Owing to superior properties such as temperature resistance and salt tolerance etc., modified polyacrylamide (PAM) as one of the main injected polymers has been widely investigated to enhance oil production in reservoirs. Herein, a novel poly(AM-co-A-b-CD-co-AE) polymer was synthesized by utilizing b-CD and AE to copolymerize with AM and characterized by FT-IR and SEM. Furthermore, the temperature resistance and salt tolerance of poly(AM-co-A-b-CD-co-AE) polymer were explored. The results showed that the presence of the poly(AM-co-A-b-CD-co-AE) polymer better achieved temperature resistance and salt tolerance properties than is the case with PAM, which has potential application for enhancing oil recovery in the high-temperature and high-mineralization oilfield. On the other hand, the inhibition performance of poly(AM-co-A-b-CD-co-AE) polymer as a corrosion inhibitor was evaluated by SEM and electrochemical techniques. SEM observations of the carbon steel surface confirmed the protective role of the corrosion inhibitor. The results of potentiodynamic polarization and EIS measurements on the corrosion inhibition of carbon steel samples in 0.5 M sulfuric acid solutions revealed that the highest inhibition efficiency of it over 90% was obtained, indicating poly(AM-co-A-b-CD-co-AE) polymer acts as a more efficient corrosion inhibitor for carbon steel.

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.

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