Abstract
This paper clarifies the rheology of xanthan and HPAM solutions in porous media, especially at low velocities. Previous literature reported resistance factors (effective viscosities in porous media) and an apparent shear thinning at low fluxes that were noticeably greater than expected from viscosity measurements. The polymer component that causes the latter behavior is shown to propagate quite slowly and generally will not penetrate deep in a formation. Particularly for HPAM solutions, this behavior can be reduced or eliminated for solutions that experience mechanical degradation and/or flow through a few feet of porous rock. Under practical conditions where HPAM is used for enhanced oil recovery, the degree of shear thinning is slight or non-existent, especially compared to the level of shear thickening that occurs at high fluxes.
