Sodium fatty alcohol polyoxyethylene ether carboxylate/cationic surfactant binary system for high-salt oil reservoir

High salinity has been a major challenge in oil recovery. Here, two binary systems composed of sodium fatty alcohol polyoxyethylene ether carboxylate (AECM) and cationic surfactants, cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPyCl) were developed. Their fundamental properties; namely, oil/water interfacial tension, wettability, emulsification, adsorption, and oil-washing were investigated and compared. The results showed that both AECM–CTAB (4:6–7:3, m/m) and AECM–CPyCl (5:5–6:4, m/m) could decrease oil/water interfacial tension below 10⁻² mN/m. Even the total salinity was close to 200,000 mg/L after 7 days of quartz sand adsorption, showing a good interfacial activity and excellent anti-adsorption properties. All these compound drives could effectively change the wettability of the glass surface, which reduced the contact angle to a minimum of 54.76°. In addition, the emulsification time could reach up to 24 h at 85°C, with excellent emulsification performance at high temperatures. The oil washing efficiency could reach 74.68% after 48 h. According to our comprehensive analysis, the best formulation was obtained at AECM/CTAB ratio of 5:5.