The Cygnus gas field is a natural gas reservoir and gas production facilities in the UK sector of the southern North Sea. It is about 150 km of east of the Lincolnshire coast and started gas production in 2016.

Cygnus gas field
CountryUnited Kingdom
RegionNorth Sea
Location/blocks44/11a, 44/12a
Offshore/onshoreOffshore
Coordinates54°34’14”N 02°17’28”E
OperatorNeptune E&P UK Ltd
OwnerSpirit Energy (61.25 %) and Neptune Energy (38.75 %)
Field history
Discovery1988
Start of productionDecember 2016
Production
Recoverable gas760×10^9 cu ft (22×10^9 m3)
Producing formationsPermian sandstones, Carboniferous

The field

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The Cygnus field extends over UK offshore Blocks 44/11a and 44/12a. The field was discovered in 1988 by Marathon Oil.[1] The reservoirs are Permian Leman sandstone and Carboniferous sandstone formations and have recoverable reserves of 760 billion cubic feet.[1]

In 2019 the Cygnus gas field was jointly owned by Spirit Energy (61.25 %) and Neptune Energy (38.75 %), Neptune E&P UK Ltd operates the infrastructure.[1]

Development

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Production from the field has been developed in stages. In the first stage gas was produced by wells on the Cygnus Alpha platform and then routed by pipeline to the Bacton Gas Terminal via the Esmond Transmission System.[1] The next stage entailed development of the north west part of the field produced from the Cygnus Bravo platform which was routed 7 km to the Cygnus Alpha installation.[1]

Details of the Cygnus field infrastructure are as shown.[1][2][3][4]

Cygnus installations
Platform name Cygnus A WHP Cygnus A PU Cygnus A QU Cygnus B
Block 44/11a 44/11a 44/11a 44/12a
Installation type Fixed Steel platform Fixed Steel platform Fixed Steel platform Fixed Steel platform
Coordinates 54°36’36”N  02°22’29”E 54°34’14”N  02°17’28”E 54°34’12”N  02°17’23”E 54°35’59”N  02°11’46”E
Function Wellheads Processing and utilities Accommodation and utilities Wellheads
Crew 66 Unattended
First gas December 2016 August 2017
Water depth, metres 22.5 22 21.7 22
Design AMEC
Jacket fabrication BiFab Methil
Jacket weight, tonnes 1,858 3,146 1,958 2,194
Topside fabrication Heerema Hartlepool BiFab Heerema Hartlepool
Topsides dimensions, metres 23 x 23 x 10
Topsides weight, tonnes 1,474 3,911 2,960 2,753
No. of legs 4 8 4
No. of well slots 10 10
No. of Wells
Production to Cygnus APU across bridge Bacton via Esmond system Cygnus A PU
Production capacity 9.1×10^6 m3 (320×10^6 cu ft) per day
Pipeline length and diameter 50 km, 610 mm 7.28 km, 324 mm (12.75 in)
Pipeline Number PL3088 PL3086

Production

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Cygnus gas has a minimum Wobbe Index of 46.6 to 46.8 MJ/m3. This is below the minimum specification for entry into the National Transmission System (47.2 MJ/m3). Cygnus gas en route to Bacton, commingles within the ETS pipeline with gas from Trent and Tors fields. The mixed gas arrives at Bacton with a minimum Wobbe index of 46.5 to 46.7 MJ/m3. If there is a reduction of gas flow from the other fields that deliver gas to Bacton then the output of Cygnus is constrained. To maintain Cygnus flow a temporary reduction of Wobbe Index from 47.2 MJ/m3 to 46.5 MJ/m3 at the NTS entry point at Bacton terminal was agreed in 2020.[5]

See also

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References

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  1. ^ a b c d e f "Cygnus gas field development". www.nsenergybusiness.com. Archived from the original on 2021-03-02. Retrieved 22 December 2021.
  2. ^ "Cygnus". www.spirit-energy.com. Archived from the original on 2018-08-14. Retrieved 22 December 2021.
  3. ^ "Inventory of Offshore Installations". odims.ospar.org. Archived from the original on 2021-11-25. Retrieved 22 December 2021.
  4. ^ "OGA interactive Maps". ogauthority.maps.arcgis.com. Archived from the original on 2019-01-26. Retrieved 22 December 2021.
  5. ^ "Amendment to Network Entry Provision at Perenco Bacton Terminal" (PDF). www.gasgovernance.co.uk. Archived (PDF) from the original on 2021-12-23. Retrieved 23 December 2020.