Dynamic gelation of the HPAM/phenol–formaldehyde resin gel under oscillatory shear: critical gelation shear rate and reformation

Polymer gel is widely used in oilfield development and has achieved remarkable results in water shutoff and conference control. To comprehensively understand the dynamic gelation of polymer gel, the dynamic gelation of phenol–formaldehyde resin gel is studied under oscillatory shear, which is described by the change in viscosity with shear time. The kinetic formula of the crosslinking reaction of polymer gel under oscillatory shear is fitted by the quantitative relationship between the gelation time and gel strength of dynamic and static gelation. The definition of the critical gelation shear rate is proposed, and that of polymer gel under oscillatory shear is determined. The critical gelation shear rate increases with the increasing mass concentration of the polymer and crosslinker. The viscosity of the process of static gelation after oscillatory shear is analyzed to characterize gel reformation. The shear may have little effect on the viscosity of the static gelation after oscillatory shear in the induction stage but could make the viscosity rapidly decrease in the gelation stage. Viscoelastic experiments show that the phenol–formaldehyde resin gel has a good reformation ability after shear only when the shear rate is less than the critical gelation shear rate. The results provide a theoretical basis for the selection of the appropriate shear rate and shear time in the field application of polymer gel.