Impact of spacer on rheological properties of polyoxyethylene cationic surfactant-polymer solution

Enhanced oil recovery (EOR) include all those methods in which an external source of energy are used to recover additional oil after water flooding. Thermal EOR, gas EOR and chemical EOR are three major tertiary recovery techniques. In chemicals EOR, different chemicals such as surfactants, polymers, and alkalis are injected to alter the fluid-fluid and rock-fluid interactions which improve the oil recovery. Polymers are injected to improve the viscosity of the injected water. Surfactants are used to reduce the interfacial tension between water and oil. In a few cases, surfactants and polymers are co-injected to achieve high viscosity and low interfacial tension, simultaneously. In this work, we synthesized three polymeric cationic gemini surfactant containing different spacer length and rigidity. The rheological properties of these surfactants with the commercially available acrylamide-based copolymer was investigated using Discovery hybrid rheometer (DHR-3) at various temperatures. The viscosity and storage modulus reduced by increasing the concentration of the surfactant. It was also observed that the spacer length and rigidity affect the rheological properties of the surfactant-polymer solution. The addition of surfactant with a rigid spacer causes more reduction in the viscosity of the polymer. However, at high shear rates, the effect of added surfactant was negligible. For field applications, the rigidity of the spacer becomes less important as for as rheological properties are concerned due to high shear rate.