Effect of Rheology on Gel Placement

R.S. Seright – 1991

Abstract

This study investigates whether the non-Newtonian rheology of gelling agents can be exploited to eliminate the need for zone isolation during gel placement in injection wells. Eight different rheological models were applied to represent the properties of existing non-Newtonian gelling agents. Gel placement was examined in linear and radial parallel corefloods and in fractured and unfractured injection wells. The analysis indicates that, compared with water-like gelling agents, existing non-Newtonian gelling agents will not reduce the need for zone isolation during gel placement in radial-flow systems (unfractured wells). This finding has important implications for field gel treatment design.

Key Takeaways

  • Non-Newtonian rheology of existing gelling agents does not eliminate the need for zone isolation during gel placement in radial-flow (unfractured) injection wells — this conclusion holds across eight different rheological models.
  • Compared with water-like (Newtonian) gelling agents, non-Newtonian gelling agents do not provide meaningfully better selective entry into high-permeability zones in radial-flow systems — the hoped-for selectivity does not materialize.
  • Zone isolation remains the primary mechanism for protecting oil-productive zones from gelant invasion during gel treatment in unfractured injection wells — rheology engineering alone cannot substitute for mechanical isolation.
  • The analysis spans linear and radial corefloods as well as fractured and unfractured injection wells, showing that fractured wells are more tolerant of non-isolated gel placement than unfractured wells.
  • Field practitioners who rely on non-Newtonian rheology to provide selective placement in unfractured wells are likely overestimating the degree of protection the rheology provides — zone isolation should not be abandoned based on rheology considerations alone.
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