North Sea field closing 56-year gas chapter as Eni explores its CCS future

October 17, 2025, by Dragana Nikše

Italy’s oil and gas giant Eni has drilled an appraisal well for a depleted field in the UK sector of the North Sea to assess its potential for carbon capture and storage (CCS).

As disclosed in a social media post by Petrofac, 56 years after production from the Hewett field began, the company’s last operational team left the platform on their final flight. This marked the start of what is known as ‘lighthouse mode’ phase for the Hewett complex, denoting an asset that is no longer crewed or operational but not yet removed.

David Williamson, Offshore Installation Manager for the Hewett field, commented: “It was an honour and privilege to lead Petrofac’s fantastic team to this milestone, along with my back-to-back Dave Alger. As with every ultra-late-life asset, there were numerous challenges to overcome along the way, but with the willingness and proactive approach from all involved, both on and offshore, the project was brought to a safe conclusion.”

Although this marks the end of Petrofac’s work manning the assets, the company will remain the duty holder and pipeline operator until the platforms have been dismantled.

Situated 22 kilometers off the Norfolk coast, Hewett was one of the UKCS’s longest-serving gas fields. In production since 1969, it is described as only the third North Sea field to reach this stage, after West Sole and Leman. The field had produced 3.5 trillion cubic feet of gas by the time it permanently shut down in 2023.

The decommissioning project for the field’s six platforms is halfway done. Three abandoned platforms have been dismantled and removed by Scaldis, while the remaining three platforms, forming the Central Complex, are scheduled for removal next year.

However, this is not the end for the gas field, which is getting a new lease on life. Its depleted reservoirs are set to underpin Eni‘s Bacton CCS project. As reported by the North Sea Transition Authority (NSTA), the first appraisal well on the Hewett field was recently drilled.

The appraisal well is seen as an important step towards assessing the carbon storage potential of the UK continental shelf (UKCS). The NSTA believes the basin has up to 78 gigatonnes of potential storage capacity in depleted reservoirs and saline aquifers, which it says is enough to sequester all the CO2 emitted in the UK since the industrial revolution.

The NSTA further stated that Eni contracted the Valaris 72 rig to drill the well, with work starting in May 2025. Extensive data sampling was conducted, including cutting 270 feet of core and performing a nitrogen injection test, before plugging and abandoning it.

Andy Brooks, NSTA Director of New Ventures, said: “The appraisal well on Hewett – the first to be drilled on acreage awarded by the NSTA as part of the world’s first large-scale carbon storage licensing round – is yet another important milestone for the sector as it looks to assess further stores which should progress towards development. The NSTA continues to work with licensees to ensure that their plans are the right ones.”

The UK regulator offered 21 licenses in the UK’s inaugural carbon storage licensing round, which concluded in September 2023. License CS008, which covers Hewett, is held by Bacton CCS Limited, a subsidiary of Eni CCUS Holding.

In May, Eni announced having signed an exclusivity agreement for the sale of a 49.99% stake in Eni CCUS Holding to Global Infrastructure Partners (GIP). A definitive agreement followed suit in August.