Abstract: Three cationic surfactants, tetradecyl dimethyl hydroxypropyl ammonium bromide (C₁₄-2-1-1), cetyldimethyl hydroxypropyl ammonium bromide (C₁₆-2-1-1) and octadecyl dimethyl hydroxypropyl ammonium bromide (C₁₈-2-1-1), were synthesized from long-chain brominated alkanes and tertiary amines. The critical micelle concentration (cmc) values and surface tensions of the three cationic surfactants were measured, and C₁₈-2-1-1 was selected as the viscoelastic surfactant for fracturing fluid. By configuring viscoelastic micellar solution of the additive sodium salicylate (NaSal) and C₁₈-2-1-1 as a viscoelastic surfactant (VES) fracturing fluid, we can draw a conclusion that the best formula of the fracturing fluid is 2.5% mass fraction of C₁₈-2-1-1+1.0% mass fraction of NaSal, and the viscosity can be up to 489 mPa·s in the VES fracturing fluid. The performance research shows that the VES fracturing fluid is viscoelastic, the liquidity index n' is 0.23062 and the consistency index K is 19.49. At the shear rate of 170 s^-1, the VES fracturing fluid owns good temperature resistance and shear resistance. When the temperature reaches 90.0 ℃, the viscosity of the VES fracturing fluid is 40 mPa·s. After 1 hour of continuous shear, the viscosity of the VES fracturing fluid can still remain 30 mPa·s. The free settling rate of 380～830 μm ceramsite in the formula fracturing fluid is 0.0516 cm/min, which can effectively carry proppant. It breaks up automatically when meeting kerosene and the residue content keeps low after it, which leaves a low damage rate of 4.19% to the permeability of the core matrix. It has a certain value in the field of oil and gas resources exploitation.

Key words: Fracturing fluid, Cationic surfactants, Viscoelasticity