The mechanism responsible for lowering interfacial tension between heavy crude oil and betaine solutions

Abstract

To clarify the mechanism responsible for the reduction of interfacial tension (IFT), the dynamic and equilibrium IFTs of different betaine solutions against n-alkanes, kerosene, heavy oil fractions model oil and crude oil have been investigated by spinning-drop interfacial tensiometer. The experimental results show that the synergism for lowering IFT between heavy crude oil and betaine solutions are controlled by two main factors. One is “size compatibility” between surfactant molecules and surface-active substances in crude oil. The other is the optimized ratio of crude oil fraction to betaine. The betaine molecules with large size of hydrophilic group can form compact interfacial film with surface-active fractions in heavy crude oil by mixed adsorption. Therefore, betaines with large hydrophilic groups show an apparent synergism with heavy crude oil in lowering IFT and can produce ultralow IFT value at optimized concentration.