In this study,a PAM-AMPS/Fe3 O4 nano drag reducing agent was synthesized by grafting acrylamide/2-acrylamido-2-methylpropane sulfonic acid(AM/AMPS)copolymer onto nano Fe3O4,the shear dilution of PAM-AMPS/Fe3O4 drag reducing agent was studied by dynamic rheometer,and the influence law of nano-Fe3O4,salt content and shearing action on their rheological behavior was also analyzed.The results show that the particle size of PAM-AMPS/Fe3O4 nano drag reducing agent is 100-500 nm,and the viscosity-average molecular weight is 4.99 X 106 g/mol.At 30 ℃,PAM-AMPS/Fe3 O4 drag reducing agent exhibits significant shear dilution characteristics when the shear rate is greater than 0.3 s-1.The drag reducing agent has a more complex microstructure,and its supercritical mass fraction is 0.035％.Compared with the blank polymer,it shows better viscosity enhancing ability and viscoelasticity behavior.As AMPS contains temperature and salt-tolerant groups,when the mass fraction of NaCl and CaCl2 is 10％and 5％,the viscosity retention rates of PAM-AMPS/Fe3O4 drag reducing agent can reach 69％and 53％respectively,showing a strong salt tolerance.Meanwhile,the viscosity recovery rates of the drag reducing agent after shearing for 3600 s and 7200 s at a shear rate of 1000 s-1 can reach 100％and 94％,respectively,demonstrating a good shear resistance.
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