Acid‐based chemical slugs for enhanced oil recovery: Interfacial tension reduction, wettability alteration, and emulsion stabilization

Abstract The present study focuses on the development of acid‐based chemical slugs for enhanced oil recovery (EOR). These slugs interact with both the crude oil and the reservoir rock, resulting in favourable alterations to the reservoir properties. One of the key mechanisms involves a significant reduction in interfacial tension (IFT), which enhances oil mobilization and contributes to effective well stimulation. Notably, the interfacial tension between crude oil and the acidic solution decreases by more than 80% compared to that with water. This substantial IFT reduction is attributed to the acid's influence on the dissociation and behaviour of indigenous surfactants present in the crude oil. Additionally, acid‐based slugs improve reservoir permeability by dissolving clays and minerals within the rock matrix. The slugs also alter the wettability of oil‐wet rocks to water‐wet, with a more pronounced effect observed in carbonate rocks compared to sandstone due to mineral dissolution. Moreover, the formation of stable emulsions with higher viscosity than crude oil mitigates viscous fingering, reduces the mobility ratio, and enhances sweep efficiency. To address corrosion risks associated with acidic solutions, acid inhibitor is employed. Core flooding experiments demonstrate an approximate 12% increase in oil recovery over conventional water flooding, underscoring the potential of acid‐based slugs to improve displacement efficiency in EOR applications.