A-Fields natural gas fields
The A-Fields (Audrey, Ann, Alison and Annabel) are natural gas reservoirs and gas production facilities in the southern North Sea; about 123 km east of Spurn Head, Yorkshire. The fields produced natural gas from 1988 to 2016.
The A-fields
[edit]The Ann gas field was discovered as early as May 1966 and Audrey in March 1976 but there was limited local infrastructure to transport gas to shore.[1] The Lincolnshire Offshore Gas Gathering System (LOGGS) was commissioned in 1988 and designed to act as a hub and central gas processing, compression and transport facility for the area. Gas from LOGGS was routed to the Theddlethorpe gas terminal.[1]
The Audrey field is located in the UK Offshore Blocks 49/11a and 49/15a. The field was initially developed and operated by Phillips Petroleum Co. Ltd., later ConocoPhillips, then by Spirit Energy.[1] The Ann field is in Block 49/06 and 48/10a and was developed by Phillips, later ConocoPhillips, then by Spirit Energy. Alison in Block 49/11a was originally licensed to Phillips. Annabel was in Block 48/10a and was also originally licensed to Phillips, it was designed to produce gas from the Saturn gas field.[1]
The gas reservoirs in the A-Fields are Upper Leman Sandstone Formation of the Lower Permian Rotliegend Group.[2]
Phillips had assigned the letter ‘A’ to the license; all the prospects were given female names starting with ‘A’.[1]
Development
[edit]The A-Fields were developed by a number of platforms, subsea structures and pipelines.
The design parameters of the Audrey and Ann production facilities are summarised in the table.[2] [3] [4] [5] [6]
| Installation | Audrey A (WD) | Audrey B (XW) | Audrey WM | Ann A4 | Ann (XM) |
|---|---|---|---|---|---|
| Block | 49/11a | 48/15 | 49/11a | 49/06 | 49/02 |
| Coordinates | 53°32.37809'N 02°00.86304'E | 53°34.06775'N 01°58.16642'E | 53°32.42530'N 02°00.45707' E | 57.715556°N 2.056111°E | 53°42.88684'N 02°03.29081'E |
| Installation type | Fixed steel platform | Fixed steel platform | Subsea wellhead | Subsea wellhead | Subsea wellhead |
| Installed | 1987 | 1990 | 1993 | 1993 | |
| Water depth, metres | 27 | 30 | 27 | 29 | 29 |
| Substructure weight, tonnes | 1,063 | 865 | 34.62 | 2 x 13.2 | |
| Topsides weight, tonnes | 1,276 | 1,298 | – | – | – |
| No. of legs | 4 | 4 | – | – | – |
| No. of Wells | 10 | 4 | 1 | 1 | 2 |
| Gas export to | LOGGS PP | Audrey A | Audrey A | Ann XM | LOGGS |
| Export pipeline length, diameter | 16.9 km, 20-inch | 4.4 km, 14-inch | 0.492 km, 8-inch | 0.128 km, 6-inch | 41.8 km, 12-inch |
| Pipeline number | PL496 | PL723 | PL575 | PL2164 | PL947 |
The design parameters of the Alison, Annabel and Ensign production facilities are summarised in the table. [2] [6] [5]
| Installation | Alison (KX) | Annabel AB1 | Annabel AB2 | Annabel template | Ensign |
|---|---|---|---|---|---|
| Block | 49/11a | 48/10a | 48/10a | 48/10a | 48/14a |
| Coordinates | 53.509234°N 2.169722°E | 53.675000°N 1.925000°E | 53.682500°N 1.925000°E | 53.681633°N 01.923609°E | 53°35.4322'N 1°46.3988'E |
| Installation type | Subsea wellhead | Subsea wellhead | Subsea wellhead | Subsea manifold | Fixed steel platform |
| Installed | 1995 | 2005 | 2005 | 2005 | 2011 |
| Water depth, metres | 23 | 30 | 30 | 30 | 23 |
| Substructure weight, tonnes | 582 | ||||
| Topsides weight, tonnes | – | – | – | – | 530 |
| No. of legs | – | – | – | – | 4 |
| No. of Wells | 1 | 1 | 1 | – | 3 |
| Gas export to | Alison Tee on the Ann to LOGGS pipeline | Annabel template | Annabel template | Audrey A | Audrey A |
| Export pipeline length, diameter | 0.048 km, 8-inch | 0.037 km, 8-inch | 0.133 km, 8-inch | 17.8 km, 10-inch | 17 km, 10-inch |
| Pipeline number | PL947 | PL2066JW12 | PL2066JWAB2 | PL2066 | PL2838 |
In addition to the gas production pipelines there were also 3-inch methanol pipelines from LOGGS to Audrey A and B and to Ensign. There were also control umbilicals to the subsea wellheads.[3]
Gas production
[edit]A summary of the key gas production data for the A-Fields is shown in the table.[7]
| Field | Audrey | Ann | Alison | Annabel | Ensign |
|---|---|---|---|---|---|
| Start of production | 1988 | 1993 | 1995 | 2005 | 2012 |
| Peak flow, million cubic metres/y | 2,413 | 488 | 81 | 901 | 150 |
| Year of peak flow | 1990 | 1994 | 1996 | 2006 | 2013 |
| Cumulative production to end of 2014, million cubic metres | 19,796 | 2,869 | 697 | 3,413 | 255 |
| Production ceased | May 2016 | 2012 | 2010 | May 2016 | 2018 |
The gas production profile, in mcm/y, for Audrey is as shown.[7]
 | Graphs are unavailable due to technical issues. There is more info on Phabricator and on MediaWiki.org. |
Decommissioning
[edit]The Alison and Ann fields had reached the end of their economic lives in 2010 and 2012 and were closed-in. Audrey was shut down in 2016. Ensign was still operating but the closure of LOGGS and Theddlethorpe gas terminal in August 2018 closed the gas export route; when no alternative export route was found the Ensign installation was decommissioned.[8]
See also
[edit]- List of oil and gas fields of the North Sea
- Theddlethorpe Gas Terminal
- Lincolnshire Offshore Gas Gathering System
- Easington Catchment Area
- Planets gas fields
References
[edit]- ^ a b c d e Department of Trade and Industry (1994). The Energy Report. London: HMSO. pp. 27, 28, 121, 134. ISBN 0115153802.
- ^ a b c Asset Data Sheets for Audrey, Ann, Alison, Saturn (Annabel) Centrica
- ^ a b "Audrey Decommissioning Programmes" (PDF). assets.publishing.service.gov.uk. Archived (PDF) from the original on 2019-07-24. Retrieved 12 December 2021.
- ^ "Ann and Alison Fields Decommissioning Programmes" (PDF). assets.publishing.service.gov.uk. Archived (PDF) from the original on 2021-12-13. Retrieved 12 December 2021.
- ^ a b "Inventory of Offshore Installations". odims.ospar.org. Archived from the original on 2021-11-25. Retrieved 12 December 2021.
- ^ a b "OGA interactive Maps". ogauthority.maps.arcgis.com. Archived from the original on 2019-01-26. Retrieved 12 December 2021.
- ^ a b "Oil and Gas UK – Field data". www.gov.uk. Archived from the original on 2015-10-27. Retrieved 12 December 2021.
- ^ "Ensign Installation Decommissioning Programme" (PDF). spirit-energy.com. Archived (PDF) from the original on 2021-12-13. Retrieved 12 December 2021.