New Insights Into Polymer Rheology in Porous Media

R.S. Seright, Tianguang Fan, Kathryn Wavrik, Rosangela de Carvalho Balaban – 2011

Abstract

This paper clarifies the rheology of xanthan and HPAM solutions in porous media, especially at low velocities. Previous literature reported resistance factors and apparent shear thinning at low fluxes noticeably greater than expected from viscosity measurements. The polymer component causing this behavior propagates slowly and generally will not penetrate deep into a formation. Particularly for HPAM solutions, this anomalous low-flux shear thinning can be reduced or eliminated by mechanical degradation or flow through a few feet of porous rock. Under practical EOR conditions, HPAM shear thinning is slight or nonexistent at the low velocities relevant to displacement deeper in the reservoir, while shear thickening at high velocities (near the wellbore) remains the dominant rheological phenomenon.

Key Takeaways

  • Anomalously high resistance factors and apparent shear thinning reported in previous literature at low fluxes are caused by a slowly propagating polymer component — not representative of bulk polymer rheology deep in the reservoir.
  • This slowly propagating, high-resistance-factor component does not penetrate deep into the formation — once it is displaced by subsequent flow, HPAM behavior at low fluxes approaches Newtonian, consistent with viscometer measurements.
  • Mechanical degradation or flow through a few feet of porous rock effectively eliminates the anomalous low-flux shear-thinning behavior — both of which routinely occur near the wellbore during polymer injection.
  • Under practical EOR conditions relevant to deep reservoir flow (low velocities), HPAM shear thinning is slight or nonexistent — shear thickening at high velocities near the wellbore is the dominant rheological consideration.
  • The paper reconciles conflicting previous literature on low-flux HPAM and xanthan rheology by identifying the slowly propagating high-resistance component as the source of the discrepancy — clarifying the correct input for polymer flood simulation.
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