Rheology of a New Sulfonic Associative Polymer in Porous Media

R.S. Seright, Tianguang Fan, Kathryn Wavrik, Hao Wan, Nicolas Gaillard, Cédrick Favéro – 2011

Abstract

This paper investigates the porous-media behavior of a new hydrophobically associative tetra-polymer with low hydrophobic-monomer content, Mw of 12–17 million g/mol, and 15–25 mol% total anionic content including a few percent of a sulfonic monomer. The associative polymer is compared with a conventional HPAM of 18–20 million g/mol and 35–40% anionic content. Bulk rheological properties were similar for both polymers. In cores from 300 to 13,000 md, neither polymer caused face plugging. The associative polymer provided low-flux resistance factors two to three times those expected from viscosity alone — an effect not eliminated by moderate shear degradation or flow through a few feet of rock. Propagation experiments in cores up to 157 cm suggest these high resistance factors could propagate deep into the reservoir. The associative polymer shows significantly higher shear thinning at low fluxes and lower shear thickening at high fluxes compared to conventional HPAM.

Key Takeaways

  • A new sulfonic associative polymer (tetra-polymer, Mw 12–17 million g/mol, 15–25 mol% anionic content) provides low-flux resistance factors in porous media two to three times greater than expected from its viscosity alone — substantially exceeding the performance of a conventional HPAM with similar bulk rheology.
  • Unlike conventional HPAM, the enhanced low-flux resistance factors of the associative polymer are not eliminated by moderate shear degradation or flow through a few feet of porous rock — suggesting the hydrophobic associations are re-formed after degradation.
  • Propagation experiments in long cores up to 157 cm indicate the high resistance factors propagate deep into the reservoir — not just a near-wellbore phenomenon — providing potentially enhanced sweep efficiency over conventional HPAM.
  • The associative polymer shows significantly higher shear thinning at low velocities and lower shear thickening at high velocities compared to conventional HPAM — a favorable profile that reduces near-wellbore injectivity loss while delivering enhanced displacement efficiency deeper in the reservoir.
  • Neither the associative polymer nor the conventional HPAM caused face plugging or internal filter cake formation in cores from 300 to 13,000 md, confirming acceptable injectivity for high-permeability reservoir applications.
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