The natural gas storage in underground structures known as geological reservoirs plays a key role in the Italian energy system. The gas storage satisfies various needs such as responding to the gas market demands, ensuring wide margins in the management of production facilities and transport nets and ensuring the maintenance of strategic reserves that are used exclusively to deal with exceptional situations.

Studies on natural gas storage are particularly interesting also for the analyses related to the seismicity. In fact, recent seismic events have emphasized the attention on safety aspects connected to industrial process related to the production and storage of natural gas. In these geological reservoirs, the fluid dynamics processes and the geological formation response are strongly interconnected. For this reasons, numerical modeling is very important because it is the only instrument that allows to carry out scenario analysis.

In this context, the present methodology has been developed to characterize gas storage sites and to simulate the related fluid dynamics behaviours as documented by a real scale – test case application focused to the Sergnano site located in Lombardia region (Italy). The methodology pointed out for the site characterization foresees the information collection about the stratigraphy and the lithology of the geological formations, the creation of a static geological model and then the realization of a corresponding 3D fluid dynamic model including the well cluster structures. In the shown case, the geological reservoir suitable for gas storage is located in the conglomerate formation known as Sergnano Gravel while the caprock is identified in the overlying clay formation known as Santerno Clay.

For this site, an accurate 3D numerical model, including geological and spatial discretisation, has been realized using GeoSIAM software system which allows to simulate the natural equilibrium steady state of the reservoir, to reproduce the industrial process, but also to evaluate the effect on the geological structure of the natural gas production and storage cycles. The obtained results have confirmed the goodness of the methodology based on the GeoSIAM system in terms of accuracy and reliability and its fundamental role to support sustainability analyses of gas geological storage.