Switchable Surfactant-Based CO2‑in-Water Foam Stabilized by Wormlike Micelle

Utilizing CO2 switchable surfactant and formation of wormlike micelle, a potential CO2-in-water (C/W) foam fluid concept is proposed, which might give us a fantastic approach to recovering the surfactant composition. For this objective, CO2 responsiveness of N,N-dimethyl oleoaminde-propylamine (DOAPA) and surface activity of DOAPA in the presence of CO2 were verified. After bubbling CO2, aqueous solutions of DOAPA with sodium salicylate (NaSal) at molar ratio 1:1 were created of high apparent viscosity because of the formation of wormlike micelle. The results from 1H NMR, dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryo-TEM) studies indicated that CO2 responsiveness of DOAPA@NaSal was related to DOAPA and a network wormlike structure formed in the solution. DOAPA@NaSal C/W foam stabilized with wormlike micelle displayed good thermal adaptability and thermal stability, and might be expected to be a practical fracturing fluid for coalbed methane extraction. Moreover, DOAPA could be recovered through adjusting pH, and a recovery rate over 90% was obtained in the lab.