West Africa has seen floating production systems before, but Exxon's Yoho project is the first early production system (EPS) deployed in that part of the world.

Deploying an EPS on Yoho allows ExxonMobil to get to first oil 2 years earlier than a full floating production facility would allow. Effectively, it has taken a shortcut on the route to a fast-track floating production, storage and offloading (FPSO) vessel.

"Once Yoho's permanent production facilities are in place, we'll move the EPS to another project, and then potentially to another one after that," said Robert Talbot, technical manager for Nigeria Projects, ExxonMobil Development.

Morris Foster, president of ExxonMobil Development, said, "We're now able to produce oil much earlier than we could with permanent facilities. That's not only a big plus for us, but also for our project partners," he said, talking to Exxon's in-house magazine, The Lamp.

With an average FPSO build time (from concept to first oil) of around 5 years, the EPS makes a lot of sense when the oil price is high. On Yoho, ExxonMobil, through Mobil Production Nigeria (MPN), will be using the FPSO Falcon for the EPS in partnership with the National Nigeria Petroleum Company (NNPC).
"The primary reason for use of the generic FPSO at Yoho is the acceleration of production from the field by 2 years, a significant benefit to Nigeria and ourselves," said Marcia Zelinsky, a US-based spokeswoman for ExxonMobil's upstream operations. "Since the FPSO Falcon was available and is considered to be economically attractive, NNPC and MPN ...elected to install it as an early production system at Yoho."

Zelinsky pointed out that FPSOs are particularly well-suited for deepwater field locations such as discoveries offshore Nigeria, Angola and Equatorial Guinea, "where the cost of bottom-supported structures to support the production facilities is either more expensive or technically impractical.

"For small fields with relatively short production lives or for early production operations, the flexibility and portability of FPSOs can provide an opportunity to share the costs of construction of the facilities across multiple fields and thereby, allow economic production that would otherwise not be practical," Zelinsky said.

"The early production system offers a significant shortening of time between discovery and oil production by as much as 2 years," said Foster. "This strategy provides us greater flexibility for future offshore developments and reduces costs by standardizing one design and utilizing near identical equipment from one vessel to another. By utilizing these general purpose FPSOs to commercialize our significant portfolio of offshore developments, we are able to deploy a safe and environmentally sound production system long before custom-design facilities can be ready, allowing the resource to come onstream in a shorter time frame."

At the center of the Yoho EPS is a floating production, storage and offloading vessel classed by the American Bureau of Shipping. The ship, the 315,000-dwt, very large crude carrier Falcon, is leased from Single Buoy Moorings for a total of 6 years with 18 months assigned for the Yoho EPS. It is one of three units to be delivered through Single Buoy Moorings from yards in Singapore and Dubai and classified by the American Bureau of Shipping for West Africa. Classification and certification work by ABS on the three floating units includes condition assessment and a review of the technical designs, plus surveying during refurbishment, conversion, hook-up and commissioning.

The Falcon features an external turret mooring and a swivel stack containing production risers and umbilicals. It has storage for up to 2.2 million bbl of oil, and oil processing capacity of 90,000 b/d. It also has gas injection capacity of 95 MMcf/d and gas lift and export capacity of 20 MMcf/d.

Yoho is a shallow development in depths between 200 ft to 300 ft (61 m to 92 m) of water. The EPS comprises an initial wellhead platform, designated YA, built by Global Offshore International, under an engineering procurement and construction (EPC) contract. Nigerian company Weco was contracted for fabrication of the YA jacket.

Sixteen wells are hooked up to the FPSO to produce 90,000 b/d of oil. Full development of Yoho will see three further wellhead platforms, designated YB and YQ - with living quarters - plus one on the nearby Awawa field discovered by the NNPC in 1978.

A central production platform, YP, a flare stack, YZ, plus a floating storage and offloading (FSO) vessel with storage for 2 million bbl will complete the project. These facilities, due onstream in the fourth quarter of 2004, are expected to become a development hub for other prospects in Nigeria's Offshore Mining Lease 104. This enlarged layout is expect to see 34 development wells and produce up to 150,000 b/d of oil, while gas will be re-injected to avoid routine flaring and provide reservoir pressure support. It will also allow the option for commercializing gas later.

SaiBos, the Saipem/Bouygues Offshore joint venture, has been awarded a second EPC contract on Yoho for the main production facilities using Nissco's yard in Warri, Nigeria.

Estimated recoverable reserves within the overall $1.2 billion development are put at 400 million bbl of oil; 75 million of those bbl will be produced through the Yoho EPS.

Putting together the early production plan was done with repeatability in mind. "The concept is based on a generic design of floating storage and offloading vessel, " said Ken Larson, EPS project manager for ExxonMobil Development. "This makes it suitable for use in a wide range of environments such as different water depths and in fields with different reservoir characteristics.

"Generic design allows for faster development of offshore discoveries around the world. And it results in lower developed costs, which enables smaller fields to be developed that otherwise might not be produced."

Data obtained during the life of the EPS will inform later planning. "The use of an early production system in developing a large field gives us data that are extremely helpful to our reservoir engineers in planning full field development," says Larson. "Although an EPS is not appropriate for developing every discovery, it is an ideal model in many cases."

Yoho, discovered in 1991 about 55 miles (88 km) miles south of an oil terminal at Qua Iboe in Nigeria's OML104, came onstream in February, two years ahead of the planned full field start after completion of the ship by Keppel FELS in Singapore.

ExxonMobil's second generic floater from SBM is the FPSO Amazon Eagle, re-christened the Serpentina after another conversion at Keppel's Far East Levington Shipyard in Singapore. It is destined for an expansion project on the southern area on the Zafiro field in block B offshore Equatorial Guinea in September. It also features an external mooring turret and swivel stack with provision for 10 flow paths, including spares. This unit will be located in a water depth of 1,600 ft (490 m) with a total of 21 wells, 14 for production and five for water injection. This unit is designed for a throughput of 110,000 b/d, and to import 185,000 b/d of oil.

The third generic unit is the FPSO Atlantic, destined initially for a $350 million EPS on Exxon's Xikomba development in block 15 off Angola. Based on a conversion of the former Atlantic VLCC, this FPSO is to be installed in a water depth of 4,264 ft (1,300 m), where it is expected to pump up to 90,000 b/d of oil with four oil production wells, plus five injector wells (four for water and one for gas). It also features an external mooring turret and swivel stack with 10 flow paths.

Some market data provided by Single Buoy Moorings on the use of FPSOs shows that it has taken the offshore industry about 15 years to accept FPSOs as an operational tool for short or long duration field developments in either shallow or deep water, stationed on marginal to giant fields.
Jacques Burger, senior vice president of lease business development at Single Buoy Moorings, told those attending a London floating production conference in 2002 that there are now 60 FSOs and 75 FPSOs operating worldwide. Fifty percent of the FPSOs have been installed in the past 5 years, indicating increased popularity of floating production technology. He predicted FPSO usage will double again in the next 5 years, so we could see 150 of them by 2007. By then, generic designs may well have matured even more.

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