Hyper-branched structure—an active carrier for copolymer with surface activity, anti-polyelectrolyte effect and hydrophobic association in enhanced oil recovery

Herein, a hyper-branched polymer h-PMAD with, simultaneously, surface activity, an anti-polyelectrolyte effect and a hydrophobic association was prepared via aqueous solution free radical polymerization, and characterized by IR, NMR, TG-DTG and SEM. The polymer h-PMAD provided excellent comprehensive properties in terms of surface activity, thickening, water solubility, rheology andaging, whichwere comparedwith studiesofHPAMand the homologous linear polymer PMAD. Specifically, the IFT value was 55.40 mN m(-1), 789.24 mPa s apparent viscosity with a dissolution time of 72 min, 97.72, 90.77 and 105.81 mPa s with Na+, Ca2+ and Mg2+ of 20 000, 2000 and 2000 mg L-1, respectively. Meanwhile, the non-Newtonian shear thinning behavior had a 96.33% viscosity retention while the shear rate went from 170 s(-1) to 510 s(-1) and then returned to 170 s(-1) again and 0.12 Hz curve, with an intersection frequency of G 0 and G 00. Also, it had 33.51% and 50.96% viscosity retention in formation and deionized water at 100 degrees C and a low viscosity loss in formation water at 80 degrees C over 4 weeks. Moreover, the h-PMAD had an EOR of 11.61%, was obviously higher than PMAD with 8.19% and HPAM with 5.88%. Most importantly, the better EOR of h-PMAD over that of PMAD testified that the hyper-branched structure provided an active carrier for copolymers with functionalized monomers to exert greater effects in displacement systems, which is of an extraordinary meaning.