Interfacial Dilational Properties of Acidic Model Oil and Chemical Flooding Systems

Abstract

The interfacial dilational properties of lauric acid model oil and chemical flooding systems have been investigated by means of longitudinal method. The influences of acid on the dilational viscoelasticity of partly hydrolyzed polyacrylamide (HPAM) and anionic surfactants (4,5-diheptyl-2-propylbenzene sulfonate 377 and Gemini surfactant C₁₂COONa-p-C₉SO₃Na) have been expounded. The results show that lauric acid concentration is an important factor in controlling the dilational properties of mixed-adsorption layer. The addition of small amounts of lauric acid to solutions of anionic surfactant appears to increase the dilational modulus, while the superfluous addition could decrease the dilational modulus mainly due to the weakening of strong interaction among long alkyl chains of surfactant molecules. The polymer plays different roles in influencing the nature of adsorbed layers at different lauric acid concentrations: at low concentration, the addition of polymer perhaps weakens the hydrophobic interactions of lauric acid molecules, which results in decreasing the dilational modulus of adsorbed layer. At high concentration, the addition of the polymer increases the dilational modulus due to hydrophobic interactions between polymer and lauric acid molecules. At the same time, the mixed adsorbed layer shows low frequency due to the slow diffusivity of polymer molecules. The addition of lauric acid to polymer-surfactant system will further increases diffusion-exchange process between the interface and the bulk, which consequently leads to the decrease in dilational modulus.

Keywords:

• 4,5-Diheptyl-2-propylbenzene sulfonate
• dilational modulus
• dilational phase angle
• gemini surfactant
• interface
• lauric acid
• partly hydrolyzed polyacrylamide