Cygnus

Location and Field Details

• The Cygnus field is situated in blocks 44/11a and 44/12a of the southern North Sea, approximately 150 km off the coast of Lincolnshire, UK.
• The field is a shallow-water gas field with water depths of less than 25 meters.
• It produces gas from Leman and Carboniferous reservoirs.

Ownership and Operation

• Neptune Energy operates the Cygnus field and holds a 38.75% interest. The remaining 61.25% stake is held by Spirit Energy.

History and Development

• The Cygnus field was discovered by Marathon Oil in 1988.
• The final investment decision (FID) for the field development was made in August 2012, with an estimated cost of approximately £1.4 billion ($2.18 billion).
• The field came on stream in December 2016 with the commissioning of the Cygnus Alpha complex, and the Cygnus Bravo platform commenced production in August 2017.

Infrastructure

• The Cygnus field development includes nine horizontal wells spread across two facilities: Cygnus Alpha and Cygnus Bravo.
  • Cygnus Alpha consists of three bridge-connected platforms: a wellhead platform, a processing and utilities platform, and a living quarters and central control room platform.
  • Cygnus Bravo is an unmanned satellite wellhead platform tied back to Cygnus Alpha’s processing platform, located approximately 7 km northwest of Cygnus Alpha. Both wellhead platforms have 10 well slots each.

Production and Export

• The Cygnus field can supply up to 250 million cubic feet (mcf) of gas per day, accounting for approximately 6% of the UK’s total gas needs, which is enough to fuel around two million homes.
• Gas from the field is transported through a 55 km-long, 24-inch diameter export pipeline connected to the Esmond Transmission System (ETS) pipeline. The gas is further transported to the Perenco-operated Bacton Gas Terminal in Norfolk, UK.

Recent Developments and Contracts

• In 2022, Neptune Energy commenced a two-well infield program at Cygnus, with the 10th and 11th wells starting up in 2023. Further wells are planned to offset natural decline and increase recovery.
• Petrofac has been providing integrated support services on the Cygnus gas field since 2011, including operations, maintenance, and engineering services. A four-and-a-half-year contract extension was awarded to Petrofac in December 2016, valued at approximately £55 million ($70 million).
• Oceaneering and Stork (a subsidiary of Fluor) were awarded contracts for integrity management and fabric maintenance services in January 2021, worth approximately £4.8 million ($6.5 million).
• Neptune Energy is working with 3D technology specialist Eserv to digitize the Cygnus gas platform using 3D and artificial intelligence technologies to detect asset integrity issues early and plan fabric maintenance work.

Environmental and Operational Efficiency

• Several studies have been conducted to assess the emissions profile of Cygnus, particularly focusing on methane emissions. The field has a low methane emissions intensity of 0.028%, with a target to reduce it to 0.015%.
• The use of digital technologies, such as those provided by Eserv, allows for early detection of asset integrity issues, improved collaboration between offshore and onshore teams, and reduced need for offshore travel.

Production Life and Future Plans

• The Cygnus field is expected to have a production life of more than 20 years, with economic production potential extending beyond 2030.
• Gas compression continues to support the natural decline in reservoir pressure, and future infill wells are planned for 2024/2025 to maintain production levels.