Unlocking the InSAR potential for managing underground gas storage in salt caverns

Abstract

Natural gas plays a key role in the ongoing transition to renewable energy, bridging the gap between conventional fossil fuels and cleaner alternatives. Despite the increasing emphasis on renewables, total reliance on electricity is still out of reach today, necessitating a transition period. The role of natural gas is particularly evident in addressing the challenges posed by seasonal fluctuations in consumption, a persistent issue for the global energy industry. In this context, Underground Gas Storage (UGS) facilities offer a flexible strategy to create global reserves and stabilise supply against demand fluctuations. Among the exploitable geological structures that are available for UGS, underground salt caverns allow high injection and withdrawal rates. However, these operations can induce subsidence due to cavern convergence and seasonal ground displacement resulting from operational cycles. This study employs multi-temporal Interferometric Synthetic Aperture Radar (InSAR) analysis, using Sentinel-1 data and the SqueeSAR algorithm, to monitor surface displacement at two UGS sites in Lower Saxony, Germany. The analysis revealed a vertical displacement velocity of up to 28 mm/year, forming a distinct cone-shaped deformation. Time series analysis showed a strong correlation between the injection/withdrawal cycles and the InSAR data. The threshold method identified UGS affected areas, offering a standardised framework for UGS monitoring. The study also introduced the RTK cross-correlation analysis to refine displacement interpretations, enhancing the ability to isolate gas storage induced deformation from unrelated surface processes. These results contribute for optimising injection and withdrawal strategies, mitigating subsidence risks and allowing the long-term sustainability of UGS operations. This approach can support robust management practices that prioritise safety and operational efficiency.

Keywords

• Underground Gas Storage
• Salt Caverns
• SqueeSAR
• Cross-Correlation Index
• Ground Displacement