Smart Water injection to enhance oil recovery in carbonate reservoirs – Acid number and base number adsorption onto chalk

Abstract

Water-Based Enhanced Oil recovery (EOR) by injecting "Smart Water" in Carbonate Reservoirs have shown promising results. The success of EOR-process waterflooding by “Smart Water” is dictated by the initial wetting condition of the rock and the potential of EOR methods related to wettability alteration. It is also found that adsorption of polar organic components has the largest effect on the wettability alteration in carbonates. The main objective of this paper is to show adsorption of polar organic components towards water wet chalks surface with different initial water saturation (0%, 10%, and 100%). Three cores with 0%, 10%, and 100% initial water saturation were flooded 15 pore volumes (PV) of crude oil with fix Acid Number (AN=0.35 mgKOH/g) and Base Number (BN=0.20 mgKOH/g) at 50° C. The core without initial water saturation adsorbed most polar components in comparison with other cores. Wettability of the cores was analyzed by spontaneous, forced imbibition and chromatographic wettability tests. Based on oil recovery and chromatographic wetting index, the experimental results showed that the core initially saturated with 100% water behaved more water-wet core than other two cores. The observations were in the followings: 1) The wetting condition of chalks is strongly linked to the acidic oil components. 2) As adsorption of polar components on the rock surface increases, it continuously causes decrease of water wetness.3) Initial water saturation has a strong influence on the wetting condition, as increasing water saturation can be seen to provide a more water wet condition because of reducing the amount of appropriate cites for adsorption in the core.