The
aggregation behaviors of asphalt on the hydrate surface with
different surfactant coverages were studied by molecular simulations.
The molecular polarity index of asphalt (10.47 kcal/mol) is higher
than that of Span 80 (8.19 kcal/mol). Asphalt is easier to occupy
the binding sites between Span 80 and hydrate. Asphalt mainly depends
on the π–π interaction to form aggregates. The
dispersion interaction up to −114.17 kcal/mol is the main factor
to maintain the asphalt aggregate stability. With the increase of
surfactant coverage, the polar groups of asphalt are easier to associate
with each other, promoting the formation of larger asphalt self-aggregates.
The self-aggregation increases the complexity of asphalt stacking,
and the proportion of edge-to-face stacking types increases from 40
to 60%. When the Span 80 molecule number reaches 12, the diffusion
coefficient of asphalt is only (2.31 ± 0.5) × 10–8 cm2/s. Asphalt with low diffusivity can provide new sites
for hydrate nucleation. The results are helpful to understand the
aggregation mechanism of asphalt on the hydrate surface. Increasing
the concentration of surfactant only is not a good solution to solve
blocking-pipeline problems. We need to use surfactant reasonably and
give full play to the anti-agglomerant effect of asphalt itself.