A computer implemented method for determining a wettability alteration of a physical rock sample in the presence of at least two fluids, the method being characterised in comprising: performing a wettability alteration process to age a digital representation of the physical rock sample for a time interval, the performing comprising: setting up a rock sample simulation environment, comprising: retrieving , by a computing system, the digital representation of the physical rock sample and assigning input parameters and conditions for the wettability alteration process, wherein the digital representation of the physical rock sample, includes a digital representation of a pore space and a grain space corresponding to the physical rock sample; performing a drainage simulation to establish a fluid phase distribution for user-specified conditions comprising a reservoir pressure and temperature; calculating by the computing system, a local curvature for each surface location in the pore space; calculating , from the calculated local curvatures, a local capillary pressure and local disjoining pressure at each surface location in the pore space; determining , from the calculated local curvatures, whether water file breakage will occur at the surface, comprising comparing local capillary pressure to a sum of local curvature based pressure and local disjoining pressure; calculating a spatial distribution of wettability using a subset of surface locations eligible for water-film breakage and locations in contact with a non-wetting phase obtained after the drainage simulation; determining , for the subset of surface locations eligible for water-film breakage, a degree of wettability alteration based on local surface properties, local fluid chemical composition, and aging time; classifying, by the computer system, a wettability of the surface locations corresponding to the physical rock based on the determination of local curvature; and providing a numerical prediction of surface wettability alteration and a resulting spatial distribution of wettability in the form of a contact angle at each surface location. setting up a rock sample simulation environment, comprising: retrieving , by a computing system, the digital representation of the physical rock sample and assigning input parameters and conditions for the wettability alteration process, wherein the digital representation of the physical rock sample, includes a digital representation of a pore space and a grain space corresponding to the physical rock sample; performing a drainage simulation to establish a fluid phase distribution for user-specified conditions comprising a reservoir pressure and temperature; calculating by the computing system, a local curvature for each surface location in the pore space; calculating , from the calculated local curvatures, a local capillary pressure and local disjoining pressure at each surface location in the pore space; determining , from the calculated local curvatures, whether water file breakage will occur at the surface, comprising comparing local capillary pressure to a sum of local curvature based pressure and local disjoining pressure; calculating a spatial distribution of wettability using a subset of surface locations eligible for water-film breakage and locations in contact with a non-wetting phase obtained after the drainage simulation; determining , for the subset of surface locations eligible for water-film breakage, a degree of wettability alteration based on local surface properties, local fluid chemical composition, and aging time; classifying, by the computer system, a wettability of the surface locations corresponding to the physical rock based on the determination of local curvature; and providing a numerical prediction of surface wettability alteration and a resulting spatial distribution of wettability in the form of a contact angle at each surface location. <EOS>