| Sean gas field | |
|---|---|
| Country | United Kingdom |
| Region | North Sea |
| Block | 49/25 |
| Offshore/onshore | Offshore |
| Operators | Shell 1986-2015. ONE 2015- |
| Owner | Shell 1969-2015, ONE 2015- |
| Field history | |
| Discovery | 1969 |
| Start of production | 1986 |
| Production | |
| Current production of gas | 600×106 cu ft/d (17×106 m3/d) |
| Estimated gas in place | 16.4×109 m3 (580×109 cu ft) |
| Producing formations | Rotliegendes sandstone |
The Sean gas field is a small natural gas and associated condensate field located in the UK sector of the North Sea, 67 miles (108 km) off the Norfolk coast.
The field
The Sean gas field is a natural gas field located in the North Sea and comprises three accumulations North Sean, South Sean and East Sean. The field 67 miles (108 km) north-east of Bacton Norfolk and is located to the south east of the Indefatigable gas field.[1] It is named after the four partners at the time of its discovery: Shell, Esso, Allied Chemical and National Coal Board.[2] The gas reservoir is a Rotliegendes sandstone 170–290 feet (52–88 metres) thick at a depth of 8,300 feet (2,530 m). North Sean was discovered in April 1969 and South Sean in January 1970 both are located in UK Block 49/25. The original determination of the gas in place amounted to 425 billion cubic feet (12.4 billion cubic metres).[1]
Development
The Sean field has been developed through a number of offshore platforms.[1]
| Platform | Field | Function | Type | Legs | Well slots | Installed | Production start | Production to |
|---|---|---|---|---|---|---|---|---|
| Sean PP | South Sean | Production & accommodation | Steel jacket | 8 | – | May and November 1985 | October 1986 | Bacton (via 30-inch 107 km pipeline) |
| Sean PD | Drilling and wellhead | Steel jacket | 6 | 12 | January and November 1985 | October 1986 | Sean PP (bridge link) | |
| Sean PK | Compression | Steel jacket | Planned future, never installed | Sean PP (bridge link) | ||||
| Sean RD | North Sean | Satellite wellhead | Steel jacket | 6 | 12 | January and November 1985 | October 1986 | Sean PP (via 20-inch 4.7 km pipeline) |
The East Sean field has not been developed.
Production
Production from the field began in August 1986. Sean was operated as a peak shaving field with a maximum delivery of 600 MMSCFD (million standard cubic feet per day). Processing facilities comprise 3-phase separation and gas dehydration. Gas and associated condensate are transported via a 30-inch diameter pipeline to the Shell processing facility at the Bacton gas terminal, Norfolk.[2]
The specification of third party gas for entry into the export gas pipeline was as follows:[3]
| Parameter | Value |
|---|---|
| Gross calorific value | 37–44.5 MJ/Sm3 |
| Oxygen | <0.2% |
| CO2 | 2 mol % maximum |
| H2S | <3.3 ppm |
| Total sulfur | <15 ppm |
| Wobbe Index | 48–51.5 MJ/Sm3 |
| Inerts | <7% |
| Nitrogen | <5% |
In June 2015 Oranje-Nassau Energie (ONE) acquired a 50% interest in the Sean field from Shell. SSE E&P UK holds the remaining 50% interest. ONE became the operator of Sean.[4]
See also
References
- 1 2 3 Oilfield Publications Limited (1985). The North Sea Platform Guide. Ledbury: Oilfield Publications Limited. pp. 608–12.
- 1 2 Department of Trade and Industry (1994). The Energy Report. London: HMSO. p. 85. ISBN 0115153802.
- ↑ Shell, Sean Complex Infrastructure Information Fact Sheet, January 2015
- ↑ "ONE takes charge of Sean in North Sea". Offshore magazine. 2015. Retrieved 5 October 2021.