Unravelling the Regulation of Asphaltene Deposition by Dispersants Through Macro-Stability in Micro-Mechanism

The deposition of asphaltenes poses a critical challenge to the petroleum industry, reducing the efficiency of oil wells and, in severe cases, clogging pipelines. Dispersants are widely used to enhance asphaltene stability, but asphaltenes are complex, solubility-defined compounds with variable properties, leading to uncertainties in dispersant microscopic mechanisms, macroscopic effects, and their relationships—requiring further study. This work investigated two anionic dispersants (sodium dodecyl benzene sulfonate (SDBS) and dodecyl benzene sulfonic acid (DBSA)) for dispersing GT asphaltene (GT-ASP, isolated from offshore heavy oil), aiming to improve offshore heavy oil stability. Using an asphaltene–toluene system, it analyzed dispersant effects on GT-ASP stability, particle size, and adsorption and underlying mechanisms. DBSA showed superior performance: at 1000 ppm (w/v), it reduced GT-ASP average particle size from ~160 nm to ~29 nm and increased the onset of the flocculation point (OFP) from 33.5 vol% to 63.0 vol%, driven by chemical adsorption, hydrogen bonding, and π–π conjugation. In contrast, SDBS promoted aggregation: particle size reached 257 nm (1000 ppm (w/v)) and 1271 nm (5000 ppm (w/v)), with OFP at 54.6 vol%, likely due to Na+-induced charge neutralization, insufficient steric hindrance, and “micellar bridges” via SDBS self-aggregation. Finally, this study makes a valuable contribution to both the theoretical guidance and the practical application of asphaltene dispersants.