Preparation and properties of responsive channeling prevention system for tight oil reservoir CO2 flooding

CO2-responsive worm-like micelle (CO2-TWMS) was constructed by mixing CO2-responsive monomer N,N-dimethyl oleic amide propyl tertiary amine (DOAPA) with tertiary amine structure, which was prepared from 3-dimethylaminopropylamine (NNDP) and oleic acid, with anionic surfactant sodium p-toluenesulfonate (SPTS). The responsiveness of the system was characterized by the changes in conductivity, chemical structure and micro-morphology before and after its contact with CO2. The anti-channeling performance as well as the mechanism of the system were analyzed by combining the changes in surface activity, pressure, and recovery efficiency in the process of CO2 displacement in dense matrix/crack medium and CO2-TWMS channeling prevention. The results showed that CO2-TWMS system with n(SPTS)∶n(DOAPA)=1∶1 exhibited the highest viscosity of 4125 mPa·s. CO2 and N2 could stimulate reversible changes in electrical conductivity between 0.90 and 1.95 mS/cm, inducing the micromorphology transformation between wormlike and spherical micelles. In addition, CO2 reduced the critical micelle concentration from 0.63 mmol/L to 0.25 mmol/L, and the lowest surface tension from 30.2 mN/m to 29.1 mN/m. The adsorption efficiency and efficacy of the system at the gas-liquid interface were enhanced, which was conducive to the formation of micelles. In the dense matter-fracture medium, CO2 induced wormlike micelle formation, increased the pressure difference during displacement, expanded the CO2 displacement sweep efficiency, and increased the recovery rate by 22.6%. © 2024 Fine Chemicals. All rights reserved.