We provide a review of our recent work on the development of a multi-scale simulation methodology to calculate the rheology and flow of wormlike micelles. There is a great need for understanding the link between the detailed chemistry of surfactants, forming wormlike micelles, and their macroscopic rheological properties. We show how this link may be explored through particle simulations. First, we calculate the mechanical properties of small units of wormlike micelles from atomistic molecular dynamics simulations. These mechanical properties are subsequently used in a coarse-grained Brownian dynamics model, where the persistence length is the smallest length scale. We show that the non-Newtonian rheology of wormlike micellar systems can be accurately determined from our simple mesoscopic simulation model. Finally, we show that this mesoscopic model can be used to study the flow of wormlike micelles in contraction-expansion geometries.

Viscoelastic wormlike micelles are formed by surfactants assembling into elongated cylindrical structures. These structures respond to flow by aligning, breaking and reforming. Their response to the complex flow fields encountered in porous media is particularly rich. Here we use a realistic mesoscopic Brownian Dynamics model to investigate the flow of a viscoelastic surfactant (VES) fluid through individual pores idealized as a step expansion-contraction of size around one micron. In a previous study, we assumed the flow field to be Newtonian. Here we extend the work to include the non-Newtonian flow field previously obtained by experiment. The size of the simulations is also increased so that the pore is much larger than the radius of gyration of the micelles. For the non-Newtonian flow field at the higher flow rates in relatively large pores, the density of the micelles becomes markedly non-uniform. In this case, we find that the density in the large, slowly moving entry corner regions is substantially increased.

Recently there has been a great deal of attention, from researchers both in academia and in industry, focused on the rheological properties of solutions of viscoelastic wormlike micelles formed by surfactants. It is particularly vital to understand the properties of these solutions with regard to their flow in porous media, given their application to the recovery of hydrocarbons from subterranean formations. In this study a realistic mesoscopic Brownian dynamics model has been utilized to investigate the flow of viscoelastic surfactant (VES) fluid through individual pores with sizes of around one micron. In particular the influence of micelle size, pore geometry and flow rate on the ability of worms to pass through the pores was studied. The ways in which these parameters influence the conformational properties of the worms and the spatial distribution of micelles inside the simulation cell was also investigated. Despite the observation that the density and length distributions became non-uniform at higher scission energy, the distribution of breaking and fusion events remained spatially uniform.