Molecular Insights into the Effect of Salinity on the Stability of Water/Oil Interface with Model Asphaltene and Non-Ionic Surfactants

29 Pages Posted: 25 Apr 2022

See all articles by Xiaoyu Sun

Xiaoyu Sun

affiliation not provided to SSRN

Hongbo Zeng

University of Alberta - Department of Chemical and Materials Engineering

Tian Tang

University of Alberta

Abstract

Water or brine always co-exist with oil during petroleum production, often in the form of emulsions which can be stabilized by surface-active components such as asphaltenes. Polymeric demulsifiers were frequently applied to destabilize the water/oil interface. To understand the demulsification mechanisms of water/oil emulsion, it is important to understand the effect of salinity on the stability of water/oil interface with adsorbed asphaltenes and polymeric demulsifiers. In this work molecular dynamics simulations were performed on water/heptol interfaces under the influence of a model asphaltene (VO-79), a polymer demulsifier (PEO5-PPO10-PEO5) and varying concentration of NaCl. Potential of mean force calculation indicated that when NaCl was added the magnitude of the adsorption free energy for VO-79 had insignificant changes and that for the polymer increased. In the absence of VO-79, the interfacial tension (IFT) at water/heptol interface first increased upon increasing the NaCl concentration to 6 wt.% and then decreased. The initial increase was attributed to the negative surface excess of salt while the subsequent decrease was due to the evident aggregation of salt ions in the water phase. With both polymer and VO-79 at the interface, the effect of salinity on IFT followed the same non-monotonic trend, except that the transition occurred at a lower concentration, which was caused by the mutual influence of H-bonds between adsorbates and water, and the surface excess of salt. The results provide useful insights into the effect of salinity on the stabilization and destabilization of water/oil interface.

Keywords: Molecular simulations, Non-ionic surfactant, Water-in-oil emulsions, Demulsification, Effect of salt

Suggested Citation

Sun, Xiaoyu and Zeng, Hongbo and Tang, Tian, Molecular Insights into the Effect of Salinity on the Stability of Water/Oil Interface with Model Asphaltene and Non-Ionic Surfactants. Available at SSRN: https://ssrn.com/abstract=4092393 or http://dx.doi.org/10.2139/ssrn.4092393

Xiaoyu Sun

affiliation not provided to SSRN ( email )

No Address Available

Hongbo Zeng

University of Alberta - Department of Chemical and Materials Engineering ( email )

Canada

Tian Tang (Contact Author)

University of Alberta ( email )

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