In this study, the first set of experiments were done to investigate the impact of low salinity water flooding on limestone core plugs. In this section, the effluents from core flooding experiments has been analysed to find out the related mechanism while enhancing in oil recovery (EOR) was observed. Reduction in Ca 2+ and increment in Mg 2+ ion in the effluent showed ioin exchange during EOR. The Mg 2+ ion content in the effluent may caused by mixing the injection brine with connate water, as well as detaching the ion from dolomite in the rock. Rock dissolution as a mechanism was observed during injection of low salinity brine (salinity 3000 ppm). In the second part of experiments, the effect of bicarbonate as the determining potential ion has been investigated. Oil and brine contact test has been done as well. Core flooding experiments have been conducted on homogeneous and heterogeneous core plugs. Inceasing the pressure drop across the homogeneous core plug showed permeability reduction. The same scenario has been done on heterogeneous core plug and increase in oil recovery was observed. Fines migration and emulsification which was followed by flow diversion to un-flooded zones were among introduced mechanisms. The related analyses to see the interactions between oil, brine and rock sample has been done in this session. Also the emulsion structure was observed under Cryo-SEM microscope. The droplet size was in the bigger size around 300 micrometer. This size is enormeously higher than the carbonate core pore size which approve flow diversion using fractured core plug. The interfacial tension between different concentration of bicarbonate solutions and North sea crude oil were conducted as well. The measurements were conducted at 200 bar and different temperatures. Temperature showed positive effect on IFT reduction of bicarbonate solutions. While for formation water, seawater and deinonized water, 60 °C was the threshold, until that IFT was reduced and any more increase in temperature resulted in higher IFT. Using Scale-CERE softeware and calculating the amount of CO 2 , higher salinity and temperature, showed releasing more carbondioxide. In a part of the study, predicting relative permeability and capillary pressure curves were achived. LET and Skjaeveland correlations were used and the parameters were achived by introducing objective function. The parameters of correlations were corrected by matching oil recovery and pressure drop data from first set of core flooding experiments.