Improved Techniques for Fluid Diversion in Oil Recovery – 1993

R.S. Seright – 1993

Abstract

First year of a new three-year project comparing gels with foams, emulsions, and particulates for fluid diversion, and identifying mechanisms of selective water permeability reduction. A survey of 1980-1992 field data and expert interviews at eight major oil companies establishes candidate selection criteria for injection and production wells. Theoretical analysis shows viscous forces dominate gravity during gelant injection into fractured wells. Preformed gels dramatically outperform in-situ-forming gelants at healing fractures and improving sweep. DPR is insensitive to core orientation, oil viscosity (1 to 31 cp), and system pressure (0 to 1500 psi). Two strategies to minimize fracture leakoff are identified: (1) time gelation before fracture entry, and (2) add particulates to the gelant.

Key Takeaways

  • Comprehensive 1980-1992 field data survey and expert interviews at eight major oil companies establish practical candidate selection criteria for both injection well and production well gel treatments.
  • Preformed gels improve sweep efficiency in fractured cores far more effectively than in-situ-forming gelants — a decisive experimental advantage for fractured reservoir applications.
  • DPR is insensitive to core orientation, oil viscosity (1 to 31 cp), and system pressure (0 to 1500 psi) — confirming it is a robust property applicable across a wide range of reservoir conditions.
  • Two strategies to minimize gelant leakoff in fractured systems: design gelation timing so gel forms before leaving the wellbore, or add gelled material/particulates to the gelant.
  • Viscous forces dominate over gravity during gelant injection into fractured wells; however, after shut-in, rapid interface equilibration can be exploited in oil wells with fractured water cones.
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