## 5 Methodology and Results
### Geomechanical Results  
Following an examination of the pressure impacts from CO\({}_{2}\) injection and the resultant CO\({}_{2}\) distribution within the reservoir, we now analyze the geomechanical responses. This part of the study addresses questions raised earlier, such as the practicality of using uplift measurements for monitoring purposes and the implications of subsidence patterns over the long term. We also look at how these ground movements relate to the position of the injection well and the dissipation of pressure during the post-injection phase. Additionally,  
Figure 8: CO\({}_{2}\) global molar fraction distribution at the end of injection and post-monitoring periods. The (**left**) illustrates the reservoir immediately after the 20-year injection phase and the (**right**) panel reveals the CO\({}_{2}\) distribution after 70 years. strategies for the strategic placement of monitors are considered, aiming to enhance the detection of vertical deformations. Figure 9 illustrates the temporal evolution of seabed uplift due to subsurface CO2 injection, captured at four different times: 3, 10, 20, and 70 years. The negative values shown correspond to an upward displacement against the downward-oriented \(Z\)-axis, reflecting rock expansion as a result of CO2 injection. Initially, significant uplift is observed, especially around the 20-year mark, indicating significant rock expansion due to CO2 injection and the reservoir pressure buildup. Over time, as the injection ceases and the system begins to equilibrate, the 70-year mark reveals a slightly decreased uplift at the reservoir's center. This change is attributed to the dissipation of pressure into the surrounding rock formations, which acts as a pressure-relief mechanism for the reservoir. The uplift is not uniform, with the largest displacement occurring slightly away from the wellhead, indicative of the CO2 migrating towards the flank of the reservoir where the structural conditions are conducive to upward movement. This suggests a more pronounced rock expansion in these shallower areas of the reservoir, with less overburden stress facilitating uplift. These insights challenge conventional expectations, particularly the intuitive anticipation of the largest displacements occurring at the wellhead location [36]. They emphasize the importance of a detailed understanding of temporal geomechanical changes for the design and monitoring of CO2 sequestration sites, highlighting the need for a comprehensive approach to address the implications of these changes on long-term storage integrity. The graph in Figure 10, showcasing vertical displacement at the wellhead (red) and the center of the reservoir (blue), provides a key insight into the geomechanical changes during and after CO2 storage. This phenomenon implies that the subsurface system is still dynamically adjusting to the introduced CO2 long after the injection phase has concluded. The data reveal a persistent ground movement due to pressure dissipation, extending beyond the injection period, which represents significant insight into the behavior of the storage system. It shows that the ground deformation rate is not null after the end of injection and that it can still be used as a source of data to be captured. Thus, their deployment can provide continuous monitoring of the geomechanical state of the CO2 storage site. Figure 9: Seabed uplift progression over time due to CO2 injection. Panels (**A–D**) show the seabed uplift at 3, 10, 20, and 70 years, respectively. The uplift is depicted as negative values of subsidence, signifying upward movement. Figure 11 illustrates the geomechanical behavior at the end of the 20-year injection period and brings a key insight related to the unexpected location of maximum uplift, which, as depicted in the vertical cross-section of the model, is not at the wellhead but rather closer to the center of the reservoir. This area, being shallower, is subject to less overburden stress, making it more responsive to the pressure changes induced by the injection process.