Equilibrium and Temporal Evolution of Asphaltene Nanoaggregates during Dynamic Heteroaggregation with Polysaccharides

Asphaltene blockage and microbiologically induced corrosion (MIC) in oil pipes pose substantial flow assurance challenges, but their interrelationship remains poorly understood despite extensive individual research efforts. This study utilized molecular dynamics simulation and machine learning techniques to elucidate the effects of alginate, a representative biofilm polysaccharide associated with MIC, on asphaltene aggregation. Results underscored the ability of alginates to disperse large asphaltene nanoaggregates into smaller ones with more pronounced dispersion effects at higher concentrations. This was achieved through forming asphaltene–alginate heteroaggregates wherein asphaltene nanoaggregates were tightly wrapped by cross-linked alginate chains stabilized by Na+ bridging. The presence of alginates significantly increased the solvent accessible surface area (SASA) of asphaltenes, while the heteroaggregation process resulted in abundant hydroxyl and carboxyl groups coating the surface of the asphaltene nanoaggregates. Furthermore, this study showed that the time-varying asphaltene aggregation parameters such as nanoaggregate number, intermolecular contact number, and SASA could be accurately predicted by alginate structural properties using optimized random forest models built from 3636 data sets extracted from molecular trajectories (R2 = 0.9628–0.9827). This enabled fast prediction of asphaltene aggregation when the polysaccharide composition and concentration changed during the MIC process. These findings provided theoretical support for developing strategies to address asphaltene-related issues in the presence of a biofilm polysaccharide.