Water permeability reduction under flow-induced polymer adsorption

The influence of induced polymer adsorption for reducing the effective permeability to water in reservoirs is investigated. Previous studies on polymer adsorption in porous media have shown that a static adsorption regime exists at low shear rates of injection. This results in a thin polymer layer whose capability to reduce water permeability is marginal. However, polymer injection at increasing shear rates has revealed an increase in the adsorbed polymer layer and, consequently, improved water permeability reduction. Here, results from sandpacks are presented to show that at increased shear rates, there is improvement in the adsorbed polymer layer. This phenomenon is known as "flow-induced adsorption." The experiments indicate that above a critical shear rate, there is a shift in the permeability-reduction mechanism from static to flow-induced adsorption, necessitating a sharp increase in the adsorbed polymer layer. All results revealed that the critical shear rate for this polymer is about 300 s(-1) in the absence of mechanical degradation. This critical shear rate defines the optimal rate of polymer injection for better economic viability of the process. The findings of this study improve the current understanding of the mechanisms involved during polymer squeeze operations and therefore will assist in developing better injection processes with improved chances for success.