One of the most important factors in chemical enhanced oil recovery (EOR) is mobility control, for which partially hydrolyzed polyacrylamide (HPAM) and other polymers are extensively used. An accurate description of the polymer viscosity is needed to simulate field performance accurately. Rheological properties of the EOR polymer solutions depend on the polymer's molecular properties and concentration, salinity, shear rate and temperature.. Rheological measurements with commonly employed EOR polymers were made and the parameters in the rheological models that correlate polymer viscosity with these variables were determined and used to develop a polymer database.
The rheological measurements have been made to characterize the apparent viscosity of EOR polymers (mainly HPAM polymers) as a function of shear rate, polymer concentration, polymer molecular weight, degree of hydrolysis, salinity, hardness, and temperature. In addition to the steady shear viscosities, the oscillatory rheological properties have also been measured to better define the polymer behavior during flow in reservoir rocks. In view of the recent EOR applications to recover viscous oils and to offshore fields, the data were obtained for wider ranges of the polymer molecular weight and concentration, and salinity, than those reported in the literature. A comprehensive compilation of the rheological data and polymer parameters for currently available EOR polymers was needed since these polymers often have different properties than similar polymers that were studied during the earlier period of active chemical EOR research 20 to 30 years ago.