New Insight Into Wormhole Formation in Polymer Gel During Water Chase Floods With Positron Emission Tomography

B. Brattekås, M. Steinsbø, A. Graue, M. A. Fernø, H. Espedal, R. S. Seright – 2017

Abstract

PET (positron emission tomography) and CT (computed tomography) imaging were combined to quantify Cr(III)-acetate-HPAM gel behavior during chase waterflooding in fractured core plugs. Gel was placed in cores with longitudinal fractures, and F-18 labeled water was injected during chase floods to visualize and quantify local flows with PET. The study directly visualized gel rupture and wormhole development as a function of flow rate, providing spatial confirmation of gel behavior models previously inferred from pressure measurements and material balance alone. PET imaging revealed local flow redistribution during gel erosion that cannot be extracted from global measurements.

Key Takeaways

  • PET/CT imaging directly visualizes wormhole formation and development during gel erosion in fractures — providing spatial confirmation of the wormhole-flow model previously inferred only from pressure measurements and effluent analysis.
  • F-18 labeled water injected during chase floods enables local flow quantification within gel-filled fractures, revealing flow redistribution during gel rupture that is invisible in global pressure and production measurements.
  • Wormhole development during gel erosion follows a rate-dependent pattern — the flow rate of the chase flood controls how wormholes initiate, grow, and affect the blocking capacity of the gel over time.
  • PET imaging enables direct comparison of local flow patterns to global measurements (differential pressure and production rate), allowing verification that existing gel-behavior models correctly describe the internal gel structure.
  • The complementary PET/CT approach provides information about local fluid saturations and dynamic spatial flow within both the fracture and gel network — a capability not available from any previous experimental method for studying gel in fractures.
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