Synthesis and characterization of a graft-modified copolymer for enhanced oil recovery

A graft-modified copolymer (cWL-g-A) was synthesized using Welan Gum (WLG), acrylamide, acrylic acid, and 0-20 via free-radical copolymerization to be well applied for enhanced oil recovery. The chemical structure of the copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetry (TG) and scanning electron microscopy (SEM). The long-term stability, rheology, adsorption, temperature and salt resistance of the copolymer were investigated. The cWL-g-A solution showed superior temperature and salt resistance in comparison with partially hydrolyzed polyacrylamide (HPAM), due to the hydrophobic association of main polymer chain. Particularly in high salinity (230,000 mg/L) solutions, cWL-g-A showed a better antiaging performance at three different temperatures (25, 50 and 65 degrees C). Oil recovery yielded by cWL-g-A was 14.18% higher than that yielded by HPAM, as known from polymer flooding tests. These results elucidated that cWL-g-A synthesized herein was superior to HPAM in high-salinity and medium-high temperature oil reservoirs.