Long talked about as the future for the North Sea industry, the west of Shetlands region is facing a crunch year. Two major new projects, Clair and Magnus, are paving the way for the start of a new chapter about exploiting finds that until now have been beyond the reach of conventional technology.

Bidding should begin soon for the Clair field, a 4 billion-bbl prize using the first fixed steel platform installed west of the Shetland Islands. Production is scheduled for 2005. In addition, a gas export trunk line is being laid as part of the Magnus enhanced oil recovery (EOR) project, which will allow associated gas from Foinaven, Loyal and Schiehallion - and future fields - to be exported to an onshore terminal.
These are the cornerstones of the new west of Shetland infrastructure. Clair is coming, and Magnus may be followed by more.
Most of the contractors in Europe who care know what field facilities BP wants for Clair, which is still to be exploited. Mustang Engineering and Noble Drilling completed two front-end engineering and design (FEED) studies - one for a platform design concept and a second for drilling facilities - earlier this year.
It remains for the field partners - BP, Enterprise Oil, Chevron, Amerada Hess and Conoco - to make a decision on sanctioning the project.
"We hope to have a sanctionable project before the end of the year based on a 250 million-bbl development and total investment of US $750 million," Steve Marshall, BP's regional president in the United Kingdom, said.
In September 2000, Sir John Browne, group chief executive, said Clair would be a $750 million (£500 million) project with a life-of-field investment of $1.5 billion (£1 billion).
Browne spoke then of sanctioning the project by this summer and construction work starting by early 2002. A target onstream date of 2004 and a daily rate of 60,000 b/d of oil also were projected.
Facilities
Based on what is known about the reservoir, BP and its partners are planning a single steel platform-based development concept (Figure 1).
The design is likely to be based on a steel platform already operating offshore West Africa. The costs for each of the platform elements were put at:
• jacket, $25 million (£18 million);
• deck, $109 million (£78 million);
• drilling facilities, $41 million (£29 million); and
• other facilities, $63 million (£45 million).
Processing capacity on the platform is expected to be about 60,000 b/d of oil. A heavy requirement for water handling also is anticipated with a total liquids throughput in the range of 120,000 b/d.
BP said there are "no other known fields analogous to this reservoir," which indicates just how hard it will be for BP to come up with a development plan for the highly fractured chalk reservoir compartments that comprise the Clair discovery.
Between 25 and 30 wells have been suggested for the field. Emphasis also has been placed on skidded modules, which suggests flexibility is needed to change platform process units once it is installed in the field. A single lift is a further requirement of the preferred design, which will comprise two process decks and a weather deck.
This new platform initially will target the Core, Graben and Horst segments at the southern end of the Clair reservoir, with the object of tapping mean recoverable reserves of 242 million bbl over a field life of 20 years. (The 4 billion-bbl reserves figure is the estimate of total oil initially in place). Even these recovery numbers are pessimistic, given the size of the total reserve base. But a 14% recovery factor is expected, based on existing reservoir knowledge, which already has indicated the field is highly compartmentalized and fractured.
The reservoir spans 85 sq miles (220 sq km), and the field spans five license blocks in nine segments, about 47 miles (75 km) west of the Shetland Islands.
Before the FEED work was completed, BP talked about a steel platform to exploit Clair and its peak oil production rate of 60,000 b/d based on recoverable reserves of 250 million bbl.
Drilling
Drilling on Clair has been extensive. The field was discovered in July 1977 with the 206/8-1a well on 4th Licensing Round acreage that hit a Carboniferous and Devonian formation in license P.165.
Between 1977 and during the 1980s, another 10 appraisal wells were drilled on Clair.
Knowledge of the field took a big step forward in 1996 with the 206/8-10z well in the Core area, which produced 525 bbl of oil during a test.
Two less successful wells targeting the field's Graben and so-called "3A" areas were drilled in 1997, but both were regarded as disappointments.
So planning is based on the field's southern portion, and the platform concept reflects the need to provide the maximum versatility in the drilling and production facility.
It must have a single integrated deck, with both the supporting jacket and topsides capable of installation in single lifts.
Further specifications revealed a desire for all platform development wells to have dry wellheads - perhaps reflecting a requirement for frequent workovers.
Full offshore processing and power generation is required to allow export-quality crude to be produced.
Other facilities will include water injection, produced water reinjection, flare gas recovery and surplus gas disposal, either via reinjection or through the Magnus EOR pipeline being laid this summer.
Furthermore, artificial gas lift is anticipated for all production wells, and these are expected to be high-angle horizontals. Subsequent development and workover wells also are expected to require either gas lift or electric submersible pumps.
BP will acquire 23 wells - 14 producers and eight water-injector wells, plus a possible one or two more for reinjection of drill cuttings.
Making Magnus magnificent
EOR is not a new idea, but when BP decided to apply it to Magnus, the northernmost producing field in the UK North Sea, it was thinking about getting out an extra 50 million bbl of oil - more than the size of the average discovery on the UK Continental Shelf.
The project also will extend the field's life to 2015, possibly 2018, while creating environmental and commercial spin-offs for BP's assets west of the Shetland Islands. Magnus EOR provides pipeline infrastructure that can be used for any future gas finds in the deepwater region west of the Shetlands, including Clair.
Magnus EOR is a $420 million (£300 million) project that involves taking gas from Foinaven, Loyal and Schiehallion, where it is dumped into reinjection wells or flared. Instead, gas will be exported via a new 20-in., 116-mile (186-km) pipe to the Sullom Voe oil terminal, where it will displace liquid fuels used for power generation. This section of the line will have a midpoint T-piece installed, protected in a steel cage, "to enable future tie-in of other gas sources in that area," an environmental statement on the project pointed out, indicating BP expects this line to tap other west of Shetland gas deposits.
At Sullom Voe, the gas will be enriched with natural gas liquids and transported via a 20-in., 131-mile (210-km) line to Magnus. There, the enriched gas will be injected through six existing seawater injection wells into the edges of the Magnus reservoir, to provide a better sweep. Eventually the injected gas will be removed and exported via the Northern Leg Gas Pipeline and Far North Liquids and Gas System pipeline to St. Fergus in northeast Scotland.
Injecting enriched gas into the Magnus reservoir combined with new drilling technology will offer benefits on several fronts. First, more oil recovered from Magnus means more money, and it is expected the project will extend the life of the field by up to 5 years to 2018. Gas from the Foinaven and Schiehallion fields will earn revenue rather than be reinjected in gas disposal wells.
First gas is due to start reaching Magnus early in 2002.
Foinaven, Schiehallion and Loyal fields are in quadrant 204, 110 miles (177 km) west of Shetland. All three fields are in water deeper than 1,440 ft (440 m) and came on stream in 1997 and 1998. Combined production is some 200,000 b/d. Associated gas is reinjected.
It is clear BP has a strong hold on the operating assets in the west of Shetlands region. But the picture may change. This summer, Conoco spudded the second of two west of Shetland exploration wells. Both were drilled with Smedvig's West Navion drillship. The first of those Conoco wells, 136/6-1, was completed with tight status in June, and the second, 204/15-2, north of Foinaven and Schiehallion, was spudded days later. It also is just north of the June 1996 Suilven oil discovery made by Britoil (BP) with the 204/19-8z well. Subsequent to the Suilven discovery, BP asked the UK Department of Trade and Industry for an out-of-round license award for the acreage in the vicinity of Suilven. Conoco became operator of that acreage in the out-of-round license award.
If Suilven is undergoing appraisal drilling by Conoco, Foinaven and Schiehallion clearly offer potential development options. With a gas export pipeline in place as well, Suilven looks even more certain. And then there is the Onslow prospect, drilled with the second of two exploration wells by Arco (prior to its takeover by BP) in 1998. The first of these wells, 204/14-1, was an appraisal of the northerly extent of Suilven. The second, 204/14-2, appraised Onslow.
Meanwhile, Amerada Hess, a license holder in some of the surrounding acreage, is seeking contractors to provide development solutions for its Solan and Strathmore oil fields, which lie 18 miles (25 km) south in blocks 205/26a and 204/30a, respectively. These two fields, thought to contain 340 million bbl of oil, might become other customers for burgeoning west of Shetland infrastructure.
And then there is the exploration drilling on the United Kingdom's 19th Licensing Round acreage, plus what is licensed by the Faeroes Islands and due to be drilled this summer, along the white zone median line between the United Kingdom and the Faeroes. BP, Statoil and Amerada Hess are to drill the first three Faeroes wells, which will use the West Navion and Sovereign Explorer drilling platforms.
In the 19th Round in February, BP was awarded Block 204/18, northwest of Foinaven and southwest of Suilven, thus extending its grip on what is becoming a key area of operation.

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