Enhancing the Performance of Viscoelastic Surfactant Fluids Using Nanoparticles

Abstract Viscoelastic surfactant (VES) based fluids are used in many applications in the oil industry. Their viscoelastic behavior is due to the overlap and entanglement of long wormlike micelles. The growth of these wormlike micelles depends on the charge of the head group, salt concentration, temperature, and the presence of other interacting components. The problem with these surfactants is that they are expensive and used at temperatures less than 200°F. The viscoelasticity of nanoparticle-networked VES fluid systems were analyzed by rotational and oscillatory viscometers. Apparent fluid viscosities were measured by using 2–4 vol% amidoamine oxide surfactant in 13 to 14.2 ppg CaBr2 brines and 10.8 to 11.6 ppg CaCl2 brines at different temperatures up to 275°F and a shear rate of 10 s−1. The nanoparticles evaluated were MgO and ZnO at 6 pptg concentration. In addition, the effect of different nanoparticle concentrations (0.5 to 8 pptg) and particle size on the viscosity of VES fluid was investigated. The oscillatory shear rate sweep (100 to 1 s−1) was performed for the 4 vol% VES in 14.2 ppg CaBr2 from 100 to 250°F. This study showed that the addition of nanoparticles improved the thermal stability of VES micellar structures in CaBr2 and CaCl2 brines up to 275°F and showed an improved viscosity yield at different shear rates. Micron and nano-size particles have potential to improve the viscosity of VES fluids. Lab tests show for VES micellar systems without nanoparticles, the dominant factor is the viscous modulus but when nanoparticles are added to the system at 275°F the elastic modulus becomes the dominant factor. These positive effects of nanoparticles on VES fluid characteristics suggest that these particles can reduce treatment cost and will extend the temperature range of the surfactants to 275°F.