Viscoelastic surfactants can provide viscoelastic properties in brines at high temperatures (higher than 230°F). Recent studies have shown the advantages of use nanoparticles in VES fluid systems. The nanoparticles have large surface area as well as unique surface morphology and surface reactivity. They can strengthen the micelle-micelle interactions. A small concentration of these particles can maintain viscosity at higher temperatures (up to 300°F) and decrease the rate of VES fluid leakoff (Huang, Crews and Willingham, 2008).
The viscoelasticity of nanoparticle-networked VES fluid systems was analyzed with a HP/HT viscometer. A series of rheology experiments have been performed by using 4 vol% amidoamine oxide surfactant in KCl, NaCl and CaBr2 brines at temperatures up to 275°F and a shear rate of 10 s-1. The nanoparticles evaluated were MgO and ZnO at the concentration of 6 pptg. In addition, the effect of different nanoparticle concentrations (0.5 to 10 pptg) on the viscosity of VES fluid was investigated. The oscillatory shear rate sweep (100 to 1 s-1) was performed from 100 to 200°F. The effect of an internal breaker on the viscosity of VES micelles was examined.