A new model is presented, which considers the surface-complexation equilibrium between oil surface (amine and carboxylic groups) and rock surface (carbonate and calcite sites) with the brine solution. Effect of rock dissolution and oil composition on the number of available surface sites is taken into account. An in house finite volume solver, coupled with the geochemistry package PhreeqcRM, is utilized to model the multicomponent reactive flow of brine in chalk and the thermodynamic equilibrium between the oil and chalk surface. The equilibrium constants of the surface complexation reactions are tuned to the zeta potential measurements of chalk particles in different brines, and later adjusted to the chromatographic data for the flow of brine in the Stevns-Klint chalk cores. The effect of brine composition, temperature, and electrolyte models, i.e., (extended) Davies, Pitzer, and extended UNIQUAC on the solubility, and the results of the surface complexation model are studied and compared to a data set of the spontaneous imbibition experimental data for chalk. We found that the remaining oil saturation in the imbibition experiments is correlated with the number of bonds between the amine and carboxylate groups on the oil surface and the carbonate and protonated calcite on the chalk surface.@en