Low-salinity flooding (LSF) is an improved-oil-recovery method that consists of injecting brine with lower salinity than conventional formation water into the reservoir rock. This method has the potential to improve the oil recovery beyond conventional waterflooding. In sandstone reservoir rocks, it has been reported that the salinity range should be below 5000ppm, whereas for carbonate rocks, laboratory experiments have shown that seawater, which has salinity generally neighboring 50000 ppm caused low-salinity effect. In order words, there was higher oil recovery in secondary mode and additional oil recovery in tertiary mode. Likewise, brines with even lower salinity (highly diluted seawater), trigger incremental oil recovery in the range of 5-10% or even higher. In some other cases, no incremental oil recovery had been observed at all. Consequently, the bandwidth of views ranges from doubt that the low salinity effect for carbonates exists to the potential of relatively high incremental oil recovery. Therefore, the main challenge remains to figure out the true existence of the LSF effect in carbonates, and the understanding of the underlying mechanisms, which ultimately represents a risk in a potential full field scale LSF in carbonates technology deployment. In this project, a similar experimental approach (model system experiments) as in the previous study (Mahani et al., 2014) was taken. The carbonate rock surface is created with patches made of carbonate suspensions (e.g. dolomite, limestone or chalk), deposited on a microscope glass substrate. In addition, oil drops are deposited on the patches and the samples are exposed to brines for investigation at ambient temperature. A camera takes pictures continuously at regular interval of time, from which, contact angle measurement is done, indicating the response of oil drops. This type of experiment was coupled with surface chemistry studies of the system crude oil/brine/ carbonate rock. The results show that surface charges at the rock/brine interface and oil/brine interface tend to be more negative as brine salinity decreases, which translate to lower zeta potential. In addition, the behavior of zeta potential as a function of pH depends on brine composition. Finally, these surface charges at the rock and oil surface are likely to be the main mechanism for the low salinity effect in carbonates, by inducing electrostatic repulsion. In fact, we were able to determine a cause-and-effect relationship between wettability change in different low salinity brines and the zeta potential values. Nevertheless, mineral dissolution could act as a secondary mechanism, by enhancing wettability change through the release of Ca/Mg from the carbonate rock surface, which breaks the bond between the oil-polar groups and the carbonate surface.