Prediction of oil breakthrough time in modified salinity water flooding in carbonate cores

Abstract

Research carried out in the context of the modified salinity water flooding in carbonates showed that tuning the ionic composition of the injection water in core flooding experiments can lead to a more water-wet system, eventually affecting the flow of the oleic and aqueous phases. Previous endeavors for mathematically modelling this problem include complex reactive transport models and an indicator for the mobility alteration of phases. Thanks to a large number of fitting parameters, almost all proposed models can reasonably fit a limited set of core-flooding recovery data, which makes the choice of physical mechanisms for the development of a mechanistic model irrelevant.Here, we address this problem by correlating the geochemical interactions of potential determining ions with a two-phase transport model and performing a constrained history matching of the modified salinity water flooding tests in secondary and tertiary mode. Instead of matching only the recovery factor and pressure drop history, we give a higher priority to matching the different ion concentrations and oil breakthrough times. Our results show that the oil breakthrough times can only be correctly obtained by accurately modeling the carbonate-brine physicochemical interactions and choosing the adsorbed potential determining ions’ concentrations as a mobility-modifier indicator. The important observation is that for most core-flooding experiments, the lag between the start of the injection of the modified-salinity brine and the oil breakthrough time can be better predicted by considering the wettability alteration due to the adsorption of potential determining ions on the carbonate surface.