Commercial-scale carbon capture projects deploy extensive risk-based monitoring systems across atmosphere, biosphere and subsurface zones to verify permanent geological storage integrity

Effective monitoring is a cornerstone for scaling carbon capture and storage (CCS) projects, building regulatory and public trust, and supporting global climate goals by ensuring the safe and permanent storage of CO2, according to a report from the Global CCS Institute.

Monitoring plans are site-specific and tailored to address the unique risks and requirements of each CO2 storage project, with four objectives guiding operations: Quantifying CO2 stored, ensuring containment, ensuring conformance and ensuring environmental safety.

ADAPTIVE MONITORING

Shell’s Quest project exemplifies the evolution of monitoring strategies based on accumulated operational data.

After injecting 8.8 million tonnes of CO2 over nearly a decade, the project demonstrated that injected CO2 behaved precisely as predicted within the storage complex, enabling strategic optimisation of monitoring activities in 2023.

With surface leakage likelihood now minimal, Quest scaled back atmospheric and biosphere monitoring tools whilst maintaining comprehensive subsurface surveillance focused on detecting potential wellbore leakage pathways.

Time-intensive 3D seismic surveys were reduced in frequency, and costly atmospheric monitoring using eddy covariance flux systems and laser CO2 sensors was ceased entirely, demonstrating how evidence-based risk assessment enables operators to optimise resource allocation without compromising safety.

TECHNOLOGY DEPLOYMENT

Monitoring technologies span five distinct environmental zones:

• Atmospheric monitoring deploys airborne electromagnetic systems and airborne spectral imaging to directly and indirectly monitor CO2 concentrations and detect unexpected emissions, whilst satellite interferometry detects surface deformation related to CO2 plume movement in storage formations.

• Biosphere monitoring utilises eddy covariance, soil gas concentration measurements and groundwater chemistry analysis to monitor gas fluxes and detect changes in soil or groundwater chemistry indicating potential CO2 migration.

• Surface seismic imaging and gravity measurements detect subsurface changes including CO2 plume movement, density variations and potential structural shifts in storage formations.

• Subsurface monitoring employs downhole sensors measuring fluid chemistry, pressure and temperature in injection zones, enabling precise tracking of CO2 behaviour, whilst geophysical logging and seismic profiling detect changes in rock formations.

• Offshore environments deploy bubble stream detection, multi-echo soundings and seafloor gas sampling to monitor CO2 leakage and ensure integrity above storage sites.

The EU Directive 2009/31/EC Article 8 requires comprehensive site characterisation to assess potential risks, whilst ISO 27914 Section 7.4 specifies baseline monitoring requirements.

Post-closure monitoring mandates vary by jurisdiction, with EU regulations requiring, at least, 20 years of monitoring unless stability is confirmed earlier, whilst Australia’s Offshore Petroleum and Greenhouse Gas Storage Act establishes minimum 15-year closure assurance periods.