Thistle oil field

The Thistle oil field is a large oil field in the Northern sector of the North Sea. The oil field, discovered in September 1972 by Signal Oil and Gas Company, is produced over the Thistle Alpha platform, located 125 nautical miles Northeast of Sumburgh, Shetland Islands and 275 nautical miles Northeast of Aberdeen, Scotland.

Licence P236 was awarded as part of the UKCS fourth round in 1972, and the first well on the site was drilled and completed in July 1973 when the Thistle oil field was confirmed as a commercial discovery. The oil field is estimated to have a reserve of roughly 824 million barrels of oil. The nearby Deveron field, also produced over the Thistle Alpha platform, was discovered in 1972 following the successful completion of a second well on the site. A 1997 seismic re-interpretation site's estimated the reserves to be roughly 61.3 million barrels of oil.

Production commenced for partners BNOC, Britoil and BP on the site in 1978. Ownership of the operations licence for the site was subsequently transferred to DNO in 2003, followed by Lundin in 2004 before the demerging of Lundin’s UK assets in 2010, when EnQuest became the operator. The site is currently operated in partnership between EnQuest and BP, with EnQuest holding over 99% of the total ownership of the site.

The Thistle Alpha platform is a fixed installation, which consists of a 60-slot drilling and production platform. It was built at the Graythorp Dry Dock, Teesside now renamed TERRC

The jacket is a conventional steel tower structure approximately 183 meters tall with a base measuring 85 meters by 82 meters and weighs 31,500 tonnes with an integral Module Sub Frame (MSF), and is secured by steel piles driven 143 meters into the seabed. The Thistle Alpha platform was installed and completed in 1976.

The installation comprises a steel jacket with four main legs, supporting 36 modules arranged on 3 deck levels. 28 of these modules contain the equipment and machinery, which constitute the production, utilities, drilling systems and facilities. The remaining 8 modules situated on the southeast end of the installation contain living quarters (LQ), offices, the central control room (CCR), the helideck and workshops. The platform was installed on the jacket in 1978.

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