Study of the formation and solution properties of worm-like micelles formed using both N-hexadecyl-N-methylpiperidinium bromide-based cationic surfactant and anionic surfactant.

The viscoelastic properties of worm-like micelles formed by mixing the cationic surfactant N-hexadecyl-N-methylpiperidinium bromide (C16MDB) with the anionic surfactant sodium laurate (SL) in aqueous solutions were investigated using rheological measurements. The effects of sodium laurate and temperature on the worm-like micelles and the mechanism of the observed shear thinning phenomenon and pseudoplastic behavior were systematically investigated. Additionally, cryogenic transmission electron microscopy images further ascertained existence of entangled worm-like micelles

Study on the Relationship between Emulsion Stability and Droplet Dynamics of a Spontaneous Emulsion for Chemical Enhanced Oil Recovery

Spontaneous emulsion (SE) has attracted increasing attention, especially in the development of low-permeability reservoirs (with an average throat radius of 0.1-2 µm) for enhanced oil recovery. In this work, based on multiple light scattering principles, the relationship between emulsion stability and the droplet dynamics of SEs was investigated. The results showed that the synergistic effect of surfactant and polymer was crucial for oil emulsification in brine, since the stability of the emulsion was greatly improved. The emulsion stability and droplet dynamics depend on the temperature, concentration, and type of emulsifier. The optimal combination system had the lowest Turbiscan stability index value, and the emulsion stability time was more than 2000s. The average droplet size was 1.50 µm, and the droplet migration rate was 7.21 mm/h. The stability of the emulsion was resulted from the microscopic droplet dynamics. By reducing the migration rate of the droplets, stability of the emulsion can be obtained. Finally, the stability and droplet dynamics mechanism of the system were explained by using a schematic representation of the various equilibriums in the spontaneous emulsification flooding system

Temperature effect plots.

<p>(a) The zero shear viscosity as a function of temperature for the 70 mM C₁₆MDB/40 mM SL solution; (b) the frequency sweep of 70 mM C₁₆MDB/40 mM SL system at different temperatures.</p

Cryo-TEM images.

<p>(a) Cryo-TEM image of the 70 mM C₁₆MDB/35 mM SL solution; (b) Cryo-TEM image of the 70 mM C₁₆MDB/40 mM SL solution.</p

Shear stress with different concentration of SL at a fixed C₁₆MDB concentration of 70 mM.

<p>Shear stress with different concentration of SL at a fixed C₁₆MDB concentration of 70 mM.</p

Various rheological parameters calculated for the sample of 70 mM C₁₆MDB/40 mM SL at different temperatures.

<p>Various rheological parameters calculated for the sample of 70 mM C₁₆MDB/40 mM SL at different temperatures.</p

Energy calculation plots.

<p>(a) An Arrhenius plot of ln<i>τ</i>_R as a function of 1/T for the 70 mM C₁₆MDB/40 mM SL solution; (b) the plot of ln (G″_min/G₀) as a function of 1/T.</p

Steady rheology plots.

<p>(a) Steady rheology plots for 70 mM C₁₆MDB with different SL concentrations at <i>T</i> = 25°C; (b) Variations of zero-shear viscosity () as a function of different SL concentrations for the 70 mM C₁₆MDB.</p

Dynamic oscillatory plots.

<p>(a) Variations of G′ and G″ as a function of frequency (<i>ω</i>) in aqueous 70 mM C₁₆MDB/35 mM SL solution; (b) Cole–Cole plots (solid lines indicate the best fitting of Maxwell model).</p

Shear-rate dependence of the steady-shear viscosity and frequency dependence of the complex viscosity for the 70 mM C₁₆MDB/35 mM SL solution.

<p>Shear-rate dependence of the steady-shear viscosity and frequency dependence of the complex viscosity for the 70 mM C₁₆MDB/35 mM SL solution.</p