Preliminary investigation on the geological potential for underground hydrogen storage (uhs) in saline formations in italy

In the last years, energy transition from fossil fuels to renewable resources has been largely acknowledged as a necessity to reduce emissions of greenhouse gases in the atmosphere. Hydrogen, the simplest element on Earth, can play an important role in this transition. It is not as an energy source but rather as an energy carrier: in layman’s terms, electricity is converted in chemical energy, which can then be converted again in electricity or in green methane, if combined with carbon dioxide. Because hydrogen can be obtained from the excess of electricity produced from power plants or from renewable energy sources, such as solar panels or wind mills, it is a clean and sustainable form of energy, to be stored and used when needed. As a consequence, a key issue is hydrogen storage. Large metallic containers are typically used to this end but their capacity is limited. Given the increasing hydrogen production and perspective large use, the only viable alternative is underground storage in geological formations, which can be depleted hydrocarbon reservoirs, deep saline aquifers, or cavities in salt domes. Underground hydrogen storage (UHS) is already in use in various countries and mostly in salt caverns artificially made by circulation of fresh water. In the Italian territory there are several areas where saline deposits are both observable as outcrops or detected deep in the subsoil. Their thickness and their geological, petrophysical and mechanical characteristics vary from one area to another depending on the depositional conditions, which favored the formation of different sedimentary facies. These characteristics have a strong impact on the decision to convert a saline dome into a hydrogen storage and, therefore, they should be thoroughly investigated. The aim of this work is to map the salt formations mapped on the Italian territory and to preliminarily assess their potential on the basis of the geological characteristics for a possible future use as underground hydrogen storages.