Regained permeability studies with HEC polymer in high-permeability cores revealed that persulfate-type oxidizing breaker and enzyme breaker do not adequately degrade the polymer. Use of high concentrations of acid or peroxide breakers did show improved breaking, but additional work is needed to apply high concentrations of these breakers properly. Sodium persulfate breaker was found to be thermally decomposed, and its decomposition was accelerated by formation minerals. Enzyme breaker adsorbed onto the formation, but still partly functioned as a breaker. Dynamic fluid-loss tests with reduced-pH, borate-crosslinked gels suggest that accelerated leakoff away from the wellbore could be obtained through the use of a delayed-release acid. Rheological measurements confirmed that a soluble delayed-release acid could be used to convert a borate-crosslinked fluid into a linear gel. This conversion was visually confirmed by tests involving a delayed-release acid and a borate-crosslinked fluid in a single-pass flow loop apparatus. Higher concentrations of breaker were placed in a borate-crosslinked fluid by encapsulating the breaker, and controlled viscosity reduction was obtained.

A simulation using a 3D commercial simulator showed improved cumulative oil production when increased fluid loss from a soluble delayed-release acid was applied.

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