Comb-shaped polyzwitterion with surface-activity obtained via N-maleoyl chitosan-modified HPAM for displacement of residual oil

Abstract

Herein, a novel water-soluble comb-shaped polyzwitterion (PNMASt) was prepared by introducing N-maleoyl chitosan, 2-(dimethyl(5-methyl-4-oxohex-5-en-1-yl)ammonio)ethyl sulfite, and other hydrophilic hydrophobic monomers into HPAM via free-radical copolymerization. Chemical structure determination and heat endurance analysis were accomplished via XRD, FTIR and ¹H-NMR spectroscopy, SEM, and TGA. A simulated reservoir environment (shear rates, temperature, and salinity) was used to survey the solution performance and the rheology of the polyzwitterion as a function of the apparent viscosity and changing conditions. PNMASt exhibited excellent thickening efficiency, surface activity, anti-shear behavior, restorable action after shearing, heat tolerance, ageing tolerance, viscoelasticity, and salt tolerance as compared to HPAM under the same simulation environment. Furthermore, a core flooding experiment showed the remarkable flow control capability (R_f = 18.23 and RRf = 6.62), excellent oil production enhancement (13.32%), and remarkable residual oil displacement capacity (6.11%) of PNMASt as compared to those of HPAM.