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Proof of concept put into practice on Greensand carbon capture project

Proof of concept put into practice on Greensand carbon capture project

March 28, 2023

A landmark Carbon Capture and Storage (CCS) project, supported by Elemental Energies’ engineering team, reached a major milestone after carbon dioxide (CO2), captured in Belgium, was injected beneath the seabed of the Danish North Sea. It was the first time that cross-border offshore CO2 storage had been undertaken.

Elemental Energies’ team has been working on the Greensand Project, led by INEOS and Wintershall, since 2022. It has been leading the conceptual well design assessment for the conversion and repurposing of the Nini West and Nini Main wells for CCS and, most recently, updated the approach to reflect technical advances, ahead of a final investment decision for full commercialisation.

The announcement this month that the first CO2 had been safely and successfully injected into the seabed beneath the Danish North Sea brought a full-scale project a step closer.

Nick Low, Elemental Energies’ Principal Drilling Engineer, explains that while the company’s involvement is just one part of a major development, helping the client understand and minimise the risks has been key to the project’s progress.

The viability of carbon capture, utilisation, and storage (CCUS) has transformed in recent years. Even just five years ago, it was considered in its infancy. Today, while there is still a long way to go, there are already more than 27 operational large-scale carbon capture and storage facilities around the world. Elemental Energies’ team has had the privilege of supporting the technical development of a number of these.

The successful injection of CO2 captured at an INEOS Oxide site in Belgium and safely stored in its Nini West oil field in the Danish sector of the North Sea is not only a huge success for all those involved but will also help build the case for future CCUS schemes around the world.

Elemental Energies’ engineering team has been supporting the consortium to update its original DNV-certified proof of concept, ahead of a Final Investment Decision for full commercial operations.

Our latest scope of work has focused on finalising the proof of concept for the conversion of three wells for CO2 injection, the decommissioning of seven other wells, and an assessment of the abandonment status/well barrier integrity of the original four exploration wells, to ensure their suitability for the use of the Nini fields as a future storage of CO2.

The main challenges

Unknown pressure limits: When these wells were constructed CCS did not exist and hence was not considered in the design process. Consequently, one of our primary focuses has been to recalculate the pressure limits of the well, verify the existing well barriers, and determine if additional well barriers are required, to minimise the risk of leakages into the subsurface, sea, or atmosphere.

Batch injection vs continuous injection: while most CCS projects involve CO2 being transported to the well via a pipeline, the Greensand project could ship tanks of CO2 to the field. This would see the gas injected into the well in batches. The impact of multiple start-ups and shut-downs on well integrity needed to be determined.

Reactivity, temperature, and corrosion changes: There are a host of other aspects to consider such as understanding the phase behaviour of CO2 during the injection and storage conditions over the life of the project, the likelihood of interaction with water if it was to leak, how to mitigate potential temperature swings during start-up and shutdown, corrosion risks.

Well interventions, final abandonment: Well Life Cycle Integrity Management considerations, as with regular oil and gas wells, must still be factored into the overall assessment and safeguarding the project. The inherent nature of CO2 also brings its own challenges both when any well interventions may be required during the injection and storage period and also for the eventual Nini field abandonment.

The Greensand Project has the potential to lock away between 0.45 to 1.45 million tonnes per year by late 2025-26, in a sandstone reservoir on the Nini field, 1,800m below sea level. By the end of 2030, this could climb to up to 8 million tonnes of CO2 per year – more than 13% of Denmark’s total annual emissions.

While technical well expertise is critical to the successful delivery of CCS projects such as Greensand, the complexities of sequestering CO2 and the implications for existing infrastructure require a unique combination of experienced multi-discipline engineers with both hydrocarbon wells and low carbon experience.

Elemental Energies is a wells-focused engineering consultancy that combines unrivalled technical wells expertise with extensive energy transition and decommissioning experience. Our team is internationally recognised for its CCS expertise and has been delivering projects for more than 15 years. During that time it has regularly advised the UK Government’s Department of Energy and Climate Change and the UK’s Oil and Gas Authority. It has provided similar leading-edge support to government departments in Norway, Australia, Tunisia and the EU for a range of CCS activities including regulatory development and providing technical due diligence on project development programmes.

The team, which has conducted over 80 major CCS and CO2 EOR studies, has also supported a wide range of independent and national operating companies including BP, Gassnova, Equinor, Shell, Maersk, Korea National Oil Company, DONG, Taqa, Marathon, Petronas, Centrica, and Woodside.

Learn more about how we can help you minimise the risk of your next energy transition project. Get in touch at


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