The effect of surfactant concentration, salinity, temperature, and pH on surfactant adsorption for chemical enhanced oil recovery: a review

Enhanced oil recovery (EOR) processes have a great potential to maximize oil recovery factor of the existing reservoirs, where a significant volume of the unrecovered oil after conventional methods is targeted. Application of chemical EOR techniques includes the process of injecting different types of chemicals into a reservoir to improve the overall sweep efficiency. Surfactant flooding is one of the chemical EOR used to reduce the oil-water interfacial tension and to mobilize residual oil toward producing wells. Throughout the process of surfactant flooding, selecting a suitable surfactant for the reservoir conditions is quite challenging. Surfactants tend to be the major factor associated with the cost of an EOR process, and losing surfactants leads to substantial economic losses. This process could encounter a significant loss of surfactant due to adsorption into the porous media. Surfactant concentration, salinity, temperature, and pH were found to be as the main factors that influence the surfactant adsorption on reservoir rocks. Most of the research has been conducted in low-temperature and low-salinity conditions. Only limited studies were conducted in high-temperature and high-salinity (HT/HS) conditions due to the challenging for implementation of surfactant flooding in these conditions. This paper, therefore, focuses on the reviews of the studies conducted on surfactant adsorption for different surfactant types on different reservoir rocks under different reservoir conditions, and the influence of surfactant concentration, salinity, temperature, and pH on surfactant adsorption.