Improved Methods for Water Shutoff – 1996

R.S. Seright – 2006

Abstract

First year of a new three-year project on improved water shutoff methods. A comprehensive review of gel placement concepts in both linear and radial flow systems establishes that acceptable gel placement is far easier in linear flow (fractures) than in radial flow (unfractured wells). In radial flow systems, zone isolation during gelant placement is essentially mandatory to protect oil-productive zones. Gel properties in fractures are characterized for Cr(III)-acetate-HPAM gels. Preformed gels are shown to have a placement advantage over water-like gelants for fracture length ratios below 3. Gel aging significantly increases fracture resistance factors during the first 24 hours. DPR mechanism studies continue. Project supported by DOE, BDM-Oklahoma, and 15 oil companies.

Key Takeaways

  • Acceptable gelant placement is far easier in linear flow (fractures, flow behind pipe) than in radial flow (unfractured wells) — the Darcy equation shows gelants penetrate all open zones in both regimes.
  • Zone isolation is essentially mandatory during gelant placement in unfractured (radial flow) wells to protect oil-productive zones — no reliable selective placement mechanism exists for radial flow.
  • Gel dehydration during fracture extrusion aids placement selectivity; preformed gels have a placement advantage over water-like gelants for fracture length ratios below 3.
  • Gel resistance factors in fractures increase rapidly during the first 24 hours of aging, then more gradually — aging time must be controlled in field applications.
  • Diffusion and dispersion cannot be exploited for selective gel placement in injection wells, even under extreme heterogeneity — zone isolation remains the only reliable approach.
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