Effect of Fe²⁺ on the apparent viscosity of polymer solution and controlling methods

The influences of Fe²⁺ on the apparent viscosity of polymer solution have been studied in this paper, and the results showed that a small amount of Fe²⁺ would make the polymer degraded severely. HPAM polymer molecular weight and viscosity declined dramatically with the increasing of C_Fe²⁺ among the 0~0.5 mg/L, and declined slowly when the C_Fe²⁺ above a concentration of 0.5mg/L. The AFM photos also showed that polymer network structure was destroyed largely. In order to ensure the polymer viscosity, the contents of Fe²⁺ in preparation water should not exceed to the concentration of 0.5 mg/L. There are several controlling measures used to remove Fe²⁺ in preparation water, such as oxygen exposure, chemical complex method and manganese sand filtration. Chemical complex method is the most simple and effective one among them. The high effective iron removal reagent BHCT-1 with a concentration of 300 mg/L showed a good effect to remove Fe²⁺. For example, it was applied in offshore polymer flooding oilfield, and the viscosity of polymer solution would be increased by more than 20%.