Mechanisms of smart waterflooding in carbonate oil reservoirs - A review

The goal of the present paper is to provide a comprehensive review of the literature describing the physical and chemical mechanisms for enhanced oil recovery under smart waterflooding in carbonate reservoirs. Advanced, or smart waterflooding is a term denoting directed alteration of the ionic composition of the injected brine in order to achieve a better oil recovery, in particular, the low salinity flooding. While injection of a low salinity brine in sandstones is well described, the acting mechanisms of advanced waterflooding are not fully clarified, and only few reservoir-scale tests have been carried out. Demonstration and comparison of the different phenomena explaining the effect of smart waterflooding are the goals of the present review. Unlike the previous such reviews, we do not only concentrate on the phenomena occurring on the rock-brine-oil interfaces, but also address dynamic phenomena caused by flow, like fluid diversion and emulsification. The paper comprises an up-to-date information, classification and guidance and, consequently, is intended to serve advancing the research in the area of smart waterflooding in carbonates.