We develop a model that takes into account the combined effect of transport and chemical reactions for the study of various flooding experiments with chalk cores where the flooding involves seawater-like brines. The chemical system we consider is based on a selection of the most prominent ions and minerals relevant for the lab experiments in question. We include mechanisms such as advection, diffusion, and water-rock chemistry in terms of precipitation and dissolution, ion exchange, aqueous equilibrium of carbon species, complexes, and charge balance. The aqueous chemistry and the ion exchange processes are assumed to take place instantaneously whereas kinetic is included for the dissolution/precipitation processes. An important motivation behind the development of the model is to bring forth a model that can support the study of water-weakening effects as well as brine-dependent oil recovery in the context of chalk reservoirs. In particular, we test the performance of the proposed model by comparing with some recent flooding experiments involving MgCl2 type of brines and seawater-like brines. The measured effluent concentrations reflect that there typically are some rapid transient effects for small times followed by some slower transients, and finally, convergence to steady state concentrations. For a fixed set of reaction rate constants, various standard thermodynamic constants, flow injection rate, and diffusion coefficient, the proposed model is able to capture main trends of the measured outlet ion concentrations for a set of tests with the above mentioned brines. Consequently, the model shows that the experimental behavior can possibly be understood as a result of an interplay between advection and diffusion, and water-rock interaction in terms of precipitation/dissolution of minerals and ion exchange processes. We use the model to detect the role played by the different components, in particular, the role played by the ion exchange and the dissolution/precipitation which seems important for further investigations of brine-dependent water weakening and oil-recovery mechanisms. (C) 2012 Elsevier Ltd. All rights reserved.