Valhall

Location and Geology

The Valhall oil field is situated in the southern part of the Norwegian sector of the North Sea, approximately 30 kilometers south of the Ekofisk Platform complex. The water depth at the field is around 70 meters.

The oil and gas reserves at Valhall are located within the chalk rocks of the Tor and Hod formations of the late Cretaceous age, at a reservoir depth of approximately 2,400 meters. The Tor Formation chalk is fine-grained and soft, with considerable fracturing that allows oil and water to flow more easily than in the underlying Hod Formation.

Discovery and Development

The Valhall oil field was discovered in May 1975 by Amoco Norway through the 2/8-6 discovery well. The field was appraised by drilling the 2/8-7 and 2/8-8 wells in 1976 and declared commercial the same year. The development plan approval for the field was granted in 1977.

Initial production began in October 1982, with the field originally developed using three facilities: the Quarters Platform (QP), the Drilling Platform (DP), and the Production and Compression Platform (PCP).

Infrastructure and Platforms

The Valhall complex currently comprises six separate manned platforms:

• Quarters Platform (QP)
• Drilling Platform (DP)
• Production and Compression Platform (PCP): Decommissioned in October 2013 and replaced by the new Process and Hotel Platform (PH).
• Wellhead Platform (WHP): Installed in April 1996 with 19 well slots.
• Water Injection Platform (IP): Installed in 2003 to improve oil recovery, with an injection capacity of 180,000 barrels of water per day.
• Process and Hotel Platform (PH): Commissioned in January 2013, this platform has an oil production capacity of 120,000 barrels per day, a gas handling capacity of 143 million standard cubic feet per day, and a total liquid capacity of 200,000 barrels per day (oil and produced water). It is powered from shore via a 292km-long cable from Lista.

In addition to the manned platforms, there are two unmanned flank platforms:

• Valhall South Flank platform: Installed in 2002 with 16 well slots.
• Valhall North Flank platform: Installed in 2002 with 16 well slots. Both platforms are located approximately 6 kilometers from the main Valhall facilities and are powered from the main complex via a fibre-optic cable.

Production and Reserves

The Valhall field has produced over one billion barrels of oil equivalents since its opening in 1982. As of 2014, the remaining recoverable reserves were estimated at 251.8 million barrels of oil, 7.1 billion cubic meters of gas, and one million tonnes of natural gas liquids (NGL).

The field's production has been significantly extended through various redevelopment projects. The Valhall Redevelopment project, approved in June 2007 and completed in January 2013, extended the field life to 2050.

Recovery Strategy

The field was initially produced using pressure depletion and compaction drive. Water injection in the center of the field started in 2004 to improve the oil recovery factor from 31% to 38%, yielding an additional 29 million cubic meters of oil. Gas lift is also used to optimize production in most of the production wells.

Transport

Oil and natural gas liquids (NGL) are exported via a 20-inch diameter pipeline to the Ekofisk field and then to Teesside in the UK. Produced gas is exported via the Norpipe pipeline to Emden in Germany.

Recent Developments and Future Plans

• Valhall Flank West: A new normally unmanned wellhead platform was put into production at the end of 2019, setting a new standard for flank developments.
• New Central Platform: Aker BP is currently working on a new central platform that will enable an additional 40 years of production. This involves removing old platforms, plugging old wells, and investing in new wells.
• Decommissioning: The first phase of decommissioning the old facilities started in 2015 and is expected to continue until 2026. Decommissioning of the QP, PCP, and DP facilities must be completed by the end of 2026. A new production and wellhead platform (PWP) is expected to start production in 2027.

Operators and Partners

The Valhall field is operated by BP, which holds a 35.95% interest. The remaining 64.05% interest is held by Hess Norge.

Environmental and Operational Innovations

• Power from Shore: Since 2013, the Valhall field has been operated with electricity from shore, reducing the field's carbon footprint.
• 4D Seismic System: The field is equipped with a permanent life-of-field seismic system, featuring a 4D streamer with approximately 10,000 sensors in the seabed, enabling accurate 4D surveys.

The Valhall field's extensive redevelopment and innovative operational strategies have significantly extended its production life and enhanced its recovery efficiency.