Subsidence Analysis in the Italian Po Plain Area: An Extended Case Study

Summary The scope of the research is to cast light on the deformation characteristics of underground formations involved in gas storage (UGS) activities in the Italian Po Plain area. The reliable prediction of ground movement caused by reservoir compaction/expansion is mandatory for the safety of both storage systems and urban settlements (especially in high urbanized area) and it is dependent on a solid knowledge of the soil/rock deformation behaviour under changing stress. Two case studies were presented in terms of subsidence analysis via a multi-disciplinary (static/dynamic/mechanical) 3D numerical simulation approach. A coherent and full dataset is available for each reservoir modelling, which includes also deformation/strength parameters from lab and logs and 10+ years of InSar surface movement data adopted for the geomechanical model calibration. The cases show strong similarities in terms of structural/geological contest, formation lithologies and UGS strategies, among others. Based on the subsidence analysis results and the analysis of InSar data, a common correlation between induced pressure variation in each reservoir and corresponding ground movement was inferred, resulting in an equivalent deformation behaviour. The paper represents the first step in defining a common deformation response, if any, for the numerous UGS systems present in the Po Plain basin.