Fluid Diversion and Sweep Improvement with Chemical Gels in Oil Recovery Processes – 1990

R.S. Seright; F.D. Martin – 1990

Abstract

First year of a three-year study on fluid diversion with chemical gels in oil recovery. Objectives: identify gel diversion mechanisms and establish best-use guidelines. Resorcinol-formaldehyde gels at pH 9 achieve very high residual resistance factors (10^3 to 10^4); gelation is inhibited as pH drops below 7. Diffusion and dispersion cannot eliminate zone-isolation requirements in unfractured injection wells. Mathematical analysis shows gelants penetrate all open zones in both injection and production wells. Disproportionate permeability reduction — water permeability reduced more than oil permeability — is identified as critical for production well applications. Preformed gels outperform in-situ-forming gelants at healing fractures and improving sweep.

Key Takeaways

  • Resorcinol-formaldehyde gels buffered at pH 9 achieve residual resistance factors of 10^3 to 10^4; gelation is sharply inhibited below pH 7 — a critical design constraint for carbonate reservoirs.
  • Diffusion and dispersion cannot eliminate zone isolation requirements during gel placement in unfractured injection wells, regardless of reservoir heterogeneity.
  • Gelants penetrate all open zones, not just high-water-saturation zones — zone isolation or careful design is essential to protect oil-productive strata.
  • Disproportionate permeability reduction (DPR) — water permeability blocked much more than oil — is critical for production well treatments where zone isolation is not feasible.
  • Preformed gels improve sweep efficiency in fractured systems by healing fractures far more effectively than in-situ-forming gelants in controlled experiments.
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