###### Abstract  
Geological Carbon Storage (GCS) involves storing CO\({}_{2}\) emissions in geological formations, where safe containment is challenged by structural and stratigraphic trapping and caprock integrity. This study investigates flow and geomechanical responses to CO\({}_{2}\) injection based on a Brazilian offshore reservoir model, highlighting the critical interplay between rock properties, injection rates, pressure changes, and ground displacements. The findings indicate centimeter-scale ground uplift and question the conventional selection of the wellhead as a monitoring site, as it might not be optimal due to the reservoir's complexity and the nature of the injection process. This study addresses the importance of comprehensive sensitivity analyses on geomechanical properties and injection rates for advancing GCS by improving monitoring strategies and risk management. Furthermore, this study explores the geomechanical effects of modeling flow in the caprock, highlighting the role of pressure dissipation within the caprock. These insights are vital for advancing the design of monitoring strategies, enhancing the predictive accuracy of models, and effectively managing geomechanical risks, thus ensuring the success of GCS initiatives. GCS; geomechanics; caprock; ground deformation monitoring; saline aquifer 2024202414069. 2024202414069.  
is proof of safe and reliable storage. For that, CO\({}_{2}\) can take advantage of different trapping mechanisms in porous media [2; 3; 4; 5]; for example, free CO\({}_{2}\) migration is controlled by the structural and stratigraphic trapping exerted by the caprock during the short term, encompassing the injection time, known as a primary mechanism. During this stage, the caprock plays an essential role in the security of the geological storage operation due to CO\({}_{2}\)'s buoyancy, which can move it up to the surface in onshore fields or the seafloor in the case of offshore storage sites. In the Frio CO\({}_{2}\) field demonstration project conducted in the U.S. [6], CO\({}_{2}\) was injected in a deeper zone below several well-known shale seals. However, some authors [7] are currently reviewing the need for a caprock to control the plume rising because (i) there is no prescriptive regulation concerning geologic seals and (ii) a composite confining system, e.g., a set of discontinuous barriers, can create long and tortuous paths that attenuate the mobile CO\({}_{2}\) saturation. During the mid and long term, part of that mobile CO\({}_{2}\) will be dissolved in water (solubility trapping) as time passes, especially in low-salinity brine under high-pressure and low-temperature conditions [8; 9]. Molecular diffusion and brine solubility are the main physical phenomena that facilitate the dissolution of CO\({}_{2}\) into a brine. As CO\({}_{2}\) dissolves into saline water, the density of the resulting CO\({}_{2}\)-dissolved brine increases. This density difference between the CO\({}_{2}\)-dissolved brine and pure brine leads to the sinking of the denser CO\({}_{2}\)-dissolved brine, while the pure brine rises [10; 11]. Density-driven convective mixing accelerates the rate of mass transfer of CO\({}_{2}\), promotes its dissolution, and enhances the stability and safety of the geological storage [12; 13; 14]. In addition to the solubility trapping, saturation changes caused by the rising plume can lead to more CO\({}_{2}\) being trapped as a residual phase due to relative permeability and capillary hysteresis [15; 16; 17]. On saline aquifers, thermally enhanced dissolution of the CO\({}_{2}\) occurs [18]. Beyond that, in a few cases, some CO\({}_{2}\) can be trapped as minerals because of the resulting pH of the brine and the mineralogy of the rock [19; 20]. Therefore, those additional mechanisms increase storage security when the buoyant CO\({}_{2}\) is immobile in the pore space or no longer exists as a free phase (generally, as supercritical CO\({}_{2}\)).