A comprehensive review on surfactant-based enhanced oil recovery in clay-rich sandstone reservoirs

Clay-rich sandstones present significant challenges to enhanced oil recovery (EOR) due to the complex behavior of their abundant clay minerals, particularly during chemical flooding strategies. This study investigates how clay mineralogy, chemical interactions, and surfactant formulation collectively influence reservoir permeability, surfactant retention, and oil recovery efficiency. Through a critical review of recent literature, the research examines the mechanisms of clay swelling, fine particle migration, chemical adsorption, and the influence of environmental factors such as salinity and pH on surfactant-clay interactions. Experiments referenced include swelling, zeta potential, surfactant adsorption measurements, and core flooding trials under varying reservoir conditions. The results identify that montmorillonite and illite promote higher surfactant and chemical retention, exacerbating permeability loss. Specifically, surfactant retention can reach up to 0.22 mg/g of rock in high-clay-content cores, significantly increasing operational costs. While excessive surfactant adsorption by clays reduces EOR efficiency, appropriate surfactant selection and the synergistic use of low salinity or alkaline additives can mitigate detrimental effects. For instance, studies show improved oil recovery rates as high as 27.02% with optimized nonionic surfactants, and recovery factors up to 71.86% when integrating nanoparticles with surfactant systems. However, a persistent tradeoff exists between recovery gains and formation damage risks, which must be carefully balanced. Ultimately, the study underscores the necessity of matching surfactant systems and injection protocols to reservoir-specific clay mineralogy and salinity conditions. The findings provide a basis for optimizing EOR formulations to improve oil recovery in complex clay-bearing reservoirs. Meanwhile, future research should focus on developing advanced surfactants with minimal retention and exploring in situ monitoring to further reduce the impact of clays on oil production.