Improving surfactant flooding for heavy oil recovery using nano-emulsions

As we continue to deplete light oil reserves for use in transportation, heavy oil is being eyed as a replacement; unlike light oil, however, the refining process is more complex, and even accessing it can be a problem.

Surfactant flooding is a well-established method of heavy oil recovery; by pumping the surfactant into a reserve, the oil and the surfactant create an emulsion. Like a salad dressing that has been untouched for a while, the oil separates out and can be harvested.

Wang et al. studied the use of nano-emulsions in surfactant flooding to increase the efficacy of oil recovery.

“When surfactants are added to [an] oil-sand mixture, the hydrophobic tails can penetrate into the oil phase to reduce the heavy oil viscosity and oil-water interfacial tension,” said author Wanying Wang. “Consequently, the oil can be effectively removed from the oil-sand mixtures.”

Compared to traditional emulsions used in oil recovery, the smaller drops of nano-emulsions exhibit more uniform droplet dispersion and long-term stability. The researchers flooded crude oil-and-sand samples with combinations of three different surfactants and studied the interface forces of these nano-emulsions.

The team found that combining a nonionic surfactant, fatty alcohol polyoxyethylene ether (AEO-7), and an anionic surfactant, sodium dodecyl sulfate (SDS), showed the best oil-washing efficiency.

“This is attributed to the synergistic stabilization of the oil-water interface by AEO-7 and SDS … which promotes oil peeling and enhances oil–sand separation,” Wang said.

Wang said they hope to apply their findings to the oil recovery industry in the next decade or so.

“This study can provide a robust, mechanics-guided methodology of formulating efficient nano-emulsions for enhanced heavy-oil recovery and offer mechanistic insights applicable to different reservoir conditions and rock compositions, thus supporting the rational design of advanced chemical systems for the efficient development of oil reservoirs,” Wang said.

Source: “On the effects of surfactant charge on interfacial stability in nano-emulsions,” by Wanying Wang, Zhe Li, Bobo Zhou, Yibo Kong, Yilu Zhao, Yulong Cheng, Xuesong Yang, Lei Wang, Yaowen Xing, and Xiahui Gui, Physics of Fluids (2026). The article can be accessed at https://doi.org/10.1063/5.0322959 .