Study on a Nonionic Surfactant/Nanoparticle Composite Flooding System for Enhanced Oil Recovery.

The composite flooding system composed of a surfactant and nanoparticles has shown great application potential in enhancing oil recovery. However, at present, these research studies are mainly focused on anionic surfactants. Relatively speaking, alkanolamide (CDEA), a nonionic surfactant, has the characteristics of a small adsorption amount on the rock surface, no cloud point, good temperature resistance, and good salt resistance. However, to the best of our best knowledge, there is no research report on the composite flooding system composed of CDEA and nanoparticles. Therefore, the surfactant/nanoparticle (S/NP) flooding system based on CDEA and nano-SiO2 was studied in this paper. The S/NP flooding system (0.1% CDEA + 0.05% SiO2) was constructed based on the performance in reducing the oil-water interfacial tension (IFT) and the stability of the composite system. The IFT between the S/NP flooding system and the crude oil can reach ultra-low values (3 × 10-3 mN/m), and there is no obvious sedimentation within 72 h. The sandpack flood tests show that the oil recovery rate is increased by 16.8% compared with water flooding and finally reaches 58.2%. Based on micromodel flooding tests, the mechanisms of the S/NP flooding system are studied as follows: the synergistic effect of nanoparticles and surfactants can re-enforce its oil-water interface performance and improve the oil displacement efficiency and the Jamin effect of emulsified oil droplets, combined with the thickening property and retention plugging of nanoparticles, improves the sweep efficiency. As the surfactant and nanoparticle used in this study are commercially available industrial products, the research results have important guiding significance for promoting the industrial application of surfactant/nanoparticle composite flooding technology.