Flow characteristics of polymer solutions and crosslinked gels through porous media form the bases for several important enhanced oil recovery processes. When a polymer solution is injected into a reservoir for mobility control, flow distribution determines the flood efficiency. When Cr(III) crosslinking is applied to xanthan for profile modification, flow distribution of the gel solution along with gelation kinetics dictates gel placement and its effectiveness in improving subsequent water flooding.
Rheological characteristics of xanthan and xanthan/Cr(III) solutions are discussed in this paper. Flow rate ratios between capillary bundles of contrasting permeabilities were measured. Flow rate ratios of shear-thinning xanthan and xanthan/Cr(III) solutions were shown to be higher than those of water at low shear rates. Thus, biopolymer solutions are expected to preferentially enter high-permeability streaks in a reservoir formation. A theory to explain this selective emplacement characteristic has been formulated by combining a rheological model and Darcy’s law.