Tolmount

Location and Geology

The Tolmount gas field is located in Block 42/28d of the P1330 license, approximately 40 km east of the Yorkshire coast in the southern North Sea, UK. It is also about 36 km from the nearest UK coastline at Flamborough Head and 156 km from the UK/Norway median line.
The field is situated in the Lower Leman Sandstone Formation Play Fairway, characterized by Aeolian dunes, fluvial sands, and local sabkha. The reservoir is linear with parallel faulting.

The project is jointly owned by Harbour Energy (50%) and Dana Petroleum (50%). Harbour Energy operates the field, having inherited the operatorship through the merger of Premier Oil and Chrysaor in 2021. Previously, E.ON E&P had farmed into the project in 2010 and later sold its UK E&P assets to Premier Oil in April 2016.

The Tolmount field was first discovered in 2011 and appraised with the drilling of two appraisal wells, 42/28d-13 and 42/28d-13z, in 2013. These wells confirmed the presence of high-quality hydrocarbons.
The development plan involves a standalone normally unmanned installation (NUI) with a minimum facilities platform (MFP) supporting four development wells. The platform includes 1,456-tonne topsides and six slot facilities installed at a water depth of about 52 meters.
The produced gas and condensate are exported to shore via a new 48 km long, 20-inch diameter gas pipeline and a piggybacked 3-inch methanol pipeline. The pipeline system connects to the Dimlington gas terminal or the Humber Gathering System (HGS) for the Tolmount East field.
First gas from the Tolmount field was achieved in April 2022, and the Tolmount East field came online in December 2023. The Tolmount area has a production capacity of 13,000 barrels of oil equivalent per day.

The Greater Tolmount Area is estimated to contain up to one trillion cubic feet of gas. The main Tolmount field contains approximately 540 billion cubic feet, while the Tolmount East and Tolmount Far East fields are estimated to hold 220 billion cubic feet and 150 billion cubic feet of gas, respectively.
The peak production capacity of the Tolmount Main gas field is expected to be up to 300 million standard cubic feet per day (mmscfd).

The development required an Environmental Statement (ES) due to the production exceeding the 500,000 m3 EIA Directive threshold. The ES identified potential environmental impacts such as physical presence, seabed disturbance, discharges to sea, atmospheric emissions, underwater noise, and accidental events. After review, OPRED concluded that the project would not have a significant adverse impact on the environment.

Rosetti Marino was awarded the engineering, procurement, construction, installation, and commissioning (EPCIC) contract for the platform. The construction and installation of the jacket and topsides were completed by Heerema's semisubmersible crane vessel Sleipnir in October 2020.
Costain and Wood Group provided front-end engineering design (FEED) services for the subsea pipeline and the overall project, respectively. Saipem was subcontracted for pipeline EPCI works.
An infrastructure joint venture between CATS Management and Dana Petroleum owns and pays for the platform and pipeline, with upgrades to the onshore terminal. Premier Oil (now Harbour Energy) pays a tariff for the transportation and processing of the gas.

Premier Oil (now Harbour Energy) secured an innovative financing structure for the project, minimizing capital expenditure while maintaining exposure to the upside in the Greater Tolmount Area. Premier’s share of the capital expenditure was $120 million, covering project management and development drilling costs.

The Tolmount East field, which is a tie-back to the Humber Gathering System, started production in December 2023. This field was drilled in 2019 and is expected to produce around 150 billion cubic feet of gas.
Harbour Energy is also involved in other North Sea projects, including the Talbot and Leverett fields, which are in various stages of development and appraisal.