Improved Methods for Water Shutoff – 1998

R.S. Seright – 1998

Abstract

Final report of the three-year water shutoff project. A predictive model is developed for areal gel front profiles in naturally fractured injection wells, incorporating yield-stress and gel dehydration. In fractures with effective widths of 0.006 to 0.04 inches, Cr(III)-acetate-HPAM gel is concentrated 20 to 40 times during extrusion, delaying propagation by the same factor. A minimum pressure gradient (yield stress) is required to extrude gel through fractures; a correlation is developed for this. No significant gel washout occurs after placement in fractures up to 0.4 inches wide during subsequent brine injection. A systematic philosophy for diagnosing water production problems is proposed, emphasizing root-cause identification before treatment design.

Key Takeaways

  • A model predicts areal gel front profiles in naturally fractured reservoirs — the shape depends primarily on the ratio of on-trend to off-trend fracture conductivity.
  • In fractures 0.006 to 0.04 inches wide, Cr(III)-acetate-HPAM gel is concentrated 20 to 40 times during extrusion, delaying propagation by the same factor — a critical treatment sizing parameter.
  • A minimum pressure gradient (yield stress) is required for gel extrusion through a fracture; for pressure gradients below 1 psi/ft, fracture width should be at least 0.1 inches.
  • No significant gel washout was observed during brine injection after gel placement in fractures up to 0.4 inches wide — confirming good post-placement durability.
  • A systematic philosophy for diagnosing water production problems emphasizes root-cause identification (channeling vs. coning vs. behind-pipe flow) before committing to a treatment approach.
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