The synergistic effects of nanoparticle-surfactant nanofluids in EOR applications

Enhanced oil recovery (EOR) techniques are receiving substantial attention worldwide due to the major decline in the available oil resources. However, lots of challenges and limitations such as high costs, low sweep efficiency, and possible formation damage hinder the improvement of these EOR techniques. In addition, nanoparticles have proven to be potential solutions or improvements to a number of challenges associated with the traditional EOR techniques. Furthermore, surfactants are added to nanoparticle solutions to enhance their stability. In general, surfactant-coated nanoparticles are functionalized nanoparticles that consist of a nanoscale part with their surface active groups to perform specific tasks such as adsorbing at the oil-water interface to modify some of their properties including wettability and interfacial tension (IFT). The relative concentration ratio between surfactants and nanoparticles defines the properties of the modified surfactant-coated nanoparticles. If the concentration ratio between surfactants and nanoparticles is low, only a small portion of the nanoparticles would be coated with surfactants. Conversely, large concentration ratios mean that surfactants can form a double layer on the particle's surface. The interactions between surfactants and nanoparticles can lead to a considerable change in the surface activity of surfactants. Multiple layers of surfactant-nanoparticle can be formed by the strong attraction between surfactant and nanoparticle molecules. Generally, surfactants with higher concentrations, which are entitled with a higher adsorption into the surface, can greatly reduce the interfacial tension (IFT) and alter the wettability towards a water-wet condition. The aim of this paper is to conduct a review of the recent literature on nano-technology and determine the most reliable mechanisms associated with different particles. The paper mainly focuses on the development and usage of nanoparticles in combination with surfactants to improve and enhance oil recovery. Different tests and experimental studies are presented to better understand the recovery mechanisms of the combination. The first part of this paper focuses on the recovery mechanisms of different types of nanoparticles. Next, the recovery mechanisms of surfactant-nanoparticle solutions are presented along with different experimental studies. Finally, the possible limitations and challenges that face the combination of surfactants and nanoparticles in EOR applications are presented.