Impact of SO₄²⁻, Ca²⁺, and Mg²⁺ ions in Caspian Sea ion-engineered water on the rate of wettability alteration in carbonates,

Abstract

Tuning salinity and concentrations of potential determining ions (Mg²⁺, Ca²⁺, SO₄²⁻) in Caspian Sea water can substantially speed up wettability alteration in carbonate rocks via the multi-ion exchange (MIE) mechanism. At 15 000 ppm salinity, Caspian Sea water changes contact angle from 86° to 35° in 2 days. A five-fold dilution achieves the same in 9 hours, and spiking Ca²⁺ and SO₄²⁻ further reduces the angle to 22° in 9 hours. Spontaneous imbibition tests show that oil production rates double with ion-engineered brine. Optimizing such brine compositions could make engineered water flooding in carbonate reservoirs more efficient and economically attractive.,