Examining and influencing order in the flow of worm-like micelles

Surfactants are widely used as viscosity modifiers or thickening agents in the food, personal care, and pharmaceutical industries. In the energy industry, they are used as hydraulic fracturing fluids to increase oil and gas recovery, where their usage is complicated by their propensity to align and/or band under shear or confinement. To enable the study of the behavior of these micelles in porous media, a series of silicon-and-glass microfluidic cells capable of withstanding pressure drops up to 400 psi were constructed and quantified with particle-imaging velocimetry (PIV). In-situ concentration studies were performed by tagging the micelles with hydrophobic dyes. Accumulation of surfactant in the porous media micromodels was examined as a function of flowrate and surfactant species, and two different accumulation processes are described. Recent work in this field has examined the shear-banding and phase separation in conventional rheological geometry. However, this work has the advantage of being able to measure surfactant accumulation in real-time in a geometry that more closely mimics the environment in which it is typically used. Furthermore, the role of hydrophobically modified polymers in controlling ordering is examined.