The Cygnus gas field is a
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
reservoir and gas production facilities in the UK sector of the southern
North Sea
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...
. It is about 150 km of east of the Lincolnshire coast and started gas production in 2016.
The field
The Cygnus field extends over UK offshore Blocks 44/11a and 44/12a. The field was discovered in 1988 by Marathon Oil.
The reservoirs are
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
Leman sandstone and
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
sandstone formations and have recoverable reserves of 760 billion cubic feet.
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.
Development
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.
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.
Details of the Cygnus field infrastructure are as shown.
Production
Cygnus gas has a minimum
Wobbe Index
The Wobbe index (WI) or Wobbe number is an indicator of the interchangeability of fuel gases such as natural gas, liquefied petroleum gas (LPG), and town gas and is frequently defined in the specifications of gas supply and transport utilities.
I ...
of 46.6 to 46.8 MJ/m
3. This is below the minimum specification for entry into the
National Transmission System
The United Kingdom's National Transmission System (NTS) is the network of gas pipelines that supply gas to about forty power stations and large industrial users from natural gas terminals situated on the coast, and to gas distribution companies th ...
(47.2 MJ/m
3). 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/m
3. 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/m
3 to 46.5 MJ/m
3 at the NTS entry point at Bacton terminal was agreed in 2020.
See also
*
Bacton gas terminal
The Bacton Gas Terminal is a complex of six gas terminals within four sites located on the North Sea coast of North Norfolk in the United Kingdom. The sites are near Paston and between Bacton and Mundesley; the nearest town is North Walsham.
...
*
List of oil and gas fields of the North Sea
This list of oil and gas fields of the North Sea contains links to oil and natural gas reservoirs beneath the North Sea. In terms of the oil industry, "North Sea oil" often refers to a larger geographical set, including areas such as the Norwegi ...
*
Esmond, Forbes and Gordon gas fields
*
Tyne, Trent and Tors gas fields
References
{{coord missing, United Kingdom
Natural gas fields in the United Kingdom
North Sea energy