Investigation of Polymer Slug Viscosity in Porous Media

In order to maintain reservoir pressure and also to sweep out oil efficiently, water
flooding became the standard practice in many reservoir formations. The efficiency of
the water flood oil displacement mechanism as a result of an unfavorable mobility ratio
was identified. Polymer solutions are designed to develop a favorable mobility ratio
between injected polymer solution and the oil or water bank being displaced a head of
the polymer. The purpose is to develop a more uniform volumetric sweep of the
reservoir, both vertically and aerially. An experimental study has been conducted to
examine the effects of a dilute aqueous solutions of a partially hydrolyzed
polyacrylamide polymer, over a wide range of parameters. In general, the viscosityshear
rate relationship was found to obey the Newtonian behavior at low shear rates and
a power-law behavior at high shear rates with the power indices from 0.2 to 0.6.
However, adding an ionic species such as sodium chloride (NaCl), reduced the
hydrodynamic size of the polymer molecule (physical change), changing the viscosityshear
rate relationship. The viscosity-shear rate relationship was found to be a strong
function of cation type only at salt concentrations less than 2 wt%. The viscosity values
showed that polymer solutions are more affected by the different molecular weight of
polymer than the degree of hydrolysis used. The higher concentration of polymer will
make the polymer solution viscosity increasing. The different pressure applied on the
polymer solution will effect on the viscosity at the certain range. This study
demonstrates the effect of several parameters to the polymer solution viscosity that
significantly influencing the performance of chemical flooding in EOR.