Reduction of Gas and Water Permeabilities Using Gels

R.S. Seright – 1995

Abstract

This paper investigates how different gel types reduce permeability to water and compressed gases (CO₂ and N₂) in porous rock, including a weak resorcinol-formaldehyde gel, a strong resorcinol-formaldehyde gel, a Cr(III)-xanthan gel, a Cr(III)-acetate-HPAM gel, and a colloidal-silica gel. An inline high-pressure spectrophotometer allowed tracer studies without depressurizing. Analogies are noted between gas and water permeability reduction results from a parallel oil study. Results cover permeability reduction characteristics and stability to repeated water-alternating-gas (WAG) cycles at pressures up to 1,500 psi — directly relevant to gel treatments for channeling control in high-pressure gas and CO₂ floods.

Key Takeaways

  • Five gel types were systematically compared for gas and water permeability reduction — weak and strong resorcinol-formaldehyde, Cr(III)-xanthan, Cr(III)-acetate-HPAM, and colloidal silica — providing comparative data for gel selection in gas and WAG flood applications.
  • Gel performance under repeated water-alternating-gas (WAG) cycles at up to 1,500 psi was characterized — critical for applications where gel treatments must withstand multiple cycles of gas and brine injection without losing blocking effectiveness.
  • Strong analogies exist between gas-water permeability reduction results and the parallel oil-water DPR results — suggesting that the same pore-scale mechanisms operate for both oil and gas as the non-aqueous phase.
  • An inline high-pressure spectrophotometer technique was developed to perform tracer studies at up to 1,500 psi without depressurizing the core — a methodological contribution enabling characterization of gel behavior under realistic high-pressure gas flood conditions.
  • Results are directly applicable to gel diversion treatments in CO₂ EOR floods and high-pressure gas floods, where gel must reduce gas channeling while allowing oil to flow through the treated interval.
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