Stoccaggio geologico della CO2: analisi attraverso modelli geo-chimici

The purpose of the thesis is to investigate how injected CO2 might degrade the storage site from a geochemical point of view. Geochemical models play a pivotal role because they can identify the major mineralogical transformations induced by CO2. A series of simulations have been developed to analyse the reactive transport modelling, and possibly predict and quantify, the effects of the dissolution-precipitation processes driven by CO2 injection and the consequent changes in petrophysical properties (porosity and permeability) of the rocks. This thesis work follows an approach that, starting from the simplest cases, progressively moves towards to more complex scenarios. We started from the case of single cell or hot spot reactive models (0D models) to conclude with 1D reactive models. All the reactions driven by CO2 are taken in to account in the proposed models. The 0D models do not consider mass transport, but are useful for geochemical validation and for investigation of rock reactivity (thermodynamic and kinetic) by taking advantage of their low computational cost. The limitation of 0D models (neglecting mass migration) are exceeded with 1D models or dynamic models in which diffusion of primary species and migration of CO2 in the space can be simulated. All the numerical simulations were carried-out with e-muflot (Multiphase Flow and Transport), an Eni-internal software platform under development. This work could be deepened with future studies to arrive at the complete characterisation of the storage site by implementing 3D reservoir models. They will be useful in predicting more realistically the dynamics of CO2 plume migration in the storage complex and its effects on the lithology and petrophysical properties. This last step represents the ideal link/bridge between experimental activity and reservoir models.