A Comparison of Different Types of Blocking Agents

R.S. Seright and J. Liang – 1995

Abstract

Many different materials have been proposed to reduce channeling of fluids through fractures and high-permeability streaks, including gels, particulates, precipitates, microorganisms, foams, and emulsions. This paper compares their placement and permeability reduction properties. Comparisons focus on selectivity in entering high-permeability rock preferentially over low-permeability rock, and ability to reduce permeability more in high-permeability water-saturated zones than in low-permeability oil-saturated zones. Concepts are identified that may lead to blocking agents with placement or permeability-reduction properties superior to those of conventional gels

Key Takeaways

  • Six categories of blocking agents were systematically compared: gels, particulates, precipitates, microorganisms, foams, and emulsions — providing a comprehensive comparative framework for conformance improvement treatment selection.
  • The two critical properties for a blocking agent are: (1) selectivity in entering high-permeability rock over low-permeability rock during placement, and (2) ability to reduce permeability more in high-permeability water-saturated zones than in low-permeability oil-saturated zones after placement.
  • An ideal blocking agent would provide high selectivity on both criteria simultaneously — but existing agents face fundamental tradeoffs between placement selectivity and post-placement permeability reduction selectivity.
  • Concepts are identified that could lead to blocking agents with properties superior to conventional gels — pointing toward design features (controlled particle size, triggerable gelation, capillary-pressure-responsive mobility) that could improve both placement and permeability-reduction selectivity.
  • The systematic comparison framework provides a screening tool for selecting the most appropriate blocking agent for a given reservoir and channeling problem, based on the specific selectivity requirements of the application.
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