The Stena Don rig was used to drill the first development well of the Evelyn field in 2021. Credit: Stena Drilling Ltd.
The EV1 well will be tied back to the FPSO Triton. Credit: Tailwind Energy Ltd.
Evelyn will be developed in two phases. Credit: Tailwind Energy Ltd.

The Evelyn oil field is being developed in block 21/30f within licence P1792 in the Central North Sea, UK.

The oil field is part of the Triton cluster and is owned by Tailwind Energy, an oil and gas company based in the UK.

Tailwind Energy acquired the Triton cluster from Shell UK, Shell EP Offshore Ventures, and Esso Exploration and Production UK in September 2018. Through the acquisition, it became the 100% operator of the P1792 license, which includes the Evelyn and Belinda discoveries. Shell UK and Shell EP Offshore Ventures are subsidiaries of Shell, while Esso Exploration and Production UK is a subsidiary of ExxonMobil.

The Oil and Gas Authority (OGA) permitted the development of phase one in February 2021. Tailwind Energy made the final investment decision (FID) for the project in the same month.

First oil from the field is expected to be achieved in the fourth quarter (Q4) of 2022.

The field has an anticipated life of eight years, with potential for further extension provided the life of the Triton floating production storage and offloading (FPSO) unit is extended beyond 2031, which is the current planned date for its production cessation.


The subsea oil and gas development is located in block 21/30f, 165km east of Aberdeen and 92km west of the median line between the maritime waters of the UK and Norway.

The water depth in the block is estimated to be about 95m.

Evelyn oil field discovery and exploration details

The offshore field was discovered in 1984 by the 21/30-12 exploration well in block 21/30f. The exploration well confirmed an oil rim with a gas cap.

The discovery was appraised using the 21/30-16 well in 1990, which found oil and water in Tay sands.

A single horizontal hydrocarbon development well named EV1 was completed in October 2021. Stena Don, a harsh environment semi-submersible drilling rig, was used to perform the drilling. The well flowed at 10,000 barrels a day.

Evelyn oil field development details

Dana Petroleum, an oil and gas exploration and production company, is providing support for the subsea and topsides work of the Evelyn project.

The field will be developed together with the Gannet East expansion project. It is planned to be implemented in two phases through the drilling of two new wells.

Under phase one, the EV1 well will be tied back to the Triton FPSO using a subsea pipeline. The Triton FPSO is the nearest processing facility in the area.

The subsea development will include the trenching and burial of a new 7.14km-long, 8in-diameter rigid subsea production pipeline and 7.14km-long, 3in-diameter gas lift pipeline. Using flexible spools, the two pipelines, which will be piggybacked, will be tied back to the new GEEBB (Gannet East, Evelyn, Belinda and Bittern) manifold and trees.

A 385m-long, 10in-diameter production jumper will be installed to link the GEEBB manifold to the P1 riser base at the Triton FPSO.

Dana will replace the existing Triton P1 riser with a new 9in riser during a shutdown of Triton in 2022. A new 4in gas lift jumper will also be installed between the existing Triton gas lift riser base structures and the GEEEB manifold.

A new umbilical between Triton and the Evelyn field will be installed and tied back to an existing upper riser balcony (URB) at the FPSO. A new valve skid is proposed to be installed near the EV1 well for the tie-ins of the 8in production pipeline and 3in gas lift pipeline.

Production from the well will enter the Triton production system through an existing riser and the GEEBB manifold.

Production fluids from Evelyn and Bittern will be co-mingled before being transported to the FPSO.

Oil and gas export

Oil produced from the FPSO will be exported using shuttle tankers, while the produced gas will be used to power the FPSO operations as well as for gas lift purposes. Additional gas will be transported through an existing pipeline linked to the Fulmar pipeline and exported to the St Fergus Gas Terminal, which is located onshore in Aberdeenshire, Scotland.

Phase two development

The second well, EV2, will form part of the second phase of the Evelyn field development and is subject to the success of EV1 in 2024. The future EV2 well development is expected to include drilling as well as installation of subsea infrastructure, including a new 10in pipeline, 4in gas lift pipeline, and umbilical between EV2 and the Evelyn valve skid.

Triton FPSO details

Commissioned in 2000, the Triton FPSO is located 193km east of Aberdeen in block 21/30.

It is operated by Dana Petroleum with a 52% interest. The remaining interest is owned by Tailwind Energy (46%) and Waldorf Production (2%).

The FPSO is the host processing hub for production from the Triton cluster oil fields, which include Bittern, Gannet E, Clapham, Guillemot West and Guillemot North-west, Pict, and Saxon.

Contractors involved

In September 2018, Tailwind Energy awarded a contract to Petrofac, a global energy services provider, to serve as the well operator for the Evelyn, Belinda and Gannet E licence areas for five years.

Petrofac subcontracted Stena Drilling to use the Stena Don rig to perform drilling in January 2021.

TechnipFMC, an oil and gas technology company based in the US, was contracted by Dana Petroleum to provide subsea services for the Triton FPSO in April 2015. The contractual scope included the installation of two flexible risers, fabrication and installation of an umbilical riser, removal and recovery of existing assets, and repair and maintenance works.

The company also received a contract to provide subsea engineering, procurement, installation, and commissioning (EPIC) services for the combined Evelyn and Gannet E expansion project.