Amphiphile adsorption on asphaltene particles: adsorption isotherms and asphaltene stabilization

Amphiphiles are frequently used to prevent asphaltene precipitation in reservoir rocks and wellbore tubing. These substances can solubilize the asphaltenes otherwise insoluble under production conditions. In the asphaltene stabilization, the strength of the asphaltene–amphiphile interactions plays a major role. In this study, the adsorption of three amphiphiles on asphaltene particles is studied and correlated with their activity as stabilizers of asphaltenes. The isotherms of these amphiphiles indicate an adsorption process in two steps: in the first step, the amphiphiles are adsorbed through the interactions with the surface of the asphaltene particles; in the second step, the interactions between adsorbed amphiphiles become predominant and the formation of aggregates on the surface begins. The flocculation measurements show that there is a direct correlation between the maximum surface excess concentration of the amphiphile and its activity as stabilizer. It was also found that the effectiveness of the amphiphiles is strongly influenced by the nature of the asphaltene particles: under the same conditions the effectiveness is lower for the more polar and less stable asphaltenes.