Impact of climate change on hydrogeomorphological dynamics: InSAR analysis of Underground Gas Storage and Carbon Capture and Storage

The contemporary climatic and political context has resulted in an increased reliance on natural gas as a transitional energy resource towards renewables, emphasising the essential need for efficient and sustainable Underground Gas Storage (UGS) operations. While UGS reservoirs are important for ensuring energy security and supply, their operations may impact the surface and subsurface environments, raising concerns about induced seismicity, subsidence and environmental risks. This PhD Thesis explores the potential of InSAR (Interferometric Synthetic Aperture Radar) technology as a robust tool for monitoring UGS sites, focusing on its applications for detecting surface deformation and assessing environmental impacts. The research encompasses the analysis of multiple case studies, representing a variety of geological contexts, reservoir types, depths and environmental settings. The PhD Thesis demonstrates the versatility and effectiveness of InSAR in providing high-resolution, temporally continuous data on surface displacement. The selected UGS case studies include both porous reservoirs, such as depleted fields and aquifers, and salt caverns. The comparison of these cases reveals the varying displacement patterns associated with different types of UGS reservoirs, including seasonal cycles of uplift and subsidence in porous reservoirs and more complex, gradual subsidence in salt caverns. The methodological framework adopted integrates fundamental analyses, such as the time series analysis of ground displacement trends, with operational injection/withdrawal cycles, through sophisticated techniques of cross-correlation analyses. The proposed procedure facilitates a more nuanced understanding of the relationships between the detected surface displacement and the underlying geomechanical reservoir processes. Moreover, the use of freely accessible and open-source InSAR datasets, notably the European Ground Motion Service (EGMS), serves to emphasise the affordability and accessibility of remote sensing technologies for the purpose of gas storage monitoring. The research culminates in the formulation of best practices for InSAR-based UGS monitoring, addressing the current gaps in the literature and proposing a standardised methodology for global application. The best practices emphasise the importance of a multidisciplinary approach that integrates InSAR data with other monitoring technologies, including well log data, fibre-optic, seismic and micro-seismic data, and temperature and pressure monitoring, to achieve a comprehensive understanding of UGS-related dynamics. This PhD Thesis also examines the environmental implications of underground storage in the context of Carbon Capture and Storage (CCS) operations. Utilising InSAR technology for remote sensing monitoring, the research highlights a proactive approach for managing environmental impacts, particularly in ensuring carbon dioxide (CO₂) containment. Achieving effective CCS operations is imperative for mitigating greenhouse gas emissions and achieving the climate targets outlined by the International Panel on Climate Change (IPCC). The integration of InSAR into CCS monitoring frameworks is identified as a promising avenue to support the scalable deployment of CCS projects, emphasising its role as a reliable and environmentally sustainable tool. The PhD Thesis makes a significant contribution to the field of gas storage monitoring by demonstrating the potential of InSAR technology in addressing environmental, operational and regulatory challenges. By analysing key reservoir characteristics such as capacity, depth and geological composition, this research identifies typical deformation patterns associated with gas storage operations, providing a new framework for interpreting surface displacement data. The insights gained lay the groundwork for developing standardised monitoring protocols, ensuring safer, more efficient and environmentally sustainable management of gas storage reservoirs.