| Characteristics of viscous fingering patterns in miscible displacements of non-Newtonian polymer solutions and Newtonian glycerol solutions were experimentally investigated in a rectangular Hele-Shaw cell. Alcoflood™ polymers of three different molecular weights were used to make nine test solutions with different concentrations. The results of rheological characterization for the polymer solutions show that higher molecular weight polymers displayed stronger shear thinning behavior and higher zero-shear viscosity at same concentration. The effects of molecular weight, mobility ratio, and injection rate on fingering morphology, finger tip velocity, and relative finger width were investigated.; Compared to the Newtonian displacements, the miscible displacements of polymer solutions exhibited more complex fingering phenomena, such as tip-thinning, dense-branching, multiple dense-branching and skewering. The experiments show that the power-law index, n, appears to significantly affect fingering morphology and the relative finger width.; The experimental results were also compared with the predicted results by a numerical simulator, which uses the Carreau-Yasuda model to deal with the shear-thinning behavior of polymer solutions. The predicted value of the average finger tip velocity and relative finger width were all in good agreement with our experiments, even though some of the fingering phenomena observed in the experiments were absent in the simulation results. |
