Environmentally friendly wormlike micelles: Rheological behavior and its application in preparing green fracturing fluid

Abstract

Ionic liquid surfactant (ILS) may be a good alternative to equilibrate the antagonistic relationship between hydrophobicity and water solubility for anionic surfactant. However, the application of ultra-long chain anionic ILS in the viscoelastic surfactant (VES) fracturing fluid was rarely reported up to now. Herein, an ultralong-chain anionic surfactant (abbreviated ChEr) was synthesized from natural erucic acid. As expected, ChEr retained the desirable characteristic of ILSs (melting temperature <100 ℃) and excellent water-solubility (Krafft temperature < 4 ℃). More importantly, ChEr can form elongated wormlike micelles (WLMs) in the presence of inorganic salt potassium chloride (KCl), giving solutions high viscoelasticity. The WLMs solutions were investigated using steady-state and dynamic rheology. Due to the strong van der Waals interaction induced by ChEr's ultra-long hydrophobic tail, zero-shear viscosity (η0) of solutions showed an extraordinarily significant relationship on concentration with an exponent of 8.2, which was more than double the theoretical expected value. The dynamic rheology results demonstrated that as the ChEr concentration increased, the 1:1 ChEr:KCl solution transformed into a gel-like liquid owing to the dense entanglement of WLMs. The salt concentration also had a strong influence on the wormlike micelles. At a KCl to ChEr molar ratio of 2:1, the fluid exhibited the maximum viscoelasticity. Finally, the fracturing fluid system based on ChEr/KCl displayed not only resistance to high temperature (<120 °C) and cyclic shear, but also excellent proppant-carrying and oil-induced gel-breaking capabilities. The present work reveals the remarkable properties of ultra-long chain ILS in forming WLMs and promotes the application of anionic ILS surfactant in the preparation of clean fracturing fluid.