Redeployment of North Sea FPSOs

Published Apr 6, 2004
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The challenge for the lease contractor is to find a balanced solution for the field operator that is both economically and commercially attractive, keeping in mind the FPSO’s residual value after the first and/or second project. Particularly in marginal fields, the unit must have flexibility to be easily adapted for future operations and, as such, improve its residual value.

Each of the three types of leased FPSO operations each has unique design requirements. Early production units, with 1 to 2 year operating periods, for which redeployment would require no, or only minimal, modifications. Marginal field development units, for 4 to 7 years, which are considered typical leased FPSOs with high potential for redeployment or contract extension. Large, high-capacity, long field life production units, usually company owned, with expected field life of 15 to 20 years.

Lease contractors must make strategic decisions when first designing the FPSO, to ensure future redeployment or field extension possibilities. The process of obtaining a new contract, the risks for the lease contractor and how to mitigate these risks to benefit all parties including the first client, future clients and the lease contractor must all be considered.

Commercial Challenges and Risks
Reuse or operational life extensions can be achieved by redeployment to a new location or by an extended field life in one location with additional tie-ins and upgrades. With today’s advanced subsea technology, such tie-ins become more feasible. A serious risk, lay-up between contracts may be 4 to 7 years depending on the field, while the design life of the FPSO is 15 to 20 years. Moreover, the contractor must consider the possibility of a number of years without income in the economic life of the FPSO. Another complication in remarketing an existing FPSO is the uncertainty of knowing exactly when an operating unit will be available.

Working in partnership with the client, the contractor aims for the most technically and commercially attractive solution based on the maximum reuse of what already exists and minimal modification to offer a field development possibility. Acceptance by the client of certain limitations in the existing unit can result in cost reductions for both parties.

Technical Challenges
Bluewater has been successful in field life extension/redeployment upgrades and plant extensions by designing leased FPSOs with available topside area and tie-in flexibility. While it is recognised that a first contract is tendered for in a competitive environment, leased marginal field FPSOs must be designed with the flexibility for adaptation to new operations. Bluewater has adapted a generic design approach where flexibility is afforded to consider future applications while limiting the flexibility to low-cost investments.

General Design Considerations
For a new FPSO unit, the maximum potential production capacity must be established early in the initial design. Consideration is given to unit production and storage capacity limitations, but limiting factors such as space and weight must also be considered. The design can be limited to simply leaving additional space onboard providing future expansion potential for the lowest cost implication.

Redeployment of North Sea FPSOs-Body-2

Bleo Holm FPSO

Production Plant Considerations
The production plant is the principle part of the FPSO subject to future expansion or modifications. The crude separator plant design can have free adjacent space for additional production vessels if required. Additionally, space can be provided inside the module for new coolers, heaters and pumps. A water-injection plant should leave space for an additional water-injection pump and additional booster pumps. If the required capacity for the current project is close to the determined basic or maximum operating envelope, the water treatment plan may be designed for this higher capacity including filters, dearator, etc. If produced water is used for water injection or reinjection, adjacent space should be reserved for a SO4 removal plant in case the seawater and produced water have to be mixed. Gas compression modules should incorporate space nearby for the location of a gas de-hydration unit. On the module itself, space for an additional compressor or booster compressor can also be considered.

Utilities Considerations
Utilities can usually be designed within limited cost for the selected maximum operating envelope. The initial design could include a two by 100% pumps/heaters/cooler arrangement and space for one additional piece of equipment. Double capacity can be achieved by adding one pump, cooler and an arrangement of three by 50 %. For firewater pumps, a similar arrangement can be designed by using three 100 fire pumps. Capacity can be doubled when leaving space for one additional pump, resulting in a four by 50 % arrangement.

Redeployment of North Sea FPSOs-Body

Glas Dowr FPSO

Pipe Bridges
Pipe bridges should include sufficient space for future expansions and for additional pipes, cable trays, etc. Main transfer pipes can be sized for the determined maximum capacity.

Turret Mooring System
Because a turret mooring system is difficult to modify for later phases, it should be built with the capacity to adapt to different conditions. The Bluewater multi-product swivel concept is based on a number of stacked standardised modules. This modular concept offers complete flexibility for any project requirement and can be adapted to suit the required number of flowpaths and volumes of flow. Furthermore, it allows for easy spare-part maintenance and expandability. Consequently, the space for this expandability may be incorporated in the initial design at a very low cost.

Redeployment of North Sea FPSOs-Link

Uisge Gorm FPSO

Bluewater’s FPSO Redeployment Experience
Bluewater currently operates a fleet of five high spec FPSOs and owns one new hull available for completion. We have significant experience with redeployment and operational life extensions via tie-ins, dating from 1985 to 1990, when leasing early production (EPS) FPSOs. The first Bluewater FPSOs, Aqua Blu and Lan Shui were redeployed on new field locations several times. All five of the currently owned and operated Bluewater FPSOs have been subject to upgrades for new tie-ins or redeployment.

FPSO Uisge Gorm: Originally contracted on a 4-year term to produce for Amerada Hess in 1994 on the “Fife” oil field in the UK sector of the North Sea; additional field tie-ins have since extended operations to nearly 10 years on this field.

FPSO Glas Dowr: Originally contracted for a 4-year term to produce from Amerada Hess’ Durward and Dauntlless field in the UK sector in 1996. After field production was terminated, the FPSO was then remarketed redeployed the to PetroSA’s Sable field offshore South Africa (Block 7&9).

FPSO Bleo Holm: Was contracted by Talisman Energy in 1997 to operate on the North Sea Ross & Parry Field in the UK sector. In 2000 contracted to the British Gas operated Blake field followed by the Blake-Flank tie-in.

FPSO Haewene Brim: Leased to Enterprise Oil on the Pierce field in the UK sector in 1999. 2003 contract to provide water injection facilities onboard Haewene Brim to extend the field life.

FPSO Munin: Under contract to Statoil Orient Inc. in partnership with CNOOC on the Lufeng field offshore China since 1997. In 2004, contracted to redeploy to the CNOOC Xijiang field.

FPSO Aoka Mizu: Designed with the flexibility for expansion on a generic basis for North Sea (UK & Norway) applications. The hull is based on a standard double hull Aframax design, adapted for specific FPSO requirements including improved steel qualities, improved fatigue and strength integrity, typical FPSO cargo/ballast system and a sophisticated coating system. The hull design fully complies with Norwegian regulations for FPSO.

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