Quaternary Ammonium Gemini Surfactants Used in Enhanced Oil Recovery: Synthesis, Properties, and Flooding Experiments

Abstract

In this work, quaternary ammonium gemini surfactants with different spacers and lipophilic tails were synthesized by using imidazole and halogenated hydrocarbons as raw materials. The surfactants were characterized by EA, IR, and ESI-MS. Physico-chemical properties including critical micelle concentration (CMC), surface tension at CMC (γ_CMC), saturated adsorption amount (Γ_max), occupied area per molecule (A_min), standard free energy of micellization (ΔG⁰_m) and adsorption (ΔG⁰_ads), as well as the oil/water interfacial tension were completely studied. The prepared surfactants could efficiently lower the interfacial tension at water/air interfaces and oil/water interfaces. The results indicate that the ability of reducing the surface tension was affected by the surfactant arrangement, which could be further adjusted by a spacer and lipophilic tail. Accordingly, four surfactants were chosen as the representatives to evaluate the displacement efficiency in flooding experiments via using the authentic sandstone microscopic model.