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December 2008 Venture 07

Simple, safe — and cylindricalDesigned 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 develop-ment 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 fore-front 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’ reser-ves, 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 choiceAmong 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 windAlthough 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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December 2008 Venture 09

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.

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 prima-rily 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 solutionIn 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 applica-tions, 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 complex-ity 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 performanceOperating 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

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Busiest place on-board: the Sevan Voyageur’s con-trol 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 equip-ment from long-established suppliers inclu-ding 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 conven-tional 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.

The Siemens connectionProcessing 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

electrical power from the on-board generating plant is fed to medium- and low-voltage net- works throughout the vessel through Siemens transformers and distribution switchgear, with safety-critical services backed by uninter-ruptible 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-of-the-art automation systems covering process control and safety systems, including emergen-cy shutdown (ESD) and fire and gas (F&G) detection and control. Siemens power manage-ment 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.

Four — and countingFollowing 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 conceptAlthough 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 compa-ny 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

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“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 partnershipAs well as extending its world-beating cylindri-cal-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-techno-logy ‘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 collabo-ration for what is clearly a bright future; for Sevan’s patented ‘simple, safe — and cylindrical’ concept.

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 steam-turbine-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 high- purity 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 indus-trial processes including steelmaking, while

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 applica-tions employ the cryogenic distillation process, which relies on the differences in boiling points of gases to separate and purify them.

Cool compressorsEssentially 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

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