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-SiO
2
was studied in this paper. The S/NP
flooding system (0.1% CDEA + 0.05% SiO
2
) 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.