Mechanical Degradation of Polyacrylamides Induced by Flow Through Porous Media

R.S. Seright, J.M. Maerker, G. Holzwarth – 1981

Abstract

This early paper describes methods for assessing mechanical degradation of polyacrylamides and investigates the factors influencing degradation during flow through porous media. A technique is described whereby polymer molecular weight distributions are determined from sedimentation velocity measurements using fluorescently labeled polymers in an ultracentrifuge. Molecular weight distributions of native and degraded polymers from three different HPAM products are presented and compared with viscosity, screen factor, and resistance factor assessments of degradation. A simple model for predicting degraded molecular weight distributions is presented based on the assumption that the probability of a molecule breaking in half scales with a characteristic molecular weight parameter. The work demonstrates that molecular weight distribution measurements provide polymer-concentration-independent comparisons among different polymer products — an advantage over viscosity and screen factor measurements which depend on concentration and salinity.

Key Takeaways

  • Fluorescence-labeled sedimentation velocity measurements in an ultracentrifuge directly measure polyacrylamide molecular weight distributions before and after mechanical degradation — providing a polymer-concentration-independent characterization method.
  • Molecular weight distribution measurements enable product comparisons that are independent of concentration, salinity, and polymer source — overcoming key limitations of viscosity and screen factor assessments.
  • A simple model predicts degraded molecular weight distributions by assuming the probability of a molecule breaking in half scales with a characteristic parameter Mp — and the model fits experimental distributions from three different HPAM products well.
  • Screen factors, resistance factors, and viscosities all correlate with degree of mechanical degradation but are concentration- and salinity-dependent — they should be used alongside molecular weight distribution measurements for complete characterization.
  • Different HPAM products from different manufacturers show different inherent resistance to mechanical degradation at the same initial molecular weight — product selection cannot be based on Mw alone.
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