The modelling of CO2 storage projects, especially with CO2 injection into regional aquifers, calls for an adaptation of the current modelling practices. This new modelling approach is especially mandatory with new simulation software, that enable directly coupled flow and poromechanical simulations, and which therefore use a single grid mesh to describe the geology. One of the aspects that comes into account is the representation of larger scales, both the temporal scale (representation of hundreds of years) and the spatial scale, with laterally the representation of the regional aquifer to model the expansion of the pressure front following the CO2 injection, and vertically the inclusion of burdens to represent geomechanical effects. To then run coupled simulations on a single support, this calls for the use of unstructured meshes that can first adapt to the representation of complex geological features such as faults, then conserve good computational accuracy [1], and finally vary laterally to decrease the number of cells and the computation time. This challenge is at the centre of the present paper. This work presents the use of adaptative hybrid meshes, composed of hexahedra, tetrahedra and pyramids, with a varying resolution. This type of mesh is used on a North Sea CO2 injection field model to perform fully-coupled flow/poromechanical simulations. The full workflow (grid construction, property filling, flow and poromechanical simulation) was successfully applied to build several models with different resolutions. The results of the simulations performed with these models were analysed looking at the extension of the CO2 plume as well as the mechanical impact of the CO2 injection. This analysis will illustrate the impact of the choice of lateral resolution, and will show that this innovative type of mesh enables this sensitivity analysis.