Further Investigations of Why Gels Reduce Water Permeability More Than Oil Permeability

Jenn-Tai Liang; R.S. Seright – 1997

Abstract

This paper examines multiple possible explanations for why gels reduce water permeability more than oil permeability. Experiments show the effect is not caused by gravity, lubrication effects, gel shrinking/swelling, or wettability differences as root causes. Results from an oil-based gel experiment suggest that microscopic segregation of oil and water pathways through the porous medium may play the dominant role — water-based gels preferentially block water pathways while leaving oil pathways relatively unobstructed. The study does not definitively prove this mechanism but identifies microscale pathway segregation as the most promising hypothesis for subsequent investigation.

Key Takeaways

  • Gravity effects do not explain DPR — the phenomenon occurs consistently independent of core orientation, ruling out buoyancy-driven phase separation as a cause.
  • Lubrication effects (water films lubricating gel movement) do not explain the magnitude of DPR observed — the effect is too large and too consistent to arise from lubrication alone.
  • Gel shrinking and swelling in response to oil vs. water contact does not appear to be the primary driver — the timescale and magnitude of shrinkage/swelling are inconsistent with the observed permeability behavior.
  • Wettability may play a supporting role in DPR but does not appear to be the root cause — the phenomenon is observed in both water-wet and oil-wet porous media.
  • Microscale segregation of oil and water pathways through porous media — where water-based gels preferentially follow and occupy water pathways — is identified as the most promising mechanistic explanation, validated by experiments with an oil-based gel.
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