Tartan oil field
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| Tartan oil field | |
|---|---|
  Location of Tartan oil field | |
| Country | United Kingdom |
| Region | North Sea |
| Location/blocks | 15/16a and 14/20a |
| Offshore/onshore | Offshore |
| Coordinates | 58°22′11″N 00°04′25″E / 58.36972°N 0.07361°E |
| Operators | Repsol Resources UK |
| Owner | Repsol Resources UK |
| Field history | |
| Discovery | February 1975 |
| Start of production | January 1981 |
| Abandonment | 2020 |
| Production | |
| Estimated oil in place | 14.1 million tonnes (~ 12.8×106 m3 or 80.5 million bbl) |
| Recoverable oil | 62 million barrels (~1.1×107 t) |
| Producing formations | Upper Jurassic sandstone |
The Tartan oil field is a significant crude oil producing field in the UK sector of the North Sea, 187 km north-east of Aberdeen. Production of oil started in 1981 and ceased in 2020, the Tartan Alpha installation is currently (2021) undergoing decommissioning.
The Tartan oil field is located in Blocks 15/16a and 14/20a of the UK North Sea continental shelf. Its name continues the Scottish theme of oil fields in the area (eg Claymore, Piper, Scott).[1] The Tartan field was discovered in February 1975 and the oil reservoir comprises an Upper Jurassic sandstone at a depth of 9,800 to 12,000 feet (2,9873 to 3,658 metres).[2] The reservoir and its fluids had the following characteristics:[2]
| Parameter | Value |
|---|---|
| Porosity | 8–18 % |
| Permeability | 70–500 md % |
| API gravity | 37–40°API |
| Gas Oil Ratio | 900 standard cubic feet/barrel |
| Sulfur content | 0.7 % |
| Pressure/temperature | 4,600–5,700 psi (31,715–39,300 kPa) at 220–240 °F |
| Recoverable reserves | 62 million barrels, 14.1 million tonnes |
Owners and operators
Development
The field was developed by a single integrated drilling, production and accommodation platform: Tartan Alpha (Tartan A). The principal design data of the Tartan A platform is given in the following table.[2]
| Installation | Tartan A |
| Coordinates | 58°22’11”N 00°04’25”E |
| Water depth, metres | 142 |
| Fabrication substructure | McDermott-Hudson, Cherbourg and Methil |
| Jacket weight, tonnes | 14,400 |
| Topsides design | Lawrence Allison |
| Topsides weight, tonnes | 14,100 |
| Function | Drilling, production, accommodation |
| Accommodation (crew) | 200 |
| Type | Steel jacket |
| Legs | 4 |
| Piles | 28 |
| Well slots | 30 |
| Throughput oil, barrels per day (bpd) | 75,000 + 14,400 Natural Gas Liquids |
| Water injection, bpd | 105,000 |
| Platform installed | June 1979 |
| Production started | January 1981 |
| Oil production to | Claymore |
| Gas production to | Frigg pipeline |
Tartan Alpha was originally connected to the Piper Alpha platform through a 19 km 18-inch diameter gas pipeline. The failure of the riser of this pipeline at about 22:20 6 July 1988 during the Piper Alpha disaster led to a second major explosion followed by a widespread fire.[4]
Production from Tartan's faulted reservoir was 'disappointing'. Texaco therefore halted production well drilling on Tartan and focussed on the Highlander field, about 13 km north-west of Tartan, to enable the field to produce through Tartan.[2]
Tartan satellites
In addition to its own production several other smaller fields were tied back to Tartan. The design data is summarized below.[5]
| Name of field | Highlander | Petronella | Galley | Duart | Tartan North Terrace |
| Year installed | 1985 | 1986 | 1998 | 2007 | 2004 |
| Distance from Tartan, km | 13 | 11 | 14 | 3.4 | |
| Production pipeline, inches | 12 | 8 | 10 | 8 | 6 |
| Gas lift pipeline, inches | 8 | 12 | – | – | 3 |
| Water injection pipeline, inches | 4 | – | 8 | – | – |
| No. of Wells | 1 | 1 | 1 |
Production from the Galley field was originally through the Northern Producer a floating production facility.[6]