An empirical investigation of polymer flow in porous media

Steady-state flow experimental data have been analyzed for two commonly use d polymers representing two generic classes, polysaccharides (Xanflood), an d partially hydrolyzed polyacrylamides (Pusher-700), flowing inside bead pa cks and Berea sandstone. Oscillatory flow measurements have been used to co mpute the polymer solution's longest relaxation time (theta(f1)), which is referred to as the characteristic relaxation time in this paper. Steady-sta te flow experimental data for the two polymers combined with measured polym er viscous properties have been converted to average shear stress-shear rat e data inside porous media. An average power-law exponent ((n) over bar) is therefore obtained for the polymer flow inside the porous medium. Using th eta(f1), (n) over bar, rock perneability (k), porosity (phi), and fluid flo w velocity (u), a viscoelasticity number (N-v) is calculated and found to s trongly correlate with the pressure gradient inside porous media. This corr elation is the basis for defining a viscoelastic model for polymer flow, an alogous to Darcy's law. The proposed model asserts a nonlinear relationship between fluid velocity and pressure gradient. It accounts for polymer elas ticity and for pore geometry changes due to molecular adsorption and mechan ical entrapment.