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[References: 221 tit.]

Oil reservoir formation damage is a challenging issue associated with water and/or gas reservoir flooding in secondary and tertiary oil recovery operations. Some enhanced oil recovery (EOR) techniques offer the potential to overcome the multiple problems associated with formation damage and improve production rates and resource recovery. Regrettably, EOR techniques have their own problems to overcome, such as degradation of chemicals (polymers and surfactants) used under reservoir conditions, the large amount of chemicals required, and their high cost. Thus, the applications of nanotechnologies for oil-recovery enhancement offers huge potential benefits. Nanotechnologies can have positive impacts on the properties of subsurface porous media and the pore fluids present. They can assist in the separation of fluid phases, particularly oil and water, and introduce influential coatings to reservoir components. Moreover, nanomaterials can improve the performance of various sensors and control devices used as part of the production system. This study reviews NT laboratory- and field-scale tests to EOR and the ways in which NT can be applied to EOR to cause a reduction in capillary forces thereby enhancing oil displacement by reducing the wettability of the rock matrix and its interfacial tension.

It considers the potential of Janus nanoparticles (JNP) for certain EOR applications, contrasting the characteristics of JNP with nanoparticles (NP), and establishing that JNP tend to display higher stability. NP-enhanced carbon dioxide (CO2) reservoir flooding is of particular interest because of its capacity for carbon capture and storage (CCS). NPs act a stabilizer in nano-emulsions, CO2 nanofoams, and liquids containing surfactants and/or polymers. NP are also able to improve the quality of hydraulic fracturing, alter reservoir wettability, reduce interfacial tension, avoid formation damage and inhibit the precipitation of asphaltenes. This review describes the economic hurdles and potential environmental impacts confronting nano-EOR, and makes recommendations regarding future required research and likely EOR-related NP developments. The review's findings indicate substantial technical and commercial scope for expanded use of nanotechnology for EOR, in particular to enhance reservoir wettability and interfacial tension conditions.