β‑Cyclodextrin-Functionalized Hydrophobically Associating Acrylamide Copolymer for Enhanced Oil Recovery

Acrylamide copolymer in the chemical flooding process plays a significant role in the field of tertiary recovery for enhanced oil recovery. Allyl-β-cyclodextrin and octadecyl dimethyl allyl ammonium chloride are utilized to react with acrylamide to synthesize a novel cyclodextrin-functionalized hydrophobically associating acrylamide polymer (HCMPAM) by redox free-radical polymerization. The microstructure of HCMPAM is the spatial network characterized by Fourier transform infrared spectroscopy and atomic force microscopy, and the thermal stability of HCMPAM is investigated by thermal gravimetic analysis. In the performance evaluation experiments, HCMPAM demonstrates superior properties compared to the high molecular weight partially hydrolyzed polyacrylamide on the aspects of salt tolerance, temperature resistance, shear resistance, and surfactant compatibility. It was found that the viscosity of 2000 mg/L HCMPAM reaches a maximum at 80 °C, and it could maintain 45.7% viscosity retention rate at 120 °C under the conditions of 20000 mg/L NaCl, 2000 mg/L CaCl2, and 10 s–1 shear rate. The viscosity can recover immediately with a slight decrease to the primary value during repeated revisable shear (100 s–1–0). In addition, the flooding mechanism of mixed flooding of HCMPAM and surfactant is put forward by the interaction between them. The simulative tertiary oil recovery tests signify that HCMPAM can remarkably enhance 5.7–9.4% of oil recovery ratio, especially while HCMPAM is used after HPAM flooding. These features indicate that HCMPAM has a great potential application for enhanced oil recovery, especially in high-temperature and high-mineralization oil fields.