The role of KCl in cationic Gemini viscoelastic surfactant based clean fracturing fluids

KCl, as a kind of counter-ion salt, is often used in cationic viscoelastic surfactant (VES) clean fracturing fluid systems. The interaction between Cl- and VES cationic hydrophilic groups is used to promote the formation of VES micelles, which significantly improves the viscoelasticity, temperature resistance, and shear resistance of cationic VES fracturing fluid. At the same time, KCl is also a widely used inorganic salt clay stabilizer. K+ enters the interlayer of the clay and reduces the hydration expansion of clay by charge attraction. To determine whether Cl- and K+ in KCl can simultaneously play the role of counter-ion and clay stabilizer, we have evaluated the performance of KCl on viscoelasticity, temperature, shear resistance of cationic VES fracturing fluid and clay stability. The interaction of KCl and VES in clay stability was also studied. Results revealed that VES thickener has a clay stabilization effect in cationic VES fracturing fluid system, and the higher the concentration, the better the clay stabilization effect. KCl can not only effectively enhance the viscoelasticity and temperature resistance of cationic VES fracturing fluid, showing a counter-ion performance, but also acted as a clay stabilizer. However, VES and KCl can restrain each other in clay stability and produce antagonistic effects.