Correlation of Asphaltene Solvation with Stability of Crude Oil Emulsion Using Scaling Equations

Abstract

Due to the simplicity of scaling equations and its applicability to colloid chemistry, the scaling theory is widely used in studying emulsion properties such as force profiles. Understanding asphaltene chemistry and the fundamental mechanisms of colloid formation has been the driving force behind much petroleum research in recent years. Scaling equations were developed for the studied samples for correlation of asphaltene solvation with stability of crude oil emulsions. The researcher used five crude oil emulsion samples from Niger Delta region of Nigeria for their study. Correlations were made for viscosity and percentage water resolved by varying the volume concentration of toluene in heptol mixture that was used as solvent for the asphaltene re-dissolution. The study shows that tuning the composition of heptol allows fine control of colloidal forces between asphaltene surfaces in an organic solvent and therefore determines the stability state of the emulsion. Statistically derived correlation equations provide for a range in the aromaticity of the crude medium for which an optimum stability is observed and therefore gives good understanding on the control of emulsion stability. Since attractive van der Waals forces are omnipresent in asphaltene/heptol system, it was interesting to investigate the variation of van der Waals forces with the solvent composition. This study indirectly investigated this force, as variation in viscosity of the emulsion since the solvation state of asphaltene was responsible for the varied viscosity of the emulsion. The study further shows that emulsion inversion can be achieved by adjusting the concentration of surfactant.