Hewett gas field

The Hewett gas field is a large natural gas and associated condensate field located under the North Sea 19 miles (30 km) off the Norfolk coast.

Hewett gas field
CountryUnited Kingdom
RegionSouthern North Sea
Location/blocks48/28, 48/29, 48/30, 52/4, 52/5
Offshore/onshoreOffshore
Coordinates53°01′03″N 1°47′43″E
OperatorPhillips Petroleum (1966-2000), Tullow Oil (2000-2008), Eni UK (2008- )
Field history
Discovery1966
Start of development1967
Start of production1969
Peak of production1976
Production
Current production of gas819×10^6 cu ft/d (23.2×10^6 m3/d)
Recoverable gas3,500×10^9 cu ft (99×10^9 m3)
Producing formationsBunter sandstones

The field

The Hewett gas field is a natural gas field located in the UK North Sea. The field is named after the Hewett Ledges a sand bank feature beneath which the field is situated.[1] The gas reservoir is a Lower Triassic (Middle and Lower Bunter) sandstone and a Permian Zechstein carbonate bed at a relatively shallow depth of 3,000–4,200 feet (914–1,280 m). The Hewett structure runs north-west to south-east and is about 18 miles long and 3 miles wide (29 km by 4.8 km).[2] It was discovered in October 1966 and extends over blocks: 48/28, 48/29, 48/30, 52/4 and 52/5. To the north are the Big Dottie, Little Dottie and Deborah accumulations, which are separate from Hewett, but are produced through the Hewett topsides facilities. The original determination of the gas in place amounted to 115 billion cubic metres.[1] The field was originally licensed to Phillips Petroleum Exploration UK Ltd (then from 2001 Tullow Oil UK Ltd and from 2008 Eni UK Ltd). Production from the field began in July 1969. Gas and associated condensate are exported from the field via two 30 inch diameter pipelines to the Bacton gas terminal, Norfolk. Eni submitted plans in 2019 to decommission the Hewett field and to remove all installations.[3] The end of production is scheduled for late 2021.[3]

The Hewett gas compositions and properties are as follows.[4]

Hewett gas properties
Composition Middle Bunter % Lower Bunter %
Methane 86.57 92.13
Ethane 4.87 3.56
Propane 1.40 0.85
Butane and Pentane 0.32 0.56
Nitrogen 6.57 2.36
Carbon dioxide 0.09 0.02
Hydrogen sulfide 500 ppm Nil
Gas gravity 0.655% 0.607%
Mean condensate content 3.2 bbl/million cu ft 4.8 bbl/million cu ft
Btu rating 1011 Btu/cu ft 1047 Btu/cu ft

Development

The Hewett field has been developed through a number of offshore installations.[4][5]

Hewett gas field installations
Installation Location Block Facility Function Type Legs Well slots Installed Production start Production to
Hewett 52/5 A 52/5 Platform Drilling & production Steel jacket 8 8 September 1967 September 1969 FTP
Hewett 48/29 A 48/29 Platform, bridge linked to FTP Drilling & production Steel jacket 12 8 May 1968 July 1969 FTP
Hewett 48/29 B 48/29 Platform Drilling & production Steel jacket 8 8 August 1972 1973 FTP
Hewett 48/29 C 48/29 Platform Drilling & production Steel jacket 8 8 1976 1976 FTP
Hewett FTP 48/29 Platform, bridge linked to 48/29 A Field terminal platform Steel jacket 8 – 1968 July 1969 Bacton
Hewett 48/29 Q 48/29 Platform, bridge linked to 48/29 A Accommodation Steel jacket 4 – – –
Other fields producing via Hewett
Deborah 48/30 Subsea Production Subsea wellhead – 1 1979 1979 48/29 C
Little Dotty 48/30 Subsea Production Subsea wellhead – 1 1979 1979 48/29 A
Della 48/30 Subsea Production Subsea wellhead – 1 1988 November 1988 48/29 A
Delilah 48/30 Subsea Production Subsea wellhead – 1 48/29 A
Area B 48/30 Subsea Production Subsea wellhead – 1 FTP
Dawn 48/29 Subsea Production Subsea wellhead – 1 48/29 C
– 48/30 & 30/10 Subsea Production Subsea wellhead – 2 48/29 C

Production

The annual gas production from the Hewett field (in million standard cubic feet) was:[4]

Decommissioning

In 2020 Eni submitted to the UK Government a proposal for the decommissioning of the Hewett field and its installations.[6] Production from Hewett ceased in 2021.[7]

See also

References
  1. Department of Trade and Industry (1994). The Energy Report. London: HMSO. pp. 41, 56, Map 10. ISBN 0115153802.
  2. Tiratsoo, E. N. (1972). Natural Gas: A Study. Beaconsfield: Scientific Press Limited.
  3. Eni (2019). "HEWETT PLATFORMS DECOMMISSIONING PROGRAMME" (PDF). gov.uk. Retrieved 25 September 2021.
  4. OPL (1985). The North Sea Platform Guide. Ledbury: Oilfield Publications Limited. pp. 315–324.
  5. Hewett Field Schematic, Phillips Petroleum Company, 2000
  6. Eni (2020). "Hewett Installations decommissioning" (PDF). gov.uk. Retrieved 26 September 2020.
  7. Oil and Gas Authority. "Daily production data". gov.uk. Retrieved 27 September 2021.
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