Considering the boost of hydrogen sector at large-scale, its underground sequestration is becoming increasingly important and represents a technological challenge at international level, being still little investigated. The objective of the study is to develop an experimental activity aimed at evaluating the interactions that occur between the fluid and the rock during the hydrogen geological storage process for safety purposes. In detail, we want to reproduce – on a small scale – what could be the situation of a typical Italian reservoir destined for the hydrogen storage.

For this purpose, the tests of interest have been defined. In detail the conditions (lithologies, temperature, pressure, duration of the test and type of fluid) to perform – in the laboratory – hydrogen injection tests (or possibly mixed with methane) have been defined. These tests carry out to investigate the behavior of the best caprock-reservoir system. The first step consisted in the recovery and preparation of the rock samples to be investigated. Three different lithologies have been identified: sand and rock salt for analyzes on reservoirs and clay for investigating caprock. Unlike the sand and rock salt which have been sampled, the procurement of clay has to be done.

Subsequently, in order to be able to characterize, from a structural and morphological point of view, the rocks and any changes that occurred following the injection tests, as well as to verify the possible formation of new mineralogical phases and to be able to perform a semi-quantitative analysis of the materials, XRD (X-Ray Diffraction analysis), SEM (Scanning Electron Microscope) and BET (Brunauer, Emmett and Teller) tests were performed on the undisturbed samples (i.e. before being subjected to the injection tests) of sand and rock salt. Even the clay sample – as soon as it becomes available – will be subjected to the same analyses.

In the continuation of the activities, all the samples will be subjected to hydrogen injection tests (or possibly mixed with methane) and the same analyzes will be performed again. The comparison of the results obtained upstream and downstream of the injection tests will allow to understand the processes and reactions that took place on the rock following the hydrogen injection and therefore to have an indication of the best caprock-reservoir system.

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