GROUND DEFORMATION MONITORING ABOVE UNDERGROUND GAS STORAGE FIELDS: EVIDENCES AND NEW INSIGHTS FROM InSAR AND GNSS

This study investigates the relationship between Underground Gas Storage (UGS) operations and ground deformation using Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS) data. InSAR and GNSS data acquired over UGS fields reveal distinctive patterns in the vertical ground deformations linked to subsurface storage activities, enabling the identification of the UGS influence area. As UGS operations involve seasonal gas injection and withdrawal that induce seasonal uplift and subsidence, the seasonal amplitude [mm] of ground displacement is the most appropriate parameter for describing the surface effects of UGS. The research focuses on the analysis of the UGS effects for depleted reservoirs hosted within clastic deposits in anticline structural traps, with over 40 years of underground storage activity. InSAR data were analyzed to quantify seasonal uplift and subsidence patterns associated with the UGS operational cycles, along with the cross-correlation parameters R and K, which quantify the degree of correlation between ground movements and gas storage activities. The 2D maps of InSAR-derived vertical seasonal amplitude typically exhibit a peak of displacement above the UGS field, where the seasonal oscillations reach their maximum and decrease radially in all directions (e.g., Teatini et al., 2011; Codegone et al., 2016; Benetatos et al., 2020; Wang et al., 2022). The InSAR measurement points located directly above the UGS field display a strong correlation with the UGS activity. On the contrary, the InSAR measurement points located farther away exhibit almost null UGS-related impacts. The available GNSS measurements provide InSAR-complementary results. GNSS data are consistent with the station site position relative to the InSAR amplitude peak, and help in constraining the spatial extent of the effective influence area of the storage activity (e.g., Benetatos et al., 2020; Codegone et al., 2024). The analysis underscores the potential role of the structural trap geometry and bounding fault in influencing surface subsidence and uplift deformation patterns. These findings emphasize the importance of a detailed monitoring using advanced technologies, along with a comprehensive understanding of subsurface geology, to effectively manage UGS operations, particularly as the global demand for gas storage continues to rise worldwide.