YE Hang^1,2, LIU Qi^1,2, PENG Bo^1,2, LUO Dan³

1. Unconventional Petroleum Research Institute, China University of Petroleum (Beijing), Beijing 102249, China;

2. Beijing Key Laboratory for Greenhouse Gas Storage and CO₂-EOR, China University of Petroleum (Beijing), Beijing 102249, China;

3. College of New Energy and Materials, China University of Petroleum (Beijing), Beijing 102249, China

Abstract: CO₂ flooding has the advantages of easy injection and miscibility in the development of low-permeability reservoirs, but it will inevitably bring about asphaltene deposition in oil displacement, resulting in pore throat blockage of reservoirs, wettability alteration, and permeability reduction. Nanoparticles have great potential in inhibiting asphaltene deposition and are expected to be further used to improve oil recovery in low-permeability reservoirs. In this paper, the mechanism of nanoparticles inhibiting asphaltene deposition is discussed from the perspective of molecular structures. Moreover, the latest progress in relevant research is summarized and the challenges of the research and application are pointed out with prospective predicted. Nanoparticles mainly inhibit asphaltene deposition through adsorption and dispersion. Adsorption depends on the electrostatic attraction between surface charges of the nanoparticles and the strong polar groups of asphaltenes, so that the nanoparticles coat on the surface of asphaltene molecules, eliminating asphaltene deposition. Dispersion is mainly through the grafting of organic chains on the surface of nanoparticles to generate van der Waals force or steric hindrance with asphaltene molecules, thus destroying the self-association between asphaltene molecules and achieving the inhibition on asphaltene deposition. However, the technology is still in the stage of laboratory study, and its large-scale field application is restricted by factors such as the stability of nanofluids, the cost of nanomaterials, and the uncertainty to the environment. The development of stable, economical, and environmentally friendly novel nanofluids is the key to future research, and the establishment of a more precise mathematical model is also an important direction for future exploration.