INSAR ASSESSMENT OF THE UNDERGROUND GAS STORAGE-RELATED GROUND DEFORMATIONS: NEW OUTCOMES FROM A CROSS-CORRELATION APPROACH

Subsidence monitoring is an important task in urban areas where socio-economic and environmental considerations require careful assessment. The distinction between anthropogenic and natural phenomena is essential for precise monitoring and assessment of underground industrial activities, such as Underground Gas Storage (UGS). The present case study investigates InSAR monitoring of ground deformations induced by UGS activities above a gas field in Northern Italy operated by Snam and its subsidiary Stogit (the largest European UGS player with 60 years of experience in UGS management and monitoring). This region is characterized by long-term natural subsidence due to sediment compaction and anthropogenic subsidence (i.e., water withdrawal from shallow aquifers for domestic or industrial use). Ground movements were detected through high-precision InSAR measurements from 2015 to 2021, covering an area significantly larger than the field. Seasonal gas injection and withdrawal during UGS activities induce cyclical ground uplift and subsidence over time. A cross-correlation analysis was performed by comparing ground displacement time series with storage volume curves, aiming to identify the effective influence area of the UGS activities. The results showed that the peak of the UGS-related deformations remains inside the field area while the overall deformation gradually decreases towards the field boundary, becoming undetectable within a few hundred meters outside. This analysis contributes to a more precise definition of the storage activities' impact on ground deformations and delineates their areal extent on the surface, which is crucial for effective environmental monitoring and decision-making processes.