Interplay of interfacial tension and capillarity: Optimizing surfactant displacement efficiency in reservoirs

Document Type

Journal Article

Publication Title

Journal of Molecular Liquids






School of Engineering




King Abdullah University of Science & Technology / Resesarch Funding Office


Alaamri, J., Iglauer, S., & Hoteit, H. (2024). Interplay of interfacial tension and capillarity: Optimizing surfactant displacement efficiency in reservoirs. Journal of Molecular Liquids, 395, article 123915.


Surfactant treatments play a crucial role in formation cleaning and wettability alteration for reservoirs characterized by low porosity and permeability. One effective approach to enhance oil recovery in such formations is spontaneous imbibition (SI) driven by capillarity, which enables surfactants to infiltrate tight rock matrices. Through the reduction of oil/water interfacial tension (IFT), surfactants effectively diminish residual oil saturation, leading to improved oil recovery. However, excessive IFT reduction can hinder capillarity, resulting in inefficient surfactant penetration. On the other hand, forced imbibition (FI) does not rely on capillarity for surfactant penetration, and thus, improved recovery is primarily driven by IFT reduction. Consequently, achieving the optimal surfactant conditions necessitates a delicate equilibrium between IFT reduction and maintaining adequate capillarity to facilitate surfactant penetration. In this study, we explored the performance of three surfactant types (cationic, anionic, and zwitterionic) for oil recovery through SI and FI experiments, assessing their effects at both Darcy and pore scales. All tested surfactants successfully lowered IFT as anticipated but exhibited distinct impacts on wettability, as indicated by contact angle measurements. Consequently, the use of SI in Amott cell experiments did not yield favorable oil recovery improvements in Berea rock compared to the water baseline. Pore-scale assessments using Micro-CT revealed that the surfactants disrupted the connectivity of the oil phase within the rock, leading to reduced SI efficiency. In contrast, distinct recovery trends emerged with FI. To replicate the experimental results, we conducted pore-scale and Darcy-scale simulations, which serve as valuable tools for surfactant screening and optimization. This study underscores the importance of balancing IFT reduction and wettability alteration in surfactant screening to achieve optimized recovery efficiency based on the predominant recovery mechanisms.



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