Modified salinity waterflooding in chalk reservoirs: A journey from rock and fluid interfaces to field scale applications

The positive effect of modified salinity water (MSW) injection on oil recovery has been broadly reported in the literature through core flooding experiment tests. Yet, the challenges in bridging the gap between laboratory to field scale studies still remain substantial, largely due to the lack of understanding of the underlying mechanisms involved. Also, it requires unraveling functional relationships and processes on each level. Injecting MSW into chalk reservoirs presents even more challenges due to the distinctive characteristics of chalk formations. Therefore, it necessitates a thorough comprehension of reservoir characteristics, rock-fluid–fluid interactions, and appropriate design strategies. In this work, we i) review the mechanisms controlling the MSW injection at the chalk surface, stemming from the interactions between the calcite, brine, and crude oil; ii) present the history matching of entire experiments conducted at core scale to obtain a salinity-induced shift in the relative mobility of the aqueous and oleic phases; and iii) address the current challenges in upscaling the observed benefit of MSW measured from core flood experiments to field-scale models for chalk reservoirs. Finally, we demonstrate how a set of relative permeability curves for different brines obtained from a large set of core flood experiments can be used to predict the performance of a Danish North Sea chalk reservoir.