Very ambitious targets have been set for the decarbonisation of the energy system. These targets are mandatory at the global level and can only be achieved through the integration of energy carriers and systems, to be intended as flexibility tools to increase the use of non-programmable renewable sources. This gives rise to the need to implement systems for transforming electrical energy into other forms of energy and storing it in other energy carriers which can be used and reconverted with a view to increasing flexibility. While the injection of hydrogen directly into the gas network has already been tested in Italy, the geological storage technology for hydrogen (H2) is little known. In fact, although the upstream sector is one of the cornerstones and among most highly rated in the Italian industry, knowledge of the geological characteristics of oil & gas deposits in Italy is limited by data confidentiality constraints. Furthermore, the behaviour of the underground system with respect to the injection of fluids other than hydrocarbons or possibly carbon dioxide (CO2) is yet well known. Hydrogen has a very different phase diagram compared to traditional hydrocarbons and CO2, and these aspects must be carefully studied and verified. For the above reasons, therefore, a study aimed at evaluating the effects of underground storage of NG (natural gas) and H2 is essential, given that these mixtures, already injected into infrastructure linked to the gas grid, could be stored in deposits, to complete the grid storage capacity.

The overall activity aims to check, based on the chemical-physical characteristics of hydrogen, the possibility of storing hydrogen, pure or mixed with natural gas, inside deep deposits, through analytical estimates of the volumes and pressures involved. During the three-year research period, accurate hydrodynamic numerical analyses will be carried out with the available modelling suites will allow us to evaluate the feasibility of the industrial storage process and evaluate any hydrogen leaks along fractures and caprock.

The first part of the three-year period mostly focuses on an analytical survey of the different aspects of interest: position of the national system in the broader global and European context; chemical and physical features of hydrogen gas, for assessing the safety of its possible storage; a general overview of the various deposits already investigated for other purposes and for which a characterisation of the caprock-reservoir system is available, for describing their potential suitability to host hydrogen storage. Overall, this line of activity is aimed at the necessary alignment of national activities to the activities performed at the global/European level, with a view to an economy potentially based on the large scale use of hydrogen.