Focus
Simple, safe —
and cylindrical
Designed as an alternative to conventional ‘ship-shaped’ FPSOs, the Norwegian
company Sevan Marine has designed, developed and is now successfully operating
completely new floating production facilities based on an innovative, patented
cylindrical concept, with automation, control, safety, navigation and telecoms
systems — all supplied by Siemens Oil& Gas Offshore.
While so-called ‘peak oil’ production may
or may not have been passed, it is generally
acknowledged that the boom-times in the
North Sea and other prolific fields have become
a distant memory and ‘easy oil’ is long-gone.
Today, oil companies are being forced to move
to less accessible fields and operate under far
more challenging conditions. This is especially
true for the offshore oil and gas industry,
which has moved increasingly to the development of deepwater reservoirs, while at the
same time tapping smaller fields in shallow
waters. As existing recoverable reserves
continue to dwindle in large fields where
current and mature technologies for drilling
and production have hitherto provided
economically viable solutions, a select number
of specialist companies are now at the forefront of technological development. New and
improved systems are now being employed
which allow a new generation of equipment
suppliers and oilfield operators to exploit
existing marginal fields and ‘stranded’ reserves, as well as to develop new — and frequently
far smaller — discoveries at greater subsea
depths, the ‘final frontier’ for offshore oil and
gas exploration and development.
Floating choice
Among the many new engineering technologies
developed in conjunction with the oil industry
majors, giant floating “ship-shaped” production
and storage vessels have become the system
of choice for the development of an increasing
number of smaller, deepwater oil and gas
fields. These Floating Production, Storage and
Offloading vessels or FPSOs replace the fixed
production platforms and pipeline systems
which produce and export oil and gas from
shallower fields and which are not technically
or commercially viable for smaller, deepwater
applications. FPSOs on the other hand, either
in the form of ship-conversions using existing
hulls, or as new-build vessels, can be towed
out and anchored at the location of the offshore
reservoir to form a ‘hub’ for the producing
wells in the field.
Blowing in the wind
Although current-generation ‘floaters’ provide
a technically sound solution for demanding
deepwater and ultra-deepwater applications,
they include a number of very costly and
technically complex systems, require long
lead-times and are very time-consuming to
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08 Venture December 2008
Focus
build, demanding the specialized facilities of
a major shipyard. The necessary capacity to
build or convert such large vessels limits the
construction of conventional FPSOs to a small
number of yards worldwide. Ironically, the very
fact that most current-generation FPSOs are
conventionally-shaped ships, designed primarily to move through the water efficiently with
least resistance in one direction only, means
that they are less suited to provide a stable
platform. Under the action of waves and wind,
ship-shaped vessels will tend to swing around
their fixed moorings to point into the wind, an
effect known as ‘weathervaning’. For FPSOs
connected to multiple seabed wellheads by
vulnerable and highly critical umbilicals,
including the production risers carrying crude
oil or gas, excessive relative motion could
prove literally catastrophic. To mitigate the
problem, risers are connected through
swiveling couplings to a large and complex
mooring-structure known as a turret, which can
rotate to counter the effects of weathervaning.
The cylindrical solution
In the light of mounting technical and financial
pressures faced by the offshore oil and gas
industry, some eight years ago Sevan Marine
ASA, a leading Norwegian-based engineering
group specializing in building, owning and
operating floating units for offshore applications, took an entirely fresh look at the
requirements for FPSOs. Overcoming many of
the disadvantages in building and operating
a conventional ship-shaped vessel, Sevan’s
innovative solution was designed for maximum
stability with a favorable motion pattern. The
cylindrical deck can accommodate large and
heavyweight process systems and living
quarters, while the space below the deck is used
for oil and ballast tanks. Fabricated in steel,
this simple, modular, symmetrical design
eliminated entirely the need for complicated
and cost-driving turret and swivel systems. The
design-concept together with standard panel
and block fabrication reduced overall complexity significantly and eliminated the need for
very large-scale construction facilities. This in
turn allowed the widest possible choice of
shipyard, resulting in significant savings in
both cost and delivery time. Model testing was
undertaken in 2001, and the contract for the
world’s first cylindrical production and storage
unit, named the FPSO Sevan Piranema, was
signed with Brazil’s oil-giant Petrobras in 2004.
The hull was built at the Yantai Raffles shipyard
in China and towed to Keppel Verolme shipyard,
Rotterdam for outfitting and assembly of the
processing plant and topsides facilities before
being towed out to the Petrobras Piranema
oilfield off the coast of Aracaju in Sergipe, Brazil,
to start commercial oil production in October
2007.
Star performance
Operating in ultra-deep water, starting at
1,000 meters and later to be moved out to
1,600 meters, and carrying up to 25 risers and
umbilicals, this world-first cylindrical FPSO
passed its 12-month production milestone
Mutual relationship: after Sevan’s Piranema and Hummingbird, the Voyageur is the
third such cooperation between Sevan Marine and Siemens Oil & Gas Offshore, with both
partners learning and advancing from project to project.
December 2008 Venture 09
Focus
Busiest place on-board: the Sevan Voyageur’s control room just three weeks before the scheduled
date of sailing.
Siemens automation and control solutions at the heart of the Sevan Voyageur: 6,000 cables, 4,500 I/Os,
and — all in one row — more than 100 meters of switchgear cabinets.
without any major incident, despite weathering
severe storms. Performing far better than even
the most optimistic projections, the use of
standard, service-proven systems and equipment from long-established suppliers including Siemens, has resulted in outstanding
safety and reliability. With a hull diameter of
60 meters and a circular deck covering an area
of 3,220 square meters, the unit has a loaded
draft of 18 meters. Developed specifically for
operation in deepwater fields with relatively
low yields, the Sevan 300 incorporates larger
processing facilities than comparative conventional FPSOs and can handle a larger number
of risers. Together with the ability to take on
very large loads with large deck and storage
areas, this provides a significant improvement
in cost-effectiveness, while hydrodynamic
stability and overall safety are also significantly
enhanced. During its first year of operation the
Sevan Piranema produced 2.9 million barrels
of oil, exported by 14 shuttle tanker cargoes.
electrical power from the on-board generating
plant is fed to medium- and low-voltage networks throughout the vessel through Siemens
transformers and distribution switchgear,
with safety-critical services backed by uninterruptible power supply (UPS) systems. Direct
current supplies for specialized equipment have
also been supplied from the Siemens range,
while all major electric drives are controlled
by Siemens motor control centers. Siemens
Oil & Gas Offshore has also supplied state-ofthe-art automation systems covering process
control and safety systems, including emergency shutdown (ESD) and fire and gas (F&G)
detection and control. Siemens power management and information management systems
have been installed as standard, together with
an on-board simulator for operator training.
In addition, comprehensive telecommunications
equipment from Siemens covers CCTV, video
conferencing and entertainment systems, radio
and satellite communications, telephone,
paging and public address systems, as well as
the FPSO’s navigational aids and general
administration network.
The Siemens connection
Processing up to 30,000 barrels of oil per day,
with a storage capacity of 300,000 barrels and a
gas injection capacity of 3.6 million cubic
meters per day, the Sevan Piranema relies on
Siemens’ systems and equipment to control all
vital operations. The 3.75 megawatts (MW) of
10 Venture December 2008
Four — and counting
Following the first FPSO contract for Petrobras,
Sevan Marine has been awarded four more
contracts for same-size units. Already in
successful production since September 2008,
the FPSO Sevan Hummingbird is the first unit
of this kind operating on Venture Production's
Chestnut field in the harsh UK Central North
Sea. In Fsebruary 2007, Oilexco North Sea Ltd.
awarded Sevan a letter of intent for the third
Sevan 300; at the time of writing, the unit is
ready for tow out and installation at the Shelley
field, also in the Central North Sea. Following
these three first units, another two hulls are
under construction in China, and a second
contract from Venture Production is signed for
one of these Sevan 300s.
Extending the concept
Although the cylindrical design for floating
storage and production vessels is not unique
to Sevan Marine, the company’s symmetrical,
modular, highly-standardized approach
coupled with conventional panel and block
steel fabrication methods has provided an
industry benchmark. Nevertheless, the company is now extending its patented concept
with the addition of an ultra-deepwater drilling
facility. The first of this new generation of
Floating Drilling, Processing, Storage and
Offloading vessels, the Sevan Driller FDPSO is
currently under construction at Cosco’s
Nantong shipyard in China. Designed to
include the most advanced capabilities in the
Focus
“Simple and safe — that’s the beauty of Sevan’s
concept.” Erskine Rozario, Sevan Marine’s site
manager.
industry and with the highest environmental
and safety standards, it will be capable of
drilling wells to more than 12,000 meters in
water depths in excess of 3,800 meters, and
will have a storage capacity of up to 150,000
barrels of oil. On completion the vessel will
be will be entering into a 6 year drilling for
Petrobras operation in ultra-deep Brazilian
waters.
Forward in partnership
As well as extending its world-beating cylindrical-hulled FPSO design to include drilling,
Sevan Marine is looking to use the concept for
a range of other offshore applications. These
include subsea installation and construction,
LNG and LPG gas treatment and as a mobile
service and accommodation platform. Plans
also include the construction of latest-technology ‘gas-to-wire’ power generating installations
with carbon capture and storage capability,
exporting bulk electricity to shore. Described
by Sevan Marine as “the obvious choice” as
a single one-stop-shop supplier, Siemens has
forged a long-term relationship with the
offshore company, working in partnership
through mutual and ongoing trust and collaboration for what is clearly a bright future; for
Sevan’s patented ‘simple, safe — and cylindrical’
concept.
December 2008 Venture 11
Monitor
New horizons for
compression technology
Combining eco-friendly energy efficiency with operational flexibility,
Siemens has developed a completely new range of turbocompressors
designed specifically to match the requirements for the latest steamturbine-driven air separation systems.
The past decade has seen an accelerating
trend in thermal-based industrial processes
towards the capture of ‘waste’ heat, using
thermal energy to generate additional steam,
raising overall thermal efficiency, reducing
fuel consumption and cutting atmospheric
emissions. A significant and increasing number
of these heat-producing ‘exothermic’ processes
incorporate integrated air-separation systems
to provide the very large volumes of highpurity oxygen on which they are all based. These
processes include coal-to-liquids (CTL) and
gas-to-liquids (GTL) conversion technologies as
well as power generation using the integrated
gasification combined cycle (IGCC) process.
Other applications encompass a range of industrial processes including steelmaking, while
12 Venture December 2008
the advance of ‘cleaner coal’ power-generation
systems, including the latest carbon capture
and storage (CCS) technologies, are creating
future new markets. The large majority of the
air-separation systems used in these applications employ the cryogenic distillation process,
which relies on the differences in boiling
points of gases to separate and purify them.
Cool compressors
Essentially a large-scale refrigeration system,
the single most important element in a
cryogenic air-separation plant is the compressor.
In typical operation, filtered air is fed to a
multi-stage compressor train, and contaminants
including carbon dioxide and water vapor are
removed. The compressed air is expanded and