OFFSHOre POWer SYSteM FOr tHe NeW era

DNV INNOVatION PrOjeCt 2012oil and gas industry

OPera

•• DNV has launched a concept for oil and gas companies to maintain environmentally responsible operations while maximising return on investment •

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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 environmen-tally 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.

Challenges 4 OPera concept 6Main benefits 12Key features 14

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CONTENTS

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.

•• the challenges

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COMBINING RESPONSIBLE AND PROFITABLE OPERATIONSAs 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.

INCREASING OFFSHORE POWER DEMANDLarge and remote fields in ultra-deep waters typi-cally 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.

HIGH OFFSHORE EMISSIONSAt present, to meet the offshore power demand, conventional FPSOs are fitted with substantial power generation equipment. The power arrange-ment 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 neces-sary to meet the high availability requirements of each independent vessel. However, operating gas turbines at low efficiency results in high fuel con-sumption and elevated emissions.

SPACE-CONSTRAINED FPSOSAs 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.

Challengesthe OPera concept

Main benefitsKey features

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OPera consists of a floating power hub and an electrical distribution system, supplying power to a network of offshore installations

•• the OPera concept

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SHARED POWER SUPPLYThe OPera concept addresses the power demand of several connected installations through the introduction of submarine cables and centralized power generation.

HIGHLY EFFICIENT POWER GENERATIONThe 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 approxi-mately 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 configu-ration.This platform is connected directly to a gas export pipeline through a riser, providing a reli-able supply of fuel. Where no pipeline infrastruc-ture exists it could receive gas directly from the producing installations.

RELIABLE POWER SYSTEMBased on power system analysis, DNV has dimensioned a robust system to supply electricity to connected installations.

Transformers step up the voltage before the power is distributed using 132 kV AC power cables. To ensure supply reliability, the installa-tions are connected in a closed loop configura-tion, 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.

Challengesthe OPera concept

Main benefitsKey features

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•• transformers step up the voltage before the power is distributed using 132 kV aC power cables.

•• the 700 MW combined cycle power plant.

•• Semi-submersible platform for the ultra-deep water scenario.

Challengesthe OPera concept

Main benefitsKey features

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•• the OPera concept

•• the increasing use of subsea processing is driving power consumption trends.

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•• to ensure supply reliability, the installa tions are connected in a closed loop configura tion.

•• the OPera power hub can be designed in different variants to meet specific needs.

•• With its centralized location, OPera allows improvements in operational logistics.

Challengesthe OPera concept

Main benefitsKey features

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•• DNV is heavily involved with the industry, maturing dynamic cable designs.

•• OPera increases available deck space on connected platforms, through the elimination of power genera tion equipment dedicated to oil and gas process ing.

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.

•• main benefits

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REDUCED EMISSIONS AND INCREASED REVENUEOPera 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 pro-vides the potential for increased oil production and improved design of connected platforms.

MORE DECK SPACE AVAILABLEOPera provides several potential benefits for the connected FPSOs. It increases available deck space through the elimination of power genera-tion equipment dedicated to oil and gas process-ing. Significant increases in revenue could there-fore 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.

IMPROVED LOGISTICSWith 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 NEEDSThe 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.

Challengesthe OPera concept

Main benefitsKey features

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•• available deck space can be used to add oil processing equipment.

•• key features

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•• 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.

•• Can be tailored to specific needs.

•• 700 MW combined cycle power plant.

•• reduced need for backup power capacity.

•• 132 kV submarine cables in closed loop configuration provides redundant connections.

Challengesthe OPera concept

Main benefitsKey features

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•• Improved operational logistics.

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oPera contactSven-erik.Borresen@dnv.comPhone: +1 832-495-9467

DNV oFFICes

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