UKCCSRC Knowledge Exchange Conference 2025 – Parallel session 2b – CO₂ Storage (ECR Meeting Fund)

Muyang Chen (Swansea University) shares their takeaways from “Parallel session 2b – CO₂ Storage” at the UKCCSRC Knowledge Exchange Conference 2025

Ensuring Long-Term Safety in Storage Procedure

At the recently concluded UKCCSRC Knowledge Exchange Conference 2025, the long-term safety of Carbon Capture and Storage (CCS) technology emerged as a central focus. Stephen Heath, Farshad Jafarizadeh and Simon Gregory, from chemical, geophysical, and microbiological dimensions respectively, systematically articulated the potential risks across the entire CCS value chain and presented their innovative, interdisciplinary solutions, collectively providing robust support for the safety and reliability of large-scale geological sequestration projects.

Exploring Production Chemistry Risks and Mitigation Strategies for Carbon Capture, Utilisation and Storage (CCUS)

Stephen Heath’s session introduced the critical role of “Production Chemistry” in CO₂ injection and long-term storage processes. This discipline, originally applied in oil and gas extraction and processing to manage and mitigate chemical issues such as corrosion and scaling, is equally applicable to the geological sequestration phase of CCUS (Carbon Capture, Utilization, and Storage) technology. Heath emphasized that CO₂ injection and storage presents not merely physical challenges but also complex chemical and biological risks, primarily encompassing corrosion, scaling, hydrate formation, and microbial activity.

Regarding corrosion, CO₂ reacts with water to form acidic solutions, corroding metallic wellbores, cement, and reservoir minerals. The co-injection of impurities like NO₂ and SO₂ can exacerbate this degradation, leading to compromisedwellbore integrity and potential CO₂ leakage. Mitigation strategies include selecting corrosion-resistant materials (e.g., corrosion-resistant alloys, CO₂-resistant cement), utilizing models to predict corrosion rates, and injecting chemical inhibitors.

Microbial activity poses risks closely linked to corrosion: microbes can proliferate in wellbores and reservoirs, forming biofilms that accelerate corrosion by producing H₂S. They can also induce mineral dissolution or biomineralization. Solutions involve employing corrosion-resistant materials, adding biocides or H₂S scavengers, and, under controlled conditions, leveraging microbially induced precipitation to enhance sealing.

The risks associated with scaling and hydrates primarily involve flow assurance disruption due to blockage. Scaling arises from salt precipitation or carbonate deposition (e.g. halite or calcium carbonate) after CO₂ injection, obstructing wellbore pores; however, precise control of deposition location can also enhance fracture sealing and reinforcement. Hydrates are ice-like solids formed by CO₂ and water under high-pressure, low-temperature conditions. Uncontrolled formation can block wellbores, but if managed appropriately during capture and separation, hydrate formation can aid CO₂ separation and purification.

Finally, Heath concluded that mitigating these risks requires an integrated approach utilising chemical modelling, material science, chemical additives, and biological control. This not only prevents corrosion, blockage, and leakage but also can proactively enhance storage effectiveness through controlled mineralization or hydrate formation, thereby improving the long-term safety and efficiency of CO₂ injection and storage.

Time-Shift Detectability for Monitoring Fault Reactivation and Microseismicity During CO₂ Injection

Farshad Jafarizadeh’s research also focuses on enhancing the long-term safety of CCS projects, specifically targeting risks associated with fault reactivation and induced microseismicity triggered by CO₂ injection, with the aim of achieving effective monitoring and early warning. In his presentation, he detailed an analysis method based on 4D seismic data for assessing “time-shift detectability”.

The core innovation lies in the ingenious combination of the classic Geertsma and Okada geophysical models to meticulously deconstruct complex subsurface signals. By separating and integrating the signals from these two models, he was able to identify unique time-shift signal characteristics indicative of fault reactivation. This distinct feature allows researchers to effectively differentiate fault reactivation phenomena from mere pressure signals.

He further investigated the method’s detectability across various monitoring equipment and event magnitudes. Results indicate that optimal monitoring equipment (PRM) can detect time shifts of approximately 0.06 milliseconds, which, according to model calculations, corresponds to the detection of seismic events with a magnitude of 2.65 or greater.

The method’s effectiveness was validated through analysis of real-world field cases, including Aneth and Ekofisk oil fields:

• In a microseismic case from the Aneth field, research showed that while individual microseismic events might not be independently detectable, the accumulated signals from a microseismic cloud formed by numerous events could be captured.
• In a genuine strong seismic event at the Ekofisk field, actual fault reactivation produced a ‘+0.31 millisecond time-shift’ signal, which was significantly larger than the instrument’s detection limit, strongly demonstrating the practical applicability of this technology.

The UK subsurface microbial limits database: a screening tool for safe geological storage

Simon Gregory presented a systematic, data-driven framework and its implementing tool for microbial risk assessment. His work quantifies the limits of deep subsurface microbial activity, specifically assessing the impact of key physicochemical parameters (e.g., temperature, salinity, pH, pressure, permeability, porosity, and sulphate concentration) on microbial activity within deep subsurface CO₂ and H₂ storage environments. It also established clear high, medium, and low-risk thresholds for microbial activity under these parameters. This advancement transitions microbial risk assessment from qualitative understanding to a quantitative one. Furthermore, this tool features a user-friendly interactive database interface, enabling non-microbiologists, such as engineers and geoscientists, to rapidly and intuitively assess microbial risks at specific subsurface storage sites, thereby supporting decision-making.

Overall Conclusion

In summary, these three closely interconnected presentations at the conference clearly demonstrated that ensuring the long-term safety of CCS projects is a systematic engineering endeavor requiring the integration of knowledge from production chemistry, geophysics, and microbiology. From preventing well-bore corrosion and providing early warning for fault reactivation to quantitatively assessing microbial risks, each technological advancement lays a solid cornerstone for the promise of secure CO₂ sequestration.