High‐viscoelastic graft modified chitosan hydrophobic association polymer for enhanced oil recovery

Abstract

AbstractThe conventional partially hydrolyzed polyacrylamide (HPAM) is greatly restricted by its single linear molecular structure in oil reservoirs with severe reservoir conditions such as high temperature and high salt. In this article, the chitosan (CS) grafted imidazoline monomer copolymer (CS‐g‐AM/AA/NIDA) was prepared from N‐maleyl CS (N‐MCS), acrylamide (AM), acrylic acid (AA), 1‐(2‐N‐acryloylaminoethyl)‐2‐oleoyl imidazoline (NIDA) by free radical copolymerization. The structure was determined by means of Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, scanning electron microscope, thermal gravimetric analysis, and so forth, which confirmed the successful preparation of the copolymer with good thermal stability. Under the same conditions, compared with HPAM and copolymer CS‐g‐AM/AA, CS‐g‐AM/AA/NIDA greatly increased the viscosity of the aqueous solution and exhibited excellent shear stability (viscosity retention rate 15.62, 4.91, and 11.54% at 510 s−1), temperature resistance (the viscosity retention rate reached 50.89, 24.50, and 36.59% at 120°C) and salt resistance (14,000 mg/L NaCl: viscosity retention rate up to 17.27, 8.26, and 14.60%). In addition, core flooding experiments showed that oil recovery could be enhanced by up to 8.08% by CS‐g‐AM/AA/NIDA. As a natural polymer material, CS has hardly been reported for polymer flooding, and it is expected to replace general polymers in tertiary oil recovery.