## 7 Conclusions  
The development and optimization of self-healing cement formulations incorporating Barite, Pozzolan, and Chalcedony have demonstrated their superior performance in CO2 injection and storage environments compared to conventional cement. By leveraging a Design of Experiment (DOE) approach, the study systematically identified the optimal compositions that enhance mechanical durability, self-sealing efficiency, and resistance to CO2-induced degradation. The porosity evolution analysis revealed that self-healing cement formulations exhibit rapid self-sealing within the first 7-14 days, significantly reducing crack formation and maintaining long-term structural integrity. The inclusion of Pozzolan and Chalcedony facilitated the formation of C-S-H gels, reinforcing the cement matrix and minimizing permeability. Additionally, Barite enhanced density control, thereby limiting fluid migration and improving resistance to mechanical failure in downhole conditions. Comparative analysis with conventional cement formulations (Figure 7) highlighted their progressive porosity increase, exceeding \(17\%\) over time, underscoring their vulnerability to CO2-rich reservoir fluids. The saturation index (SI) and phase volume changes further validated the stability of self-healing cement, demonstrating that key mineral phases such as ECSH2 and Calcite contribute to long-term strength and crack resistance. The results of this study provide a strong scientific foundation for the implementation of self-healing cement technology in CO2 sequestration, geothermal wells, and deep-sea drilling applications. By integrating optimized mineral additives, self-healing cement offers a cost-effective, durable, and environmentally sustainable solution to enhance wellbore integrity, mitigate fluid-induced degradation, and ensure prolonged operational reliability. These findings reinforce the potential of self-healing cement as a next-generation well-bore sealing material, capable of significantly reducing environmental risks and improving long-term well performance in extreme subsurface conditions. While the geochemical modeling results provide strong theoretical support for self-healing behavior, future work must include laboratory-scale validation under reservoir-relevant conditions. Specifically, experimental studies should evaluate crack sealing performance using split-cylinder or flow-through tests, measure permeability evolution during CO2 exposure, and quantify mechanical strength recovery after induced microcracking. Additionally, mineralogical analysis via XRD and SEM-EDS should be employed to verify the formation of C-S-H, Calcite, and other healing phases predicted by the model. These experiments will be essential to confirm the predictive accuracy of the PHREEQC simulations and support the practical deployment of the proposed formulations in CCS and geothermal applications. Looking ahead, the proposed self-healing cement system holds considerable promise for deployment in upcoming carbon capture and storage (CCS) fields, geothermal wells, and permanently abandoned wells that demand long-term zonal isolation. Its activation via CO\({}_{2}\) exposure aligns naturally with conditions found in CCS reservoirs, reducing the need for external triggers or complex activation mechanisms. Nevertheless, several field-scale challenges must be considered, including potential pumpability constraints due to solid additives, modifications to setting times, and variability in healing kinetics across heterogeneous reservoir environments. These challenges may be addressed through tailored slurry design, use of retarders and dispersants, and the integration of real-time monitoring tools such as fiber-optic or acoustic sensing systems to evaluate in situ healing performance. Pilot-scale testing and field demonstrations will be essential next steps to transition this technology from lab-scale validation to operational readiness under actual subsurface conditions. Conceptualization, A.A., K.S. and M.D.