The Anasuria Cluster is located in the Central North Sea, UK. Credit: catmoz / Pixabay.
The GUA‐P1 sidetrack well was drilled using the Stena Spey rig. Credit: Stena Drilling.
Crude oil produced from the fields is transported by shuttle tankers. Credit: outgunned21 / FreeImages.

The Anasuria Cluster, located approximately 175km east of Aberdeen in the Central North Sea, UK, incorporates the Teal, Teal South, Guillemot A and Cook fields, all of which share the Anasuria floating production, storage and offloading (FPSO) host platform.

The cluster of oil and gas fields is owned and operated by Anasuria Operating Company (AOC), a 50:50 joint venture (JV) between Hibiscus and Ping Petroleum. The JV acquired the project from Shell UK, Shell EP Offshore Ventures and Esso Exploration and Production UK (ESSO) in March 2016.

The JV has a 100% ownership in the Teal, Teal South, Guillemot A fields, and the Anasuria FPSO, as well as a 38.6% in the Cook field. The remaining 61.345% share in the Cook field is held by Ithaca Energy.

Production from the cluster had commenced in 1996 following the installation of the FPSO that year. The water depth within the project site is approximately 94m.

Geology and reserves

The main reservoir within the Anasuria Cluster is the Upper Jurassic Fulmar Formation, followed by the Triassic Skagerrak Formation, the Palaeocene Forties Formation and the Upper Jurassic Heather Formation sandstones.

As of July 2018, the Anasuria Cluster of fields were estimated to hold combined proved and probable (2P) reserves of 24.2 million barrels (MMbbl) of oil and 17.5 billion standard cubic feet (Bscf) of gas.

The 2C oil resources are estimated to be 7.8MMbbl of oil and 6.7Bscf of gas.

Anasuria Cluster development details

AOC plans to extend the production life of the area by an additional 20 years through workovers, infill drilling activities, upgrade of existing water injection facilities, installation of new water injection facilities and tie-in with neighbouring facilities, including the Kite field, which was discovered in 1993.

Located in Blocks 21/35 and 21/30, The Guillemot A oil and gas field was discovered in 1979 and started production in 1996. It is the largest field within the cluster and integrates five producer wells and a water injection well.

The Guillemot A field saw the drilling of the GUA-P2 sidetrack well in 2018, followed by the drilling of the GUA‐P1 sidetrack well in 2019 to unlock 1.7MMbbl of oil in the cluster. The work was completed by Stena Spey rig in August 2019 and the well flowed at a rate of 1,800 barrels per day (bpd).

As northernmost field within the cluster, the Cook oil and gas field is located at Block 21/20a. It was discovered in 1983 and started production in 2000 through a single well.

The Teal oil and gas field at Block 21/25 started production in 1997 through one production well and integrates two water injection wells.

The Teal South oil and gas field at Block 21/25 started production in 1996 through a producer well and integrates a water injection well. The field was shut down in 2012 due to hydrogen sulphide (H2S).

Crude oil produced from these fields is transported by shuttle tankers, while gas is exported by the Fulmar gas pipeline to St Fergus gas terminal in Aberdeenshire.

Anasuria FPSO

The Anasuria FPSO is installed within Block 21/25, between the Teal and Teal South fields. Shell’s first purpose-built FPSO facility to be installed in the North Sea, it is fixed to the seabed by a turret mooring system at a water depth of approximately 89m.

FPSO’s primary separation and processing facilities include two first-stage separators, a second-stage and a third-stage separator, two HP water injection pumps and seven oil cargo tanks with a storage capacity of 20,000 million standard cubic metres (MMscm) each. The platform further incorporates three gas compressors and has a designed processing capacity of 11,000m³/d.

The vessel weighs 125,000t and is equipped with a main control room, a switchgear module and a helideck.

Contractors involved with the Central North Sea offshore oil and gas project

The JV contracted Petrofac to provide operations services for the FPSO, as well as monitor and manage the pipelines and wells for 100% of the owned fields within the cluster for five years beginning in 2016.

Contractors involved with the development of the Anasuria FPSO include SBM Offshore as the main contractor, Stork Protech as the topsides engineering subcontractor, and Mitsubishi Heavy Industries (MHI) as the barge subcontractor.

Amec implemented the fabrication and installation of 22 topside processing facilities weighing approximately 3,500t, whereas the strength and fatigue assessments for the FPSO were conducted by Babcock International.

The mooring installation works were performed by Aker / Heerema, the installation of tie-backs, flexible risers and the Fulmar pipeline tie-in was conducted by McDermott, and the subsea facilities were installed by Cooper Oil Tools.