Business management of projects in the design, engineering, procurement, fabrication and installation of spar floating facilities, namely, deep draft, caisson type vessel that provides a platform for people and/or equipment to work offshore in deep water, for use in oil, gas, and mineral exploration, extraction, processing, transportation and storage.
Design, engineering, and procurement, construction, installation, and repair of all spar floating facility systems, namely, deep draft, caisson type vessel that provides a platform for people and/or equipment to work offshore in deep water, and subsystems, namely, hulls, mooring, production risers, drilling risers, import and export risers and pipelines, and drilling and/or production topside; and economic and financial evaluation of spar and spar-related facilities.
The first Spars were based on
the Classic design. This evolved into the Truss Spar by replacing
the lower section of the caisson hull with a truss. Spars are
often considered along with TLPs for dry tree solutions because
they offer small vertical motion. However, Spars are different
from both Semis and TLPs in the mechanism of motion control.
One of the distinctions of the Spar is that its center of gravity
is always lower than the center of buoyancy which guarantees
a positive GM. This makes the Spar unconditionally stable.
The Spar derives no stability from its mooring system, so it
does not list or capsize even when completely disconnected
from its mooring.
The deep draft is a favorable attribute for minimal heave
motions. Its deep draft and large inertia filter wave frequency
motions in all but the larger storms. The natural period in
heave and pitch are above the range of wave energy periods.
The long response periods for Spars mitigate the mooring and
riser dynamic responses, which are common to ship shaped FPSOs
and Semis. The deep draft, along with protected centerwell,
significantly reduce the current and wave loading on the riser
system These loads normally control the tension and fatigue
requirements of the production risers on TLP or Semis
One of the principal advantages of the Spar over other floating
platforms lies in its reduced heave and pitch motions. Low
motions in these degrees of freedom permit the use of dry trees.
Dry trees offer direct vertical access to the wells from the
deck, which allows the Spar to be configured for full drilling,
workover, production processing, or any combination of these
Truss Spar Concept
Truss Spar is divided into three distinct sections. The cylindrical
upper section, called the “hard tank,” provides
most of the in-place buoyancy for the Spar. The middle truss
section supports the heave plates and provides separation between
the keel tank and hard tank. The keel tank, also known as the “soft
tank,” contains the fixed ballast and acts as a natural
hang-off location for export pipelines and flowlines since
the environmental influences from waves and currents and associated
responses are less pronounced there than nearer the water line.
the original designs, the Hard Tank architecture is the same
in the Classic and Truss Spar designs FloaTEC, LLC has
recently developed a Ring Spar architecture for the Hard Tank.
This architecture offers a more fabrication-friendly option
with reduced fabrication costs. Horizontal decks and radial
bulkheads divide the hard tank spaces into tanks and voids.
The lower set of tanks is configured to contain seawater ballast,
which can be increased, decreased, or moved between tanks to
correct for major changes in topsides weight, topsides eccentricity,
SCR weight, or hull flooding resulting from damage. A
ring of additional voids is provided at the waterline area.
These are used during topsides installation and prior to TTR
The trussed mid-section of the hull is
an X-braced space frame constructed of tubular members and
flat plates called “heave
plates.” The heave plates increase the added mass in
the vertical direction and thereby increase the natural heave
period of the Spar and bringing it above the range of periods
in the wave energy. In a Truss Spar, they also increase
The third section of the hull is the “keel tank,” which
is attached to the bottom of the truss at the keel. It
provides the buoyancy while the Spar is wet-towed horizontally
to site for installation. The keel tank is flooded to initiate
upending and, finally, receives the field-installed, fixed
ballast, which is key to the Spar’s unmatched stability. The
porches for the steel catenary export pipeline risers are on
the perimeter of the keel tank.
The Spar hull includes two access shafts. These shafts contain
the ballast and utility piping and instrumentation. They also
allow direct personnel access to the piping and to every void
tank without requiring workers to pass through an intermediate
compartment. Only one void need be open at a time. Access shafts
are painted, lighted, and vented, as required, for entry.
The seawater ballast system has a dedicated
centrifugal pump at the bottom of each access shaft for discharging
ballast water. Ballast water is supplied to the tanks from
the utility seawater manifold. Each seawater ballast discharge
pump services the same two ballast tanks served by its access
shaft. All ballasting is over the top of the hull, so that
ballast tanks have to be intentionally filled by the ballast
eliminates the possibility of inadvertent flooding, which can
occur if a sea-chest system is used.
Copyright © FloaTEC, LLC 2010