Carbon capture and storage (CCS) is expected to play a major role in societal attempts to reduce CO2 emissions and mitigate climate change. In parallel, CO2-based geothermal systems have been proposed as an innovative technology to couple CCS with geothermal energy extraction, therefore, increasing renewable energy production and unlocking industry-scale carbon capture, utilization, and storage (CCUS). The safe implementation and sustainability of both these technologies require a comprehensive understanding of how injected CO2 will interact with formation fluids and rocks in situ, especially under elevated pressure and temperature conditions. Whereas the role that CO2-bearing aqueous solutions play in geological reservoirs has been extensively studied, the chemical behavior of non-aqueous CO2-rich mixtures containing water has been vastly overlooked by academics and practitioners alike. In this study, we address this knowledge gap by conducting core-scale laboratory experiments that investigate the chemical reactivity of CO2-H2O mixtures, on both ends of the mutual solubility spectrum, towards reservoir and caprock lithologies. We conducted batch reactions on rock specimens from the Muschelkalk and Gipskeuper formations in Switzerland, subjecting them to interactions with wet CO2 under reservoir conditions (35 MPa, 150 °C) for approximately 500 hours. A wide range of high-resolution techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray computed tomography (XRCT), and stable isotope analysis, were employed to characterize the evolution of petrophysical properties, morphology, and chemical composition of the samples. Furthermore, upon experiment termination, we analyzed fluid effluents using inductively coupled plasma atomic emission spectroscopy (ICP-AES) to gain insights into ion transport processes associated with dissolution reactions caused by both the aqueous and non-aqueous phases. Our results reveal that fluid-mineral interactions involving CO extsubscript{2}-rich supercritical fluids containing water are significantly less severe than those caused by aqueous solutions containing CO extsubscript{2}. Nonetheless, the existence of dissolved ions in the wet CO2 samples is evidence of ion transport processes caused by the gaseous phase that warrants further investigation. The experimental characterization of CO2-H2O mixtures under a wide range of reservoir and operating conditions represents a critical step in ensuring the reliability, long-term security, and technical feasibility of deploying CCS and CO2-based geothermal energy worldwide.