The Statfjord area lies on the border between the Norwegian and British sectors in the northern part of the North Sea. The Statfjord area consists of one field, three satellite fields, and three Condeep concrete production platforms: Statfjord A, B and C. The three satellite fields that make up the Statfjord area are Sygna, Statfjord North and Statfjord East; all three process and export hydrocarbons to the three concrete platforms.

Statoil is operator of the entire Statfjord area, but interests and partners vary within each field.

Statfjord

The Norwegian share of the Statfjord field lies on Blocks 33/9 and 33/12 in production license 037, while the British section is located on UK Block 211/25 in licenses 104 and 293. The Statfjord field is located in the Tampen area in water depths of 492 feet (150 meters). StatoilHydro owns 44.34% interest of the Statfjord area; ExxonMobil Norway owns 21.37%; Norske ConocoPhillips owns 10.33%; Norske Shell owns 8.55%; ConocoPhillips UK AS owns 4.84%; Centrica Resources AS owns 9.68%; and Enterprise Oil Norge AS owns the remaining .89%.

The hydrocarbon reservoir formations are in Jurassic sandstones belonging to the Brent group, and the Cook and Statfjord formations. The reservoir consists of sandstones, with the oil and gas held in pores between the individual sand grains. The reservoir is located at a total depth of 8,202 to 9,843 feet (2,500 to 3,000 meters).

Mobil discovered the Statfjord field in 1974; the field came online in 1979; and Statoil gained ownership of the field on Jan. 1, 1987.

In 2004, the field celebrated its 25th anniversary. Since its inception, it has yielded 4 Bbo and 2.5 Bcf (70 Bcm) of natural gas. Statfjord is considered to be one of the oldest producing fields on the Norwegian Continental Shelf and the largest oil discovery in the North Sea.

The field reached peak production of 850,204 in 1987. Currently, it produces about 140,000 barrels of oil per day.

Field Development

Field development in the area relies on pressure support from water alternating gas injection (WAG) in the Brent reservoir; pressure support from water injection and supplemental gas injection from the Statfjord formation; and phasing in wells penetrating the reservoir or by deepening wells in the Cook formation.

Hydrocarbons from the reservoirs are sent to three gravity-base concrete and steel topside production platforms that produce Statfjord and its satellite fields. The three concrete platforms have drilling modules, living quarters, oil derricks, cranes, towers, storage bins and a base. The platforms are similar in design, except Platform A is slightly smaller in size than Platforms B and C.

Roughly 150,000 to 160,000 bopd are produced by the three Statfjord platforms, which unite all the licenses.

Platform A

Centrally positioned on the Statfjord field, Platform A consists of 19 cylindrical storage tanks (cells) that hold 7.3 MMscf (206,000 cubic meters) and 1.3 MMbo. Three of the cells at the base rise and form tower shafts supporting a steel deck. The total weight of the platform is 661,387 tons (600,000 tonnes), and the height is of 886 feet (270 meters).

Platform A came online Nov. 24, 1979.

Platform B

Platform B is located 112 miles (180 kilometers) west of the Norwegian coast and is positioned on the southern part of the Statfjord field.

Platform B features 24 storage cells that are 210 feet high (64 meters high) and 75 feet wide (23 meters wide), with a combined storage capacity of 2 million barrels of oil and 10.7 MMscf (302,000 cubic meters). Four of the cells rise and form the concrete legs that support the deck. The deck weighs 44,092 tons (40,000 tonnes) and has topsides for processing and accommodation facilities. The total height of the platform is 889 feet (271 meters) from the seafloor to the top of the drilling deck, and the total weight of the platform is 899,486 tons (816,000 tonnes).

The platform commenced production Nov. 5, 1982.

Platform C

Platform C is located on the northern part of the field. Platform C is a replica in design to Platform B. The platform weighs 709,558 tons (643,700 tonnes) with a total height of 951 feet (290 meters).

The concrete platform came online on July 2, 1985.

Satellite Fields

Sygna

The Sygna oil field is located in the northeast corner of the Statfjord area. The field lies in between two production licenses: 55% of it is located on Block 33/9, and 45% is located on Block 34/7.

Petoro owns 30% interest in the field; StatoilHydro owns 30.71%; ExxonMobil Norway owns 18.48%; Norske ConocoPhillips owns 6.65%; Norske Shell owns 5.50%; Idemitsu Petroleum Norge owns 4.32%; Total E&P Norge owns 2.52%; RWE Dea Norge owns 1.26%; and Enterprise Oil Norge owns the remaining .57%.

The field was developed through a subsea template tied-back to Statfjord C Platform by a pipeline. Two production wells were drilled through the template, and water is injected into the reservoir through an extended-reach well drilled from the Statfjord North satellite field.

Sygna commenced production August 1, 2000, and it has a life expectancy of 19 years.

Statfjord North/Statfjord East

Statfjord North and Statfjord East are two satellite fields that were developed together. In 1977, Statfjord North was discovered on Block 33/9; Statfjord East was discovered in the same year, and it lies on production licenses 037 and 089.

Both fields have the same ownership. Petoro owns 30% interest; Norske Shell owns 10%; ConocoPhillips owns 12.08%; StatoilHydro owns 21.87%; ExxonMobil Norway owns 25%; and Enterprise Oil Norge owns the remaining 1.05%.

The fields have a total of six four-slot subsea templates. Combined, the satellite fields have two production templates with each one having three production wells, and one water-injection template with four injection wells. The templates are tied-back to the Statfjord C platform. FMC Technologies completed the subsea development of the two fields.

Late Life Field Development

Since Statfjord has been online for two decades, the oil reserves are declining. In order for the Statfjord area to continue to produce, the three platforms will be modified to handle gas with associated oil, rather than handling oil with associated gas. Additionally, a pipeline will be built to transport the newly produced gas. The project is expected to cost US $2 billion (NOK 17.9 billion).

This project is referred to as 'late life' and involves terminating gas injection on the field and reducing pressure in the reservoir. The modified plan to Statfjord and the plan for constructing and installing the Tampen Link were approved by the Norwegian government June 8, 2005. Conversion work on the platforms began in the fall of 2005. Platform B will be modified to handle low-pressure production in 2009; Platform C will be modified in 2010; and Platform A will be shut down in 2013.

By doing this, the Statfjord area's life span is expected to increase until 2020. Statfjord's late life recoverable reserves are estimated at 1,130 Mcf (32 Bcm) of gas, 25 MMbo and 60 million barrels of condensate.

Produced gas is sent through a newly constructed pipeline named the Tampen Link. The 14.35-mile-long (23.1-kilometer-long), 32-inch-diameter pipeline connects the Statfjord B platform to the Flags pipeline on the Norwegian Continental Shelf. The pipeline was laid by the Saipem-owned Castoro Sei pipelay vessel in 2006, and gas production began transferring from the Norwegian portion of the Statfjord field on Oct. 12, 2007. StatoilHydro transferred operatorship of the pipeline to Gassco when production commenced.