LAUSR

Abstract Low salinity/Smart water injection (LSWI) is a promising enhanced oil recovery (EOR) method, where manipulating the injected water compositions helps in recovery from oil reservoirs via alteration of the rock wettability towards a more water-wet state. The geochemical interactions involved in this process are crucial in determining the wetting state and therefore, should be considered in evaluating the effect of injection waters with different compositions. In this paper, the experimental data of LSWI in a carbonate core sample have been simulated and matched. The experimental results of oil recovery by injection of four different waters were examined, and the relative permeability curves were adjusted using a dynamic wettability alteration approach. Moreover, results of drainage and imbibition tests used to approximate the corresponding capillary pressures. True effective mobility (TEM) functions were also derived to evaluate the two-phase flow characteristics of the systems. Relative permeability and capillary pressure parameters showed strong correspondence with the injected salinity, and correlations were proposed for estimating the unknown parameters in other similar studies with different salinities. The trend of wettability alteration by LSWI was investigated, and it was concluded that the wettability does not linearly change with salinity, but rather it is non-linearly correlated with the logarithm of the total injected salinity. Injection of seawater (SW) did not significantly change the wettability and flow efficiency of the system compared to formation water (FW). However, dilution of SW to the salinity of 5000 ppm seemed to be the critical threshold below which the effect of LSWI had become substantially more pronounced. The results of this study can be helpful in optimizing and upscaling similar smart water applications, predicting the wettability-related parameters and two-phase flow characteristics at different injected salinities, and also block-to-block modelling in which the effect of the capillary pressure in the fracture network is also considered. Additionally, the non-linear relationship of the wettability-related parameters with salinity is particularly considerable for modifying the common modelling approaches of wettability alteration by LSWI in commercial simulators.