Valhall field is located in the southern part of the Norwegian sector of the North Sea at water depth of 70m. The site is close to the Danish and UK borders.
Discovered in 1975, Valhall began production in 1982.
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Aker BP holds the operatorship along with a 90% stake in the offshore field. The remaining 10% stake is with Pandion Energy.
Originally, Valhall was expected to produce around 250 million barrels of oil equivalent over its life. However, it has produced more than 1.1 billion barrels as of October 2022.
Aker BP aims to produce an additional billion barrels of oil equivalent by 2050. Redevelopment and modernisation work are underway to extend the life of the field.
The Valhall Flank West project in the western flank of the Valhall oilfield began production in 2019, while plan for development and operation for Hod development was submitted in 2020.
Development
The Valhall field was discovered by Amoco Norway in 1975 by drilling the 2/8-6 discovery well.
The initial plan for development and operation (PDO) was approved in 1977.
It was developed with three facilities for accommodation (QP), drilling (DP), and processing and compression (PCP), with production commencing in 1982.
In 1995, a PDO for a wellhead facility (WP) was approved, followed by a water injection platform (IP) in 2000. The platforms were connected with bridges.
The PDO for two wellhead platforms on the northern and southern flanks was green lighted in 2001, while the redevelopment PDO secured approval in 2007.
The redevelopment plan included building an accommodation and processing platform (PH) at the field as part of a process to replace ageing facilities.
The scope of the redevelopment included installation of the platform mounted on a fixed steel jacket, an external system of bridges linking the new platform to the existing complex, a power-from-shore system, as well as an integrated operating environment connecting onshore and offshore personnel.
Additionally, it involved the delivery of two unmanned flank platforms, located around 6km away from the main facilities.
The Valhall Flank West PDO was approved in 2018 and production commenced a year later in 2019.
Currently, the project features five topsides and around 50 active wells.
Reservoir and recovery
Valhall field produces from the chalk rocks in the Upper Cretaceous Tor and Hod formations at a reservoir depth of approximately 2,400m.
The field began production with pressure depletion and compaction drive, while water injection in the centre of the asset began in 2004. In most of the wells, gas lift is used to optimise production.
Aker BP has also used a new well stimulation method called ‘Single-Trip Multi-Frac’ at the Valhall field. The method, primarily used onshore to produce shale oil, will reduce well costs.
The stimulation is carried out by creating fractures in the reservoir, by high-pressure pumping in sand mixed with a fluid system into the reservoir to improve flow.
From the Valhall field, Oil and Natural Gas Liquids are transported through a pipeline to the Ekofisk field and then to Teesside in the UK. It exports gas using Norpipe to Emden in Germany.
Infrastructure
The Valhall area consists of a field centre with five platforms- an accommodation and processing platform (PH), a drilling platform (DP), a processing and compression platform (PCP), a wellhead platform (WP) and a water injection platform (IP) connected by bridges, and four wellhead platforms that are remotely controlled from the field centre.
Since 2013, Valhall field is fully powered from shore via a 294km submarine cable from Lista. The direct current (DC) electricity received is converted to alternating current (AC) to power everything from heavy machinery to cabin lights.
The electrification reduced carbon dioxide emissions by more than 300,000 tonnes, and nitrogen oxide emissions by 250 tonnes from the field centre.
In 2021, several wells were drilled at the site.
Contractors involved
ABB continued as a project partner after it was decided to refurbish and upgrade Valhall’s production infrastructure to continue production until 2050. The company was responsible for Valhall’s automation and telecoms systems from the design stage.
French firm Nexans manufactured, delivered and installed 292km of HVDC (High Voltage Direct Current)-IRC subsea cable and a separate fibre-optic subsea cable to enable the offshore field secure power from shore. Nexans also delivered associated equipment at the shore and on the Valhall complex.
Hitachi Energy was responsible for system engineering, including the design and supply of the HVDC Light converter stations.
Allseas secured a call-off award for the removal and disposal of Valhall DP- PCP- and Hod topsides and jacket installations in the period from 2021 to 2026.
In December 2021, Aker Solutions won front-end engineering and design (FEED) contracts from Aker BP for the Valhall field as well as for the King Lear discovery.
The scope of the FEEDs includes a new central platform (NCP) featuring a nearly 12,000 metric-tonne topside, a 7,500 metric-tonne steel jacket substructure and a bridge of more than 1,000 metric tonnes.
The NCP will become the central hub and production platform on the Valhall field replacing older infrastructure.
In August 2022, Rosenberg Worley received a letter of intent (LOI) regarding the construction of two modules for the NCP.
