Differences in molecular configuration and seepage properties among polymer, active polymer and Cr3+ polymer gel

Key words:  oil displacement agent  molecular configuration  molecular coil dimension  rheological property  seepage property  mechanism analysis

Abstract:

The differences in molecular configuration, molecular coil dimension, as well as rheological and seepage properties among polymer, active polymer, and Cr³⁺ polymer gel were investigated by scanning electron microscopy (SEM), dynamic light scattering (DLS), rheometer and core flow experiment. The results show that a kind of stereoscopic random reticulation is formed when polymer molecules are dissolved in the water solution. The molecular structure of active polymer presents a flake-network configuration. For polymer gel 1 molecules, intra-molecular cross-linking is dominant with subsidiary inter-molecular cross-linking. However, for polymer gel 2 molecules, inter-molecular cross-linking is dominant with subsidiary intra-molecular cross-linking. At the same concentration, the molecular coil dimension (D_h) of active polymer is the largest, followed by polymer gel 2, then the polymer. And the D_h of polymer gel 1 is the smallest. The D_h distribution of active polymer is the most decentralized, followed by polymer gel 1, then the polymer gel 2. And the D_h distribution of polymer is the most centralized. Four oil displacement agents exhibit the rheological property of shear-thickening and followed by shear-thinning, in which the shear-thickening and the shear-thinning of active polymer are most significant. The migration capacity of polymer solution in the porous media is the greatest, followed by polymer gel 1, then polymer gel 2. And the active polymer is the worst. The residual resistance factor of polymer gel is bigger than the resistance factor, showing a kind of peculiar seepage characteristics.