The State-of-the-Art of wettability alteration in sandstones and Carbonates: A mechanistic review

Wettability modification plays a pivotal role in augmenting oil recovery from hydrocarbon reservoirs, rendering it a primary focal point during Enhanced Oil Recovery (EOR) procedures. By introducing external fluids into the oil deposit, the thermodynamic equilibrium of the oil-brine-rock system is changed, leading to reconfigured wettability. The term "wettability alteration" encompasses a wide spectrum of rock-fluid interactions that yield new wettability states, necessitating meticulous observations to comprehend the underlying mechanisms and devise effective injection fluids to attain desired outcomes. A comprehensive assessment of such interactions, with an emphasis on oil reservoirs, is absent, contributing to a limited grasp of the intricate processes governing wettability alteration in both sandstone and carbonate reservoirs. The present article delves into the funda-mentals of wettability and explores diverse mechanisms to alter the wetting characteristics of reservoir rocks.Herein, the fundamentals of wettability are first described, followed by an investigation into the potential mechanisms influencing oil wetness in reservoir rocks. The goal is to define the encountered problem and establish the basis for proposed solutions aimed at generating more water wet surfaces. In-depth analyses are conducted to examine wettability modification techniques, including low salinity water, surfactants, nanofluids, microbial, alkaline solutions, polymers, ionic liquids, and their combinations. Through a careful exploration of the chemical and physical bonds formed and ruptured between the surface and overlying fluids during the wettability alteration process, valuable insights are gained into the mechanisms governing wetting behavior. Furthermore, the most recent advances in wettability alteration by the abovementioned methods are tabulated in the article that compares the latest advancements and the factors that have been investigated by researchers, to shed light on the abundant methods of reservoir wettability enhancement.