Nanotechnology Applications in Viscoelastic Surfactant Stimulation Fluids

Abstract

Summary Viscoelastic surfactant (VES) fluids have been used widely in the oil industry as completion and stimulation fluids. The surfactants arrange structurally to form rod-like micelles that increase VES-fluid viscosity for regular fracturing and fracture-packing fluids. However, high fluid leakoff and low viscosities at elevated temperatures have limited VES fluids to hydraulic fracturing and fracture-packing applications. This paper will introduce a nanotechnology application for maintaining viscosity at high temperatures and controlling the loss of VES fluid without generating formation damage. The nanoparticles studied are 35-nm inorganic crystals that display unique surface morphology and surface reactivity. These nanometer-scale particles associate with VES micelles through chemisorption and surface-charge attraction to stabilize fluid viscosity at high temperatures and to produce a pseudofilter cake of viscous VES fluid that reduces significantly the rate of fluid loss and improves fluid efficiency. When internal breakers are used to break the VES micelles, the fluid will lose its viscosity dramatically and the pseudofilter cake will then break into brine and nanoparticles. Because the particles are small enough to pass through the pore throat of producing formations, they will be flowed back with the producing fluids, and no damage will be generated. The results of rheology, leakoff, and core-flow tests will be presented for the VES-fluid systems at temperatures 150 and 250°F.