Ιn the context of rapid climate change and the urgent need for sustainable energy solutions, finding geological formations that can serve two purposes, supporting hydrocarbon production and enabling long-term CO₂ storage, is becoming increasingly important. This thesis explores the potential of diatomaceous formations to fulfill this dual role by performing a thorough geochemical and petrophysical analysis of selected diatomite samples.A multi-method approach was used, combining Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) for analyzing shape and elements, X-ray Diffraction (XRD) and Mineral Liberation Analysis (MLA) for identifying minerals, and BET surface area and Mercury Intrusion Capillary Pressure (MICP) tests for evaluating pore structure. Additionally, ICP-MS solubility tests and CO₂ exposure experiments were conducted to examine chemical reactivity and mineral stability.The samples mainly contained calcite, montmorillonite, and amorphous silica. They featured well-preserved diatom frustules, coccolithic structures, and calcium-rich cementation that added to their microstructural complexity. Short-term exposure to CO₂-rich water showed little change in SEM-EDS analysis, though ICP-MS data indicated limited cation release, suggesting subtle interactions between minerals and fluids.These results imply that diatomaceous formations may provide a promising capacity for enhanced oil recovery (EOR) and CO₂ geological storage. Further research, including core-flood experiments and fluid flow reactive transport modeling, is recommended to better replicate in situ conditions and evaluate long-term behavior of reservoirs.