Simulations carried out for low salinity water flooding often do not include geochemical processes. Salt concentration, and thus the salinity, is modelled as a water tracer that does not react with the reservoir formation. The goal of this MSc thesis is to improve the understanding of the influence of geochemical processes on the mixing of formation water and injection water, during low salinity water flooding. The geochemical processes taken into consideration are CO2-buffering, ion exchange and mineral dissolution. An initial understanding of the geochemical processes was gained by performing numerous simulations with the U.S. Geological Survey geochemical package PHREEQC. A limitation of this simulator is that it only allows for single-phase aqueous flow. To overcome this limitation, a multiphase Buckley-Leverett simulator has been developed in MATLABR that couples oil-water flow to the geochemical package PHREEQC. Subsequently, the newly developed simulator was used to study the effects of geochemical processes on the increase in oil recovery. In addition, simulations were performed to study low salinity slug sizes and dispersion. Although the low salinity mechanisms are still subject of extensive research, it is assumed that increases in oil recovery due to low salinity water flooding can be modelled as a change in relative permeability, from oil- or mixed-wet to more water-wet. Simulation results showed that fully removing calcite (calcite content 0.97 Wt%) from the reservoir, requires an excessive amount of pore volumes of low salinity water to be flushed through the reservoir. Therefore, dissolution of all calcite seems a near injector well-bore effect only. In the majority of the case study field, the minimum salinity level reached will be around 910 ppm. Simulations also showed that, during the injection of low salinity water into the case study field, Na+ attached to the cation exchanger is replaced by Ca2+. This is a result of the preferential adsorption of double valence ions when lowering the ionic strength, and decreasing the Na+/Ca2+ ratio in the reservoir. In simulation runs where geochemical interactions were included, higher salinity levels were observed in the reservoir compared to passive salt tracer simulations. In addition to an increase of 160 ppm due to the initial calcite dissolution, a secondary increase due to calcite dissolution as a result of cation exchange was noted. Depending on the amount of exchange sites, significantly higher ion concentrations (?2000 ppm) were observed. As the low salinity effect is assumed to be triggered solely by the salinity level, including geochemical interactions can therefore lead to a lower low salinity EOR potential. The increase in oil production observed for a non-geochemical affected secondary low salinity injection scheme (1.0 pore volume formation water followed by 4.0 pore volumes low salinity water) is 5.8% of the originally oil in place (OOIP) compared to a high salinity injection scheme (5.0 pore volumes of formation water), for low salinity thresholds ranging from 1000-3000 ppm. By including geochemical effects, the amount of incremental oil was 0.5%, 3.2%, 5.7% or 5.8% of the OOIP for a salinity threshold of 1000 ppm, 1500 ppm, 2000 ppm, or 3000 ppm, respectively. This indicates that, especially for low values of the low salinity threshold, geochemical interactions may be of importance for the EOR potential. However, it is important to note that the amount of calcite and number of cation exchange sites have been calculated based on bulk rock data. In addition, it has been assumed that the aqueous phase is in contact with all calcite and clay. By doing so, the effects of the geochemical interactions are overestimated. Dispersion was found to be very important for the determination of minimum low salinity slug sizes. However, no accurate dispersion data were available for the case study field to verify the current model. Simulation results showed that frequent (2 days/month) injection of seawater slugs during low salinity flooding may increase salinity levels throughout the whole reservoir above the threshold values, effectively eliminating the increase in oil production. Injecting larger seawater slugs on a less regular interval (2 weeks/year) results in fractions of the reservoir having a higher salinity than the threshold value. However, the overall impact on the cumulative oil production was far less (-0.6% of the OOIP compared to no seawater slugs). An interesting continuation of this project would lie in a detailed study of the chemical composition of the rock surface. As the cation exchange sites are likely to be less, the impact of cation exchange induced calcite dissolution on the salinity is reduced. This will result in an increase of low salinity EOR potential.