The Tommeliten A is a trans-boundary gas and condensate field straddling the Norwegian and the UK waters of the North Sea. Photo credit: ConocoPhillips.
The Tommeliten A will be a subsea development tied back to the Ekofisk complex. Photo credit: ConocoPhillips.
The Tommeliten A field development plan was submitted to the Norwegian and the UK authorities in November 2021. Photo credit: ConocoPhillips.

The Tommeliten A (Tommeliten Alpha) is a gas and condensate field planned to be developed in the North Sea. It is a trans-boundary field, which is primarily located in the Norwegian sector but extends into the UK waters of the North Sea.

ConocoPhillips Skandinavia, a subsidiary of ConocoPhillips, is the operator holding 28.14% stake in the Tommeliten A field development.

The other partners are PGNiG Upstream Norway (42.2%), TotalEnergies EP Norge (20.14%), Var Energi (9.09%), ConocoPhillips (U.K.) Holdings (0.21%), TotalEnergies UK (0.15%) and ENI UK (0.07%). PGNiG Upstream Norway picked up 42.2% stake in Tommeliten A from Equinor in December 2018.

The project partners submitted a plan for development and operation (PDO) of the Tommeliten A field to the Norwegian Ministry of Petroleum and Energy and the UK Oil and Gas Authority in November 2021.

Subject to approval from both the regulatory bodies, the Tommeliten A field will be developed as a subsea tieback to the Ekofisk complex in the Norwegian North Sea, with an overall investment of NOK13bn (£1.12bn) ($1.52bn). The offshore gas condensate field is expected to come on stream in 2024.

Location, discovery and reservoir details

The Tommeliten A field extends from block 1/9 on the Norwegian continental shelf (NCS) into block 30/20 of the UK North Sea.

The subsea development will be located in 75m-deep waters in the southern part of the Norwegian North Sea, approximately 25km south-west of the Ekofisk complex, which is also operated by ConocoPhillips Skandinavia.

The Tommeliten A field was discovered by Statoil (now Equinor) in 1977. It was further appraised by three more wells, namely 1/9-2, 1/9-3 and 1/9-7. The 1/9-7 wildcat well was the last well to be drilled on the discovery in 2003.

The field’s reservoir contains gas and condensate in chalk layers of the Paleocene Ekofisk and Upper Cretaceous Tor Formations, approximately 3,000m beneath the seabed.

The Tommeliten A field is estimated to hold up to 180 million barrels of oil equivalent (Mboe) resources, with gas condensate accounting for a major proportion of the recoverable resources.

Tommeliten A field development details

The Tommeliten A field development plan includes drilling ten horizontal production wells, two subsea manifolds with six slots each, and a 30km-long and 14in-diameter electrically heated flowline to send the wellstream to the Ekofisk complex for processing and export. An umbilical will also be laid from the Ekofisk complex to the Tommeliten A subsea infrastructure.

The project will also include the installation of a new processing module at the Ekofisk complex to handle additional production from Tommeliten A.

Gas will be transported through the Norpipe gas pipeline to Emden, Germany, while oil and wet gas will be exported through the Norpipe oil pipeline to Teeside in the UK.

The first two production wells of the Tommeliten A field are expected to commence production in the first half of 2024.

Topside modifications at Ekofisk

As part of the Tommeliten A field development, a new processing module will be installed on the Ekofisk 2/4 M production and process platform, while minor modifications will be carried out on the Ekofisk 2/4 J processing and transportation platform, and the Ekofisk 2/4 Z wellhead platform.

Contractors involved in Tommeliten A field development

Aker Solutions was awarded a topside modification contract worth NOK1.2bn (£100m) ($138m) for the Tommeliten A subsea development in September 2021.

The contractual scope includes engineering, procurement, construction, and installation (EPCI) works for topside modifications on certain Ekofisk installations. The contract is expected to be executed by the end of 2023.

The EPCI contract followed a NOK130m (£10.7m) ($13.8m) front-end engineering and design (FEED) contract awarded to Aker for topside modifications on the Ekofisk installations in October 2020.

Separately, Aker Solutions also won a contract worth NOK1.2bn (£99m) ($127.5m) to provide the subsea production system for the Tommeliten A field development in October 2020.

The contractual scope includes ten vertical subsea trees, two manifolds, wellheads, satellite structures, along with control systems and tie-in equipment.

Prosafe, a semi-submersible accommodation service provider based in Norway, received a NOK125m (£10.4m) ($13.6m) contract in October 2020 to provide accommodation support on the Ekofisk field to facilitate the tie-in of the Tommeliten A development.

Prosafe will deploy either the Safe Boreas or the Safe Zephyrus semi-submersible accommodation vessel for the project in the second quarter of 2022. The firm duration of the contract is 90 days.