Decarbonisation Technology - November 2024 Issue

have been employed, including time-lapse seismic imaging, micro-seismic monitoring, wellhead sampling with CO 2 tracers, down-hole logging, core sampling, surface gas monitoring, groundwater analysis, and satellite InSAR data. These methods have been instrumental in developing robust protocols for data collection and interpretation, offering critical insights into measuring, monitoring and verification (MMV) practices for CO₂ storage. Several tactics were employed: ○ Risk management and adaptation: A pre- injection risk register was established, guiding the development of the monitoring program. Regular quantitative risk assessments (QRAs) were conducted to update and refine risk management strategies. ○ Risk of migration: InSAR data and updated reservoir modelling identified potential risks of CO₂ migration beyond the intended storage area, leading to adjustments in injection strategies. ○ Well integrity: Issues with well integrity were addressed through increased monitoring and well maintenance. Measures included the suspension of CO₂ injection at certain wells and enhanced inspections. ○ Vertical leakage: Seismic data indicated potential vertical leakage pathways, prompting adjustments in CO₂ injection pressures and additional geo-mechanical studies. Tracer technology application Advanced tracer technology was employed to investigate CO₂ movement within a saline aquifer situated in the same stratigraphy as a producing field. Although various technologies were employed in the MMV process, tracers emerged as the most effective tool for distinguishing between natural and stored CO₂. enabled precise tracking of CO₂ sources and confirmed that CO₂ detected in production wells was not attributable to injection activities. Different CO₂ tracers were injected into each of the three CO₂ injection wells. The results revealed that CO₂ breakthrough was detected after approximately five years. This finding provided both source identification and proof of Results The use of RESMAN’s tracer technology

mass transport, which were not evident from seismic or other data. In this project, tracer technology achieved detection levels of parts per quadrillion (PPQ), providing remarkable resolution in the industry. Importantly, tracers are organic and safe, offering a high level of precision while maintaining a favourable safety and environmental profile. The In Salah project has yielded several critical lessons that can be applied to other CCS projects: ○ Thorough geological and geo-mechanical characterisation: Understanding the detailed geology and geo-mechanics of both the reservoir and the overburden is crucial. In Salah’s success underscores the importance of a comprehensive assessment of the subsurface environment. This includes evaluating rock properties, reservoir pressure, and the integrity of the cap rock to ensure the long-term stability of the CO₂ storage. ○ Regular and integrated risk assessments: The project highlights the need for ongoing risk assessments that integrate multiple data sources. By continuously evaluating data from various monitoring techniques, the project team can identify and mitigate potential risks early. This approach enhances the reliability of CO 2 storage and helps prevent unforeseen issues. ○ Flexibility in system design and operation: The experience from In Salah emphasises the importance of flexibility in the design and operation of CO₂ capture, compression, and injection systems. Adapting to new data and evolving conditions ensures that the infrastructure remains effective and efficient throughout the project’s life cycle. Implications for future CCS projects The In Salah project offers several implications for future CCS endeavours: ○ Enhanced monitoring techniques: The diverse portfolio of monitoring methods used in In Salah sets a benchmark for future projects. Implementing a similar range of techniques can improve the accuracy of CO₂ tracking and the overall safety of storage operations. ○ Comprehensive risk management: Future CCS projects can benefit from the rigorous risk assessment practices demonstrated at In Salah. Regular, integrated evaluations of geological, operational, and environmental data will help in managing and mitigating risks more effectively.