The mechanism of wettability alteration through water injection, temperature effect (a) Rock is negatively charged in SW, 10SW, SW-4S, and 10SW-4S brines (ζ ₁) and also the charge at the oil/water interface is negative (ζ ₂). Increasing temperature causes more negative surface charges at the both oil/brine interface () and rock/brine interface (), therefore more electrostatic repulsion exists when temperature increases and wettability shifts into more water-wet states. (b) Rock is positively charged in SW-4Ca (ζ ₁) and also the charge at the oil/water interface is negative (ζ ₂). Increasing temperature causes more negative surface charges at the oil/brine interface () and more positive surface charge at the rock/brine interface (), therefore more electrostatic attraction exists when temperature increases and wettability shifts into more oil-wet states.