## 6 Results and Discussion
### Phase Volume Changes and Mineral Transformations
Additionally, Barite enhances the density of the cement matrix, limiting CO\({}_{2}\) penetration and improving mechanical stability, thereby reducing the risk of structural failure. In contrast, the conventional cement (teal curve in Figure 7) fails to maintain porosity stability, exhibiting a continuous increase in porosity exceeding 17% over time. This trend indicates progressive degradation, primarily due to the dissolution of Portlandite and C-S-H phases under CO\({}_{2}\)-rich conditions. As these critical cementitious phases deteriorate, the cement structure weakens, accelerating permeability loss and increasing the risk of CO\({}_{2}\) leakage. Unlike the self-healing formulations, conventional cement lacks reactive mineral phases such as Pozzolan and Zeolite that enable self-sealing behavior, making it highly vulnerable to CO\({}_{2}\)-induced failure. The comparative analysis between advanced self-healing cement and conventional cement underscores the importance of mineral optimization in enhancing cement durability in CO\({}_{2}\)-rich environments. The integration of Pozzolan and Zeolite not only improves early-stage self-sealing but also ensures long-term resistance against CO\({}_{2}\)-induced dissolution and structural weakening. In comparison with previous research on conventional and alternative self-healing cement systems, the proposed formulation demonstrates several notable advantages. Traditional Portland cement, while widely used, is known to degrade rapidly under CO\({}_{2}\)-rich conditions due to the dissolution of Portlandite and C-S-H phases, leading to increased porosity and loss of mechanical strength [9; 42]. Prior strategies to enhance cement durability have included polymer-modified cement [43; 44], elastomer-based systems [13; 45], and microcapsule-reinforced cement [32; 49]. However, these approaches often face challenges related to thermal stability, mechanical robustness, or cost-effective scalability. For example, polymer-enhanced systems may exhibit reduced compressive strength or premature healing agent release under high-temperature conditions, limiting their effectiveness in geothermal and CCS wells. In contrast, the cement formulation developed in this study utilizes thermochemically stable mineral additives--Barite, Pozzolan, and Chalcedony--that react in the presence of CO\({}_{2}\), a naturally available trigger in the targeted reservoir environments. This ensures reliable activation without the need for external fluid infiltration or microbial activity. The observed porosity reduction and consistent phase stability demonstrate the superior self-sealing and durability of the proposed formulation under harsh subsurface conditions. Figure 3 further contextualizes these findings by comparing the healing capability of various self-healing materials across published studies. As illustrated, most materials are limited to healing crack widths significantly smaller than the 500 \(\upmu\)m threshold commonly reported in oil and gas applications [52]. Only bacterial-based self-healing systems have demonstrated the ability to seal such large cracks; however, these systems face limitations under actual reservoir conditions. Specifically, microbial self-healing mechanisms may be compromised in CO\({}_{2}\) injection environments due to high pressure, low pH, elevated temperature, and shear forces, which challenge bacterial viability and metabolic activity [48; 51; 52]. This highlights a critical gap in current self-healing technologies: while several laboratory-scale materials demonstrate promise, few are engineered to withstand the coupled mechanical-chemical stresses encountered in CCS or geothermal wells. The cement formulations proposed in this study offer an inorganic, thermochemically robust alternative that operates independently of biological or fluid-activated triggers and show early signs of scalability and adaptability under harsh CO2 reservoir conditions. Despite these promising results, it is important to recognize the limitations of this work.