An Alternative View of Filter-Cake Formation in Fractures Inspired by Cr(lll)-Acetate-HPAM Gel Extrusion

R.S. Seright – 2003

Abstract

A new model was developed to describe water leakoff from formed Cr(III)-acetate-HPAM gels during extrusion through fractures. This model is fundamentally different from the conventional filter-cake model used in hydraulic fracturing. The new model correctly predicted the occurrence of wormholes and stable pressure gradients during gel extrusion through fractures — phenomena the conventional model cannot explain. The same new model also accurately predicted leakoff during extrusion of a guar-borate gel used in hydraulic fracturing. The model was validated across a range of fracture conditions, temperatures, gel compositions, and brine injection scenarios after gel placement.

Key Takeaways

  • The conventional filter-cake model from hydraulic fracturing fails to describe water leakoff from polymer gel during fracture extrusion — it cannot predict wormholes or stable pressure gradients observed experimentally.
  • Seright’s new leakoff model, developed from gel extrusion experiments, correctly predicts wormhole formation and stable pressure gradients during Cr(III)-HPAM gel extrusion through fractures.
  • The new model also accurately predicts leakoff during guar-borate gel extrusion — suggesting it may be more broadly applicable to hydraulic fracturing applications than the conventional filter-cake model.
  • Water leakoff from gel is controlled by the gel and fracture properties, with temperature and gel composition also affecting the leakoff behavior — all of these are captured in the new model.
  • Gel behavior in fractures under brine injection after placement was also investigated, providing design data for the post-placement phase of gel conformance treatments.
Read Article

Related Articles