DNV INNOVatION PrOjeCt 2012 oil and gas industry
OPera OFFSHOre POWer SYSteM FOr tHe NeW era
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DNV INNOVATION PROJECT 2012 as oil and gas companies extend their presence to remote and ultra-deep waters, one of their main challenges is to maintain environmentally responsible operations while maximising returns on investments. DNV is proposing a way of significantly reducing emissions and improving profits through the use of a shared power source.
DNV has launched a concept for oil and gas companies •• to maintain environmentally responsible operations while maximising return on investment •
CONTENTS
Challenges 4 • OPera concept 6 • Main benefits • Key features 1412 •
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•• the challenges Platforms are typically fitted with large and heavy power generation equipment designed to ensure redundant capacity to meet the high availability requirements. However, these generators are often operated at part load, leading to high emissions.
Challenges the OPera concept Main benefits Key features
COMBINING RESPONSIBLE AND PROFITABLE OPERATIONS As oil and gas companies extend their presence to remote and ultra-deep waters, one of their main challenges is to maintain environmentally responsible operations while maximising returns on investments. The high electric power demands offshore lead to environmental concerns and trigger a quest for alternative power supplies. DNV has devised an alternative power supply concept, OPera, to meet demand for increased power offshore.
HIGH OFFSHORE EMISSIONS At present, to meet the offshore power demand, conventional FPSOs are fitted with substantial power generation equipment. The power arrangement typically consists of four gas turbine units, one used at full capacity, and the remaining throttled to meet the varying demand or otherwise reserved for redundancy. This redundant capacity is necessary to meet the high availability requirements of each independent vessel. However, operating gas turbines at low efficiency results in high fuel consumption and elevated emissions.
SPACE-CONSTRAINED FPSOS INCREASING OFFSHORE POWER DEMAND Large and remote fields in ultra-deep waters typically utilise FPSOs that may require more than 100 MW of capacity. The introduction of offshore LNG production will increase topsides’ energy needs. Furthermore, the increasing use of subsea processing is driving power consumption trends significantly. DNV is working closely with the industry to qualify technology and develop key standards for subsea power.
As large-throughput FPSOs typically have deck areas crowded with equipment for water injection and gas processing, available space becomes an issue. This raises concerns related to available lay-down and maintenance areas and room for tie-ins of future fields. DNV is therefore proposing a way of significantly reducing emissions and improving returns on investment in a cluster of field developments, through the use of a shared energy source, freeing deck space on connected platforms. The result is DNV OPera, the Offshore Power system for the new era.
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•• the OPera concept OPera consists of a floating power hub and an electrical distribution system, supplying power to a network of offshore installations
Challenges the OPera concept Main benefits Key features
SHARED POWER SUPPLY
RELIABLE POWER SYSTEM
The OPera concept addresses the power demand of several connected installations through the introduction of submarine cables and centralized power generation.
Based on power system analysis, DNV has dimensioned a robust system to supply electricity to connected installations.
HIGHLY EFFICIENT POWER GENERATION The 700 MW power plant recovers exhaust heat from seven gas turbines to drive a second cycle of three steam turbines, both cycles spinning electric generators. This combined cycle configuration increases power generation efficiency by approximately 16 per cent, compared with conventional gas turbines alone. Together with consolidation of power generation, allowing equipment to run at optimal load, the result is a significant overall reduction in emissions. Depending on water depth, different hull designs can support the power plant. To accommodate the power equipment in ultra-deep water scenarios, a semi-submersible platform is the ideal configuration.This platform is connected directly to a gas export pipeline through a riser, providing a reliable supply of fuel. Where no pipeline infrastructure exists it could receive gas directly from the producing installations.
Transformers step up the voltage before the power is distributed using 132 kV AC power cables. To ensure supply reliability, the installations are connected in a closed loop configuration, providing redundant connections. The OPera concept utilises next generation dynamic power cables for ultra-deep waters. DNV is heavily involved with the industry, maturing cable design to overcome the challenges of tensile loads, dynamic response, fatigue and installation of submarine cables.
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•• The 700 MW combined cycle power plant.
•• Semi-submersible platform for the ultra-deep water scenario.
•• Transformers step up the voltage before the power is distributed using 132 kV AC power cables.
Challenges the OPera concept Main benefits Key features
•• the increasing use of subsea processing is driving power consumption trends.
•• the OPera concept
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•• With its centralized location, OPera allows improvements in operational logistics.
•• The OPera power hub can be designed in different variants to meet specific needs.
•• T o ensure supply reliability, the installations are connected in a closed loop configuration.
Challenges the OPera concept Main benefits Key features
•• OPera increases available deck space on connected platforms, through the elimination of power generation equipment dedicated to oil and gas processing.
•• DNV is heavily involved with the industry, maturing dynamic cable designs.
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•• main benefits With OPera, DNV’s innovative concept for networking offshore installations, oil and gas companies will now be able to foresee a future of reduced emissions and improved profits.
Challenges the OPera concept Main benefits Key features
REDUCED EMISSIONS AND INCREASED REVENUE OPera is an economically sound concept that reduces emissions and permits additional revenue from natural gas sales through the reduction of gas consumption offshore. Additionally, it provides the potential for increased oil production and improved design of connected platforms.
MORE DECK SPACE AVAILABLE OPera provides several potential benefits for the connected FPSOs. It increases available deck space through the elimination of power generation equipment dedicated to oil and gas processing. Significant increases in revenue could therefore be achieved with the installation of additional processing capabilities, resulting in more oil production from the same size FPSO. Available deck space is especially valuable for large-throughput FPSOs, which are typically crowded with water injection and gas processing equipment. Freed area can be used for the installation of redundant processing equipment, additional lay-down and maintenance areas, and for tie-ins of future fields. Increased spacing of modules may also provide for improved overall safety. Another option is smaller, less costly FPSOs with shorter lead times.
•• available deck space can be used to add oil processing equipment.
IMPROVED LOGISTICS With its centralized location, OPera allows improvements in operational logistics, by consolidating the location of power generation personnel, maintenance and spare parts. Other benefits include reduced noise on each FPSO, making for a better working environment.
TAILORED TO SPECIFIC NEEDS The OPera power hub can be designed in different variants, such as a logistical hub, a centralized CO2 removal unit, or part of offshore LNG production.
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•• key features •• additional revenue from natural gas sales through the reduction of gas consumption offshore.
•• Freeing up valuable deck space on connected platforms, for increased oil production, higher redundancy, improved safety, future tie-ins or other value creating use.
•• reduced need for backup power capacity.
•• Can be tailored to specific needs.
•• 700 MW combined cycle power plant. •• 132 kV submarine cables in closed loop configuration provides redundant connections.
Challenges the OPera concept Main benefits Key features •• Improved operational logistics.
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Š Det Norske Veritas AS. Design and layout: Coor Media 1202-067. Animations p 6, 8-12, 14: Designimations. Print: Coor Media. Photo: Cover: Getty Images/ Wolcott Henry, p 2: Getty Images/Paul Avis, p 4: DNV/Knut Vadseth