Application of surfactants on asphaltene stability in heavy oil by interfacial tension approach

Abstract

ABSTRACT The objective of this work is to understand the effect of asphaltene on surface properties including interfacial tension (IFT) and reach a specific surfactant in order to inhibit asphaltene precipitation in heavy oils. IFT experiments are implemented by Pendant Drop method and effective mechanisms causing IFT fluctuations are interpreted. The uniform trend of IFT for water/synthetic oil diminished at 25 volume percent of n-heptane which is attributed to asphaltene precipitation onset. Repetition of the experiment with 31 volume percent of n-heptane and real oil sample of field “S” resulted in asphaltene precipitation onset point. This change is justified by different density of synthetic and real oil samples. In addition, three surfactants of L-DBSA (linear dodecyl-benzene-sulfonic acid), B-DBSA (branched dodecyl-benzene-sulfonic acid), and DR (dodecyl resorcinol) are used to retard the asphaltene precipitation onset. Due to special chemical structure and polar group of DR, it is a weaker surfactant than DBSA in terms of inhibition of asphaltene precipitation. Furthermore, chemical structure and spatial avoidance of branches in B-DBSA causes little adsorption to asphaltene molecules and insignificant stability that eventually postpones the onset of asphaltene precipitation at lower degree compared to L-DBSA. When surfactants are introduced, the thin film of asphaltene formed on water-oil interface exhibits enhanced stability with the order of L-DBSA>B-DBSA>DR. Results show 0.25 wt% of L-DBSA can considerably delay the onset point that remedies the problem of asphaltene precipitation in heavy oil fields to great extent.