Eni North Sea carbon storage plans advanced significantly in 2025 as the company drilled an appraisal well at the Hewett field — one of the UK Continental Shelf’s longest-serving gas producers — to assess its COâ‚‚ storage potential. The well, drilled by the Valaris 72 rig from May 2025, marks the first appraisal drilling on acreage awarded in the world’s first large-scale carbon storage licensing round, and signals the start of a formal transition from gas extraction to carbon sequestration at the site.
End of an Era: Hewett Field Shuts Down After 56 Years
Located 22 kilometres off the Norfolk coast, the Hewett field produced 3.5 trillion cubic feet of gas before its permanent shutdown in 2023. The field has since entered lighthouse mode — assets uncrewed and non-operational, but not yet decommissioned. Petrofac served as duty holder and offshore installation manager through to shutdown, with its final crew departing on the last flight from the platform.
Petrofac will remain duty holder and pipeline operator until full decommissioning is complete. Offshore contractor Scaldis has removed three of the six platforms, with the Central Complex scheduled for removal in 2026. The end of production at Hewett closes a chapter that began in 1969 — a period that saw the field help underpin UK gas supply for over half a century.
Bacton CCS Project: Eni’s Carbon Storage Plans for Hewett
Eni’s subsidiary Bacton CCS Limited holds License CS008, one of 21 awarded in the UK’s inaugural carbon storage licensing round in September 2023. The Bacton CCS project targets large-scale COâ‚‚ storage capacity linked to the UK’s southern North Sea gas infrastructure, using existing pipelines and wells to reduce development cost and timeline. The appraisal well extracted 270 feet of core and conducted a nitrogen injection test before being plugged and abandoned — providing the subsurface data needed to determine long-term injection feasibility.
In May 2025, Eni announced an exclusivity agreement to sell a 49.99% stake in Eni CCUS Holding to Global Infrastructure Partners (GIP), with a definitive deal finalised in August. The partnership strengthens the financial backing for Eni’s UK CCS ambitions and is consistent with the broader European momentum in carbon management infrastructure. The strategic case for underground storage as a long-term energy system asset is examined in OGSN’s 2026 underground gas storage outlook.
UK Carbon Storage Capacity and NSTA’s Role
The North Sea Transition Authority estimates that the UK Continental Shelf has capacity to store up to 78 gigatonnes of COâ‚‚ — enough to offset all emissions produced in the UK since the Industrial Revolution. This geological potential underpins the UK’s ambition to position itself as a global leader in carbon capture and storage, repurposing depleted hydrocarbon reservoirs and existing offshore infrastructure.
Andy Brooks, NSTA Director of New Ventures, described the Hewett appraisal well as a significant milestone for the sector, noting that it represents the first drilling on acreage from the inaugural licensing round. The NSTA continues to work with licensees across the 21 awarded carbon storage licences to progress appraisal and development plans. For context on the UK’s wider energy security position, see OGSN’s analysis of UK energy security and strategic storage.
North Sea CCS: A Growing Asset Class
Hewett joins a growing list of North Sea assets transitioning from fossil fuel production to carbon sequestration, alongside projects at Goldeneye, Endurance, and Ravenna. The repurposing model — using depleted reservoir geology and existing offshore infrastructure to reduce CCS capital cost — is becoming a standard development pathway across the UK and Norwegian sectors.
For Eni, the Bacton CCS project is part of a wider CCUS portfolio that spans the UK, Italy, and North Africa. The company’s decision to bring in a major infrastructure investor at the holding company level signals confidence in long-term revenue from COâ‚‚ storage — a market still in early commercial development but with regulatory frameworks now established in the UK, EU, and Norway. The scale of LNG and gas infrastructure investment shaping the broader North Sea transition is covered in OGSN’s 2026 LNG storage infrastructure analysis.
What is Eni’s North Sea carbon storage project at Hewett?
Eni’s Bacton CCS project plans to repurpose the depleted Hewett gas field as a large-scale COâ‚‚ storage site. Through its subsidiary Bacton CCS Limited, Eni holds License CS008 awarded in the UK’s first carbon storage licensing round. An appraisal well was drilled in 2025 to assess the field’s injection potential.
How much gas did the Hewett field produce before shutdown?
The Hewett field produced 3.5 trillion cubic feet of gas over its 56-year operating life before permanently shutting down in 2023. Located 22 kilometres off the Norfolk coast, it was one of the UK Continental Shelf’s longest-serving gas producers, first coming online in 1969.
What is the UK’s total carbon storage capacity in the North Sea?
The North Sea Transition Authority estimates the UK Continental Shelf has capacity to store up to 78 gigatonnes of COâ‚‚ — equivalent to all emissions produced in the UK since the Industrial Revolution. This capacity is central to the UK’s ambition to become a global leader in carbon capture and storage.
Who is financing Eni’s UK CCS programme?
In 2025, Eni agreed to sell a 49.99% stake in Eni CCUS Holding to Global Infrastructure Partners (GIP), bringing in major infrastructure investment to support its UK and wider European carbon storage development. The deal was finalised in August 2025.
Which other North Sea fields are being converted to carbon storage?
Several North Sea fields are following a similar repurposing pathway, including Goldeneye, Endurance, and Ravenna. These projects use depleted reservoir geology and existing offshore infrastructure to reduce development costs, making the North Sea one of the most strategically significant regions globally for large-scale CCS deployment.