Viscoelastic rodlike surfactant micelles: Rheology and flow through porous media

This dissertation examined two problems posed by the use of rodlike micelle viscoelastic (VES) fluids as fracture fluids in the oil recovery. The first one involves the rheology and dynamics of these rodlike micelles. The linear viscoelastic response of rodlike micelles formed with erucyl bis(hydroxyethyl) methylammonium chloride (EHAC) and KCl was studied as a function of temperature and solvent addition. The apparent activation energy for scission, Escis, was determined to be 81 +/- 8 kJ/mol, decreased to 74 +/- 7 kJ/mol with ethanol addition. With an addition of hexane, a more hydrophobic solvent, the solvent partitions into the micelles inducing phase transition. The study leads to the development of "solvent: temperature" superposition rules to predict the rheology of these fluids at elevated temperatures.; To increase the viscosity of VES fluids, the rheology of hydrophobically-modified polyacrylamide (hmPAM) and rodlike micelles of cetyl trimethyl ammonium bromide (CTAB) and sodium salicylate (NaSal) was studied. hmPAMs were synthesized by micellar polymerization. It was found that hmPAM increased the apparent viscosity of the rodlike micelles fluids at least two fold, but phase separation occurred at polymer concentrations higher than 0.01 wt%.; The second phase of the study involved the flow of rodlike micelles through porous media. The flow was divided into two contributions: (1) entrance flow into porous media and (2) internal flow inside porous media. The entrance flow was studied using CTAB/NaSal micelles and membrane filters. It was found that the micelles formed a filter cake when the solvent flow is less than critical solvent velocity (Vc1). The entry flow is modeled using the theory of polymer entry into pores developed by de Gennes. A second flow transition at a higher velocity, Vc2, the rods are thought to fragment during flow in the porous media. The internal flow inside porous media was studied using small angle neutron scattering (SANS). We showed that SANS could be used for an in situ measurement of the micelles in a silica packed bed. The confinement in the pore space predisposed the micelles to alignment. When the flow was introduced, the alignment was stronger as seen in an anisotropic scattering.