ABSTRACT Oilfield polymers such as HEC (Hydroxyethyl Cellulose) and Xanvis™ (Xanthan Gum) solutions are filtered to remove microgels and minimize formation plugging. Mechanical and hydraulic shearing of the gel alter the rheology of the polymers. Field data on various concentrations of HEC and Xanvis show the effects of each shearing mechanism on polymer viscosity, sand fall rate, and leakoff. A guideline for the on-site evaluation of the quality of sheared and filtered HEC is presented so that excessive shearing and unnecessary degradation of the gel can be recognized and prevented.