Flow characteristic of polymer solutions in porous media: Influence of the molecular weight and concentration

Abstract

The polymer solution flow in porous media is a central research topic related to hydraulic fracturing measures, formation damage and fracture propagation. Influenced by molecular weights and concentrations, various flow patterns of polymer in pores are presented, resulting in different filtration loss. In this work, the effectiveness of various polymer solutions for filtration loss was assessed by utilizing the core flooding experiment firstly. The result shows that lesser filtration loss normally is inextricably linked to solutions with high molecular weight and concentration. Subsequently, the flow behaviors of polymer solutions investigated by designed micro pore-throat structure and micro-particle image velocimetry (μ-PIV) further confirmed the above result. It was found that the central convergent flow pattern benefiting from higher viscous force loss and less filtration loss was observed at high flow rates (0.5 mL/h), and higher molecular weight and concentration were more prone to convergent flow patterns. The viscosity force loss increases by about 4 times varying the molecular weight of polymer from 5 × 10⁶ to 18 × 10⁶ g/mol or the concentration from 0.05 to 0.3%. It interprets higher molecular weight and concentration in core studies and field observations with decreased filtration loss of HPAM. This work provides a theoretical foundation for the application of fracturing fluids as well as fresh perspectives on how to access the filtration loss of fracturing fluids.