Abstract:

Due to the small size and the large specific surface area of nanomaterials and the high atomic activity and high number ratio of the surface atoms thereof, various oil displacement functions can be integrated on the same nanomaterial through surface modification. Therefore, the nanomaterial oil-displacement technology is considered as one of the most potential EOR technologies in the future. The properties of nanomaterials for oil displacement are briefly introduced, and the research and application progress of zero-dimensional, one-dimensional and two-dimensional nanomaterials as oil displacement agents in oil fields are reviewed. Nano-silica modified by surfactants or polyacrylamide can reduce the interfacial tension between oil and water, change the wettability of rock, expand the sweep volume, and have other functions, showing good oil displacement effect. Owing to its stable property and economic and environmental protection advantages, silica is considered as the most promising zero-dimensional material for oil displacement. Metal oxide nanoparticles such as Al₂O₃, TiO₂ and ZrO₂, carbon nanoparticles and carbon quantum dots also have good oil displacement performance. One-dimensional carbon nanotubes can promote the migration and dispersion of surfactant molecules to the oil-water interface and improve the injection efficiency of oil displacement agents. Graphene-based nanofluids can significantly improve oil recovery by changing rock wettability and separation pressure, reducing interfacial tension, reducing oil viscosity, and controlling flow rate. Four challenges facing the application of nanomaterials in EOR are discussed, namely, the theory of nanomaterial flooding that needs to be broken through, the high manufacturing cost of nanomaterials, the dispersion stability of nanomaterials under reservoir conditions, and the separation and recycling of nanomaterials from produced fluids. Based on the demand of oilfield development and the current situation of nanotechnology development, the development direction of “composite function” and “intelligence” of the nanomaterial oil-displacement technology in oilfield in the future is proposed. “Composite function” refers to the integration of various functions on nanomaterials through chemical modification, such as stripping crude oil, trapping and merging oil droplets. “Intelligent” refers to the design and synthesis of flexible nanomaterials with adjustable bulk density at the oil-water interface by supramolecular chemical means, giving them the “intelligent” profile control function in the reservoir to achieve the purpose of expanding the sweep volume.

Key words: enhanced oil recovery, tertiary oil recovery, nanomaterial, oil displacement agent