Forties

Location and Discovery

The Forties Oil Field is situated approximately 110 miles (177 km) offshore from Aberdeen, within the UK production block 21/10 in the North Sea. It was discovered by British Petroleum (BP) in October 1970.

Geology and Reservoir

The Forties Field is trapped in a simple four-way dip closure and features a Paleocene turbidite sandstone reservoir, specifically the Forties Formation, which includes a lower Shale Member and an upper Sandstone Member deposited in a submarine fan environment.

Development and Production History

• Initial Development: The field was brought into production in September 1975, with the official inauguration by the Queen on November 3, 1975. The initial development included the installation of four fixed steel platforms: Forties Alpha, Forties Bravo, Forties Charlie, and Forties Delta. A fifth platform, Forties Echo, was added in the 1980s.
• Peak Production: Production peaked at 500,000 barrels per day (bpd) in 1979, contributing significantly to the UK's oil demand at the time.
• Water Injection: The field's production has been supported by a complete replacement seawater injection system starting in 1975, and later by the influx of a regional aquifer.

Platforms and Infrastructure

• Platforms: The field comprises five fixed steel platforms:
  • Forties Alpha: Serves as the central hub and gathering platform for all production. It hosts separation and processing facilities and is connected to the Forties Unity Riser Platform via a 36-inch export pipeline.
  • Forties Bravo: Converted into a direct export facility for non-stabilised produced fluid.
  • Forties Charlie: Hosts separation and processing facilities and acts as the main hub.
  • Forties Delta: Hosts separation and processing facilities.
  • Forties Echo: Does not include any separation facilities; well fluids are transferred to Forties Alpha for processing.
• Forties Alpha Satellite Platform (FASP): Constructed and commissioned in 2013, the FASP is located adjacent to the main Forties Alpha platform and provides 18 new drilling slots, additional liquids processing, and gas compression capacity. It was built by OGN Group and connected to the existing Forties Alpha platform by a 90m bridge.

Ownership and Operations

• BP (1970-2003): BP operated the field from its discovery until 2003, when it sold a 97.14% working interest to Apache Corporation for approximately $630 million. Esso Exploration and Production UK and Shell UK hold the remaining interests of 2.61% and 0.25%, respectively.
• Apache Corporation (2003-Present): Apache acquired the field and immediately initiated a re-evaluation and intensive drilling campaign, which extended the field's life by at least 20 years. Apache has continued to invest in the field, including the construction of the FASP, and has produced significant additional reserves using advanced seismic technologies.

Production Statistics

• Historical Production: The field produced over 2.4 billion barrels of oil by the time Apache took over in 2003. Peak production was 500,000 bpd in 1979. By 2013, the field was producing 41,704 barrels of oil and 10 million cubic feet of associated gas per day, making it the second-highest producing field in the UK after the Buzzard field.
• Recent Production: Production declined to around 20,000 bpd in 2021. However, the field's life has been extended through continuous investment and new drilling campaigns.

Reserves and Future Prospects

• Initial Reserves: The field originally contained between 4.2 and 5 billion barrels of oil. By June 2017, 2.75 billion barrels had been produced.
• Current Reserves: As of 2011, the proven oil reserves were estimated at 174 million barrels. Apache's efforts have added over 170 million barrels of oil reserves, extending the field's life beyond 2030.

Contractors and Contracts

• OGN Group: Awarded a £400 million contract to design and build the FASP in 2010.
• KANFA Aragon: Awarded a contract to deliver the Triethylene Glycol (TEG)-based dehydration module for the FASP in 2011.

Environmental and Decommissioning Considerations

• Decommissioning: Initially anticipated to start decommissioning in 2013, the field's life has been extended by at least 20 years due to Apache's investment and new discoveries.

The Forties Oil Field remains a significant asset in the UK North Sea, with ongoing efforts to maximize its production and extend its operational life.