Conformance Control Using Gels – 2002

R.S. Seright – 2002

Abstract

First year of a new conformance improvement project. Gel extrusion and washout are characterized: in narrow fractures (1 mm or less), washout pressure gradient equals placement pressure gradient; in wider fractures (greater than 2 mm), washout can occur at significantly lower pressure gradients. A secondary gelation concept — gel crosslinks twice, first before fracture entry and then after placement — shows considerable promise. Gels in fractures (not just porous rock) can provide significant DPR. Casing pinhole leak plugging with Cr(III)-acetate-HPAM gel is demonstrated to be feasible at pressure gradients up to 3000 psi/ft. AquaCon adsorption-based polymer shows high variability in DPR performance.

Key Takeaways

  • In fractures 1 mm wide or narrower, gel washout pressure gradient equals placement pressure gradient — gel is as hard to remove as it was to place. In fractures wider than 2 mm, gel washout can occur at much lower pressure gradients.
  • A secondary gelation concept — gel crosslinks twice, blocking matrix invasion before entry and then strengthening after placement — shows considerable promise for wide-fracture washout prevention.
  • Gels residing in fractures (not just in porous rock) can provide significant DPR — an unexpected finding opening new design possibilities for fracture-dominated production well treatments.
  • A 5 percent HPAM Cr(III)-acetate gel can plug casing pinhole leaks, reducing permeability to 1 to 2 microdarcy and withstanding pressure gradients up to 3000 psi/ft in porous rock.
  • AquaCon adsorption-based polymer shows high variability in DPR performance — unpredictable for field applications compared to strong pore-filling gel systems.
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