Abstract:

Fluorocarbon surfactant as the highest surface active surfactant shows a good potential in enhanced oil recovery area. The dilational rheological properties of perfluorooctane sulfonamide dimethyl ammonium ethanol sulfonate(FS) at the oil/water interface were investigated using the oscillating barriers method at low frequency(0.033~0.1 Hz). Many factors, such as the oscillating frequency, bulk concentration and salts, greatly affect the dilational rheological properties. The results reveal that the dilational modulus and elasticity increase and the dilational viscosity slightly increase as the dilational frequency increases. The dilational modulus passes through a maximum value with the FS concentration increasing. Additionally, adding a moderate concentration of NaCl can increase the FS dilational modulus, while adding CaCl₂ or MgCl₂ yields opposite results, and the concentration of CaCl₂ or MgCl₂ reaches to 0.05% and 0.1%, respectively, tanθ is less than 45°.

Key words: fluorosurfactant, oil-water interface, dilational viscoelastic properties, oscillating barriers method