The contact of acid with crude oil generates a reaction product known as acid-sludge which has been interpreted as polymerized asphaltenes due to Friedel-Crafts reactions. A size-exclusion chromatographic analysis of crude oils and fractions showed, however, that acid-sludge is composed of small molecules. The greatest increase in molecular weight was observed for the nonpolar fractions. The results could be explained by assuming surfactant-like behaviour of protonated basic crude oil components. Aggregate formation, therefore, explains the higher molecular weights observed.
Rietjens, M., & Nieuwpoort, M. (2001). Analysis of crude oil-acid reaction products by size-exclusion chromatography. Fuel, 80(1), 33–40. https://doi.org/10.1016/S0016-2361(00)00073-9