Polymer flooding is one of the most promising techniques for the recovery of remaining oil from light oil reservoirs. Water soluble polymers are used to enhance the viscosity of displacing fluid and to improve the sweep efficiency. In this paper, water soluble polymers used for chemical enhanced oil recovery are reviewed. Conventional and novel modified polymers are discussed along with their limitations. The review covers thermal stability, rheology, and adsorption behavior of various polymer systems in sandstone and carbonate reservoirs. Field and laboratory core flooding data of several polymers are covered. The review describes the polymer systems that are successfully applied in low-temperature and low-salinity reservoirs. Comprehensive review of current research activities aiming at extending polymer flooding to high-temperature and high-salinity reservoirs is performed. The review has identified current and future challenges of polymer flooding.

Chemically enhanced oil recovery methods are utilized to increase the oil recovery by improving the mobility ratio, altering the wettability, and/or lowering the interfacial tension between water and oil. Surfactants and polymers have been used for this purpose for the last few decades. Recently, nanoparticles have attracted the attention due to their unique properties. A large number of nanoparticles have been investigated for enhanced oil recovery applications either alone or in combination with surfactants and/or polymers. This review discusses the various types of nanoparticles that have been utilized in enhanced oil recovery. The review highlights the impact of nanoparticles on wettability alteration, interfacial tension, and rheology. The review also covers the factors affecting the oil recovery using nanoparticles and current challenges in field implementation.