Novel Thermal Stimuli-Responsive Surfactants to Reduce Operation Costs for Chemical Flooding

Abstract Demulsification of produced fluids in chemical flooding is a costive treatment due to the stable emulsion in the presence of injected surfactants. The objective of this study is to develop unique thermal stimuli-responsive surfactant, which reduces interfacial tension (IFT) at high temperature in reservoir for improving oil production and loses effectiveness when temperature decreases to easily break the produced emulsion at low temperature in surface to reduce operation costs. The surfactant formulation was developed by mixing two different surfactants and one has thermal stimuli-responsive group. Compatibility, IFT and particle size measurements were conducted at different temperatures from 90°C to 25°C representing the temperatures from reservoir to surface. Compatibility was performed using Stability Analyzer by recording transmission light intensity. IFT was tested by spinning drop tensiometer. The measurement kept going until the equilibrium IFT was reached. Particle size was obtained using dynamic light scattering instrument. Emulsion was prepared by homogenizer and evaluated by Stability Analyzer. The developed surfactant formulation present unique interfacial properties: high oil/water IFT at low temperature in surface while ultra-low oil/water IFT at high temperature in reservoir. IFT was 10−1mN/m at 25°C and 40°C. The value decreased to 10−3 mN/m when temperature increased to 80°C and 90°C which indicated the synergistic effect between the mixing surfactants at high temperature. This suggests that the formulation has thermal stimuli-responsiveness, which is due to the molecular structure change with the temperature. Other surfactants with similar structures can also be used to develop thermal stimuli-responsive surfactants (TRS). Emulsions using TRS and another surfactant formulation which has low IFT at 25°C were prepared. Results show that the emulsions with TSR separated much faster. These results demonstrate that TRS has good potential for improving oil production in high temperature reservoir due to ultra-low IFT, and the high IFT value at low temperature is beneficial for produced fluids treatment. This work developed thermal stimuli-responsive surfactants by mixing two different surfactants to enhance oil production and to reduce cost for demulsifying produced fluids at surface in chemical flooding operation.