(351b) A Gemini-like Viscoelastic Surfactant System with pH Adjustable and High Salt Tolerance Properties Applied in the Area of Fracturing Fluid

In order to efficiently increase the productivity of unconventional oil and gas reservoirs, hydraulic fracturing has become a popular method to achieve this purpose. Many studies have focused on fracturing fluids like slick water, polymer-based fluids, and viscoelastic surfactants. For promising fracturing fluid, it should exhibit outstanding salt tolerance, temperature tolerance and excellent sand carrying capacity. Among those fluids, viscoelastic surfactant (VES), which has both hydrophilic head and long hydrophobic chain in the structure, has attracted growing interest due to its self-assembly of the structure into network of wormlike micelles in aqueous solutions that can increase the ability to carry sand, be easy to prepare and environmentally friendly. In this study, a gemini-like viscoelastic surfactant system was prepare by a mixture of long chain surfactant and hydrotrope with low concentration (~2 wt%) in water. By adjust the pH, this promising material shows pH tunable ability and reversibility. The viscosity can achieve to around 100000 mPa s by changing pH from 6 to 9. When salt is introduced, this VES system can hold sand for over 1 day even with salt concentration up to ~20 wt% at certain pH condition. Also, temperature effect and stability have been studied to find out the working range of this novel fluid. Besides, the chemical structure and characterization, viscosity and viscoelastic properties and sand settling were also included in this study.