The shale caprocks of the saline aquifers, used for geosequestration, are highly heterogeneous and anisotropic due to their diverse mineralogical composition. The supercritical CO2 (ScCO2) adsorption on geomaterials constituting the caprock can be envisioned as the initial stage of many other chemical reactions that may happen over a larger time scale. In addition to trapping by adsorption, the volumetric expansion of the clay minerals due to intercalation of CO2 in their interlayer space can potentially seal off the existing fractures in caprocks and the fractures formed during the injection of CO2. The present study emphasises influence of the major minerals (clay and quartz) towards the adsorption of CO2 under the in-situ reservoir conditions of high pressure (15 MPa) and moderate temperature (35-55°C). Isotherm modelling was employed to estimate the adsorption mechanism and adsorption characteristics of the minerals. The variation of adsorption capacity and interaction potential of kaolinite, montmorillonite and their separate mixtures with quartz were estimated. ScCO2 adsorption on clay minerals were found to be multilayer physisorption with two layers of adsorbed phase. However, the influence of surface properties of the clay minerals towards adsorption was limited to the first layer of adsorption. The modelling results revealed the swelling of montmorillonite and kaolinite under suitable hydration state. The minimum pressure required to initiate swelling in clay minerals is found to be dependent on temperature as well as the clay-CO2 interaction potential. This pressure lies in the subcritical range for montmorillonite while for kaolinite, it reaches the supercritical range except for 55°C. Though, the addition of quartz was found to reduce the adsorption capacity of clay minerals, the swelling phenomenon persists in clay minerals irrespective of the quartz content.