the
unit can be demobilized in one piece and moved to a new project
site.
The GVA 4000 is targeted for marginal fields in 3,000 feet to
10,000 feet of water. The moored design uses 10- to 12-point semi-taut
combined chain-wire or a taut-leg combined chain-rope system. The
unit can handle 30,000 to 60,000 barrels of oil per day.
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