A REVIEW OF GEL PLACEMENT CONCEPTS
Table of contents
 
  1. Linear Versus Radial Flow

  2. In Unfractured Wells (Radial Flow), Is Protection of Oil Zones Needed During Gelant Placement in Heterogeneous Reservoirs? (Yes.)

  3. Are Field Results Consistent with Calculations Using the Darcy Equation? (Yes.)

  4. Do Hall Plots Indicate Selectivity During Gelant Placement? (No.)

  5. Is Gel Placement Important in Wells or Reservoirs with Fractures? (Yes.)

  6. Can Relative-Permeability Effects Be Exploited to Prevent Gelants from Entering Oil Zones? (No.)

  7. Can Capillary-Pressure Effects Be Exploited to Prevent Water-Based Gelants from Entering Oil Zones? (In field applications—no. In oil-wet laboratory cores—sometimes.)

  8. Since Some Polymers and Gels Can Reduce kw Much More than ko or kg, Where Will This Property Be Most Useful? (Wells and reservoirs where vertical fractures cut through both water and hydrocarbon zones.)

  9. Can Gel Treatments Effectively Mitigate Three-Dimensional Coning? (No, except in rare circumstances.)

  10. Can Gel Treatments Effectively Mitigate "Two-Dimensional Coning" in Fractured Wells? (Yes, with the proper gel placement and gel properties.)

  11. In Radial-Flow Systems, Can the Rheology of Existing Non-Newtonian Polymer Solutions Provide a Better Placement than That for Gelants with Water-Like Viscosities? (No.)

  12. Are Gel Treatments Fundamentally Different from Polymer Floods? (Yes.)

  13. Since Chemical Propagation and Retention Rates Vary with Permeability, Can These Differences Be Exploited to Eliminate the Need to Protect Hydrocarbon-Productive Zones During Gelant Placement? (No, based on evidence to date. However, this may be possible in the future, depending on research progress.)

  14. Can Diffusion Be Exploited to Dilute the Gelant Bank in Low-Permeability Zones Enough to Prevent Gelation, While Allowing an Effective Gel Plug to Form in High-Permeability Zones? (Only if the gelant banks are extremely small-- < 1 ft.)

  15. Can Dispersion Be Exploited to Dilute the Gelant Bank in Low-Permeability Zones Enough to Prevent Gelation, While Allowing an Effective Gel Plug to Form in High-Permeability Zones? (No.)

  16. In Systems Without the Potential for Crossflow, Can a More Selective Gel Placement Be Achieved by Injecting a Water-Like Gelant Followed by a Water Postflush? (No.)

  17. When Using Viscous Gelants, Can Viscous Fingering by a Water Postflush Reliably Breakthrough the Gelant Bank in Low-Permeability Zones Before That in High-Permeability Zones? (No.)

  18. Can Worm-Holing by a Degrading Postflush Reliably Breakthrough the Gel Bank in Low-Permeability Zones Before That in High-Permeability Zones? (No.) 20

  19. In Systems with the Potential for Crossflow, Can a More Selective Gel Placement Be Achieved by Injecting a Gelant Followed by a Mobility-Matched Postflush? (Yes, under limited circumstances.)

  20. Can Pressure-Transient Effects Be Exploited to Minimize Gelant Penetration into Low-Permeability Zones? (Yes, under limited circumstances, and only if intra-wellbore crossflow is confirmed to occur for a sufficiently long period of time.)

  21. Can Anisotropic Permeability or Pressure Distributions Around an Unfractured Well Be Exploited to Eliminate the Need to Protect Hydrocarbon-Productive Zones During Gelant Placement? (No.)

  22. Can Gravity and Fluid Density Differences Be Exploited to Optimize Gelant Placement? (Yes, for some cases in fractured wells. Usually, no, for unfractured wells.)

  23. Can Suspensions of Particles (Including Gel Particles) Show Better Placement Properties than Gelants When Used as Blocking Agents? (No, except under rare circumstances.)

  24. Can Precipitates and Other Products of Phase Transitions Show Better Placement Properties than Gelants When Used as Blocking Agents? (No.)

  25. Can Microorganisms Show Better Placement Properties than Gelants When Used as Blocking Agents? (No, except under rare circumstances.)

  26. Can Foams Show Better Placement Properties than Gelants When Used as Blocking Agents? (Yes, under limited circumstances.)

  27. Can Emulsions Show Better Placement Properties than Gelants When Used as Blocking Agents? (No.)

  28. Other Special Situations and Methods.

  29. Conclusions

  30. Nomenclature

  31. Acknowledgments

  32. References