Role of rock material on low salinity waterflooding investigations in chalk reservoirs

Low salinity water-flooding is an EOR method that potentially modifies the equilibrium of the initial crude oil/brine/rock system to a condition that is favorable for additional oil to be mobilized in the porous media. The uncertainties associated with this EOR method are greater when dealing with a real crude oil and a highly reactive rock material. Chalk reservoirs are particularly challenging because of their low matrix permeability, high porosity, high degree of heterogeneity, and high tendency for surface reactions. In the literature, experiments on outcrop chalk cores have been extensively reported, however, there is still a lack of data for reservoir chalk material, and further, there are no results on preserved core materials showing how differently they might behave compared to dry-stored reservoir plugs. There is thus a question of how the wetting condition of the reservoir is represented by these types of samples. Therefore, besides investigating the role of brine salinity on wettability alteration and oil recovery factor, this work aims to evaluate the effect of using different core materials through a series of systematic contact angle measurements and core-flooding experiments on Stevns Klint outcrop samples, cleaned and dry-stored reservoir core plugs and preserved reservoir materials.