Carbonated Smart Water Injection (CSMWI) has a lot of interest, especially in the last decade. This interest stems from its results in the recovery factor enhancement and the permanent storage capacity of the carbon dioxide. This method has been mainly studied for sandstone formations, and less attention has been given in the carbonates and especially in the naturally fractured carbonates. In this thesis, the effect of the CSMWI on the recovery factor in the naturally fractured carbonates has been investigated. Furthermore, the capability of the CSMWI to store the CO2 permanently and safely in the reservoir has been studied. This work has been established based on core flooding experimental data, and it has been extended to a five spots model. CMG simulator has been used to generate the CSMWI model, and the sensitivity analysis tool has been used to identify the optimum water composition and salinity. To determine the CO2 molality and solubility in the obtained smart water, the PHREEQC simulator has been used, and the results have been introduced in the CMG model. Furthermore, the PHREEQC database has been used to define the geochemical reactions that could occur in the carbonates when the CSMWI is injected. CSMWI in the core scale showed more oil recovery than Smart Water Injection (SMWI), Carbonated Seawater injection (CSWI), and Seawater injection (SWI) by 14, 7.6, 26.8 %, respectively. In the pilot-scale model, CSMWI recovered more oil than the SMWI by 5 to 8% based on the heterogeneity and fractures availability. The mechanisms behind this increment are; mineral dissolution, ion exchange, viscosity reduction, and wettability alteration, which have been described and analyzed in this work. These mechanisms were studied in the fractures and matrices to illustrate the effect of the fractures on the oil recovery. More than 50% of the injected CO2 within the CSMWI has been permanently captured in the residual oil and water in the reservoir. It has been concluded that the stored CO2 in the reservoir depends on the amount of residual oil saturation. Where the higher the remaining oil in the reservoir, the higher the stored CO2 amount.