In order to improve the damage of hydraulic fracturing flow-back fluid to reservoir and the pollution to environment,the surfactant EA was synthesized by bimolecular nucleophilic substitution reaction with stearic acid and N,N-dimethylaminopropylamine as raw materials and sodium fluoride as catalyst. An CO2 responsive aqueous solution was constructed by mixing sodium salicylate and EA,which could be used as clean fracturing fluid and realize recycling. The reactivity and cyclic reversibility of EA aqueous solution and its compound system with counter ion were evaluated by rheometer. The responsive and reversible transformation mechanism were analyzed from mesoscopic and microscopic levels by electron microscope and molecular dynamics simulation. The results showed that EA aqueous solution and the compound system had good viscosity increasing characteristics to the response of CO2 and pH value,and the viscosity reduction of system could be realized by introducing N2 or high temperature. The solution system had high viscosity increasing rate to CO2 response,fast responsive speed and high viscoelastic modulus,and could realize multiple reversible transformations. Molecular dynamics simulation and freeze electron microscope revealed the formation and transformation mechanism of wormlike aggregates in solution system,which provided a theoretical basis for the recycling of clean fracturing fluid.
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WU Xuepeng, JIANG Shanhong, DAI Caili. Performance and Transformation Mechanism of CO2 Responsive Clean Fracturing Fluid[J]. OILFIELD CHEMISTRY,2021,38(4):608-613.