Fracturing Fluid High-Temperature Breaker for Improving Well Performance

Abstract

E&P Exchange Crosslinked polymers (borate and organo-metallic) are used routinely in fracturing treatments. At temperatures exceeding 225°F, thermal oxidation has been considered sufficient for degradation of the crosslinked polymer. However, industry consortium studies have shown that damage caused by the polymeric gels at high temperatures can be significant. These studies did not use oxidative breakers to remove damage, which indicates that thermal degradation of polymeric gels is slow and incomplete without the aid of oxidation, even at high temperatures. Gel breakers, oxidative and enzymatic, are used to degrade the polymer and to clean up the proppant pack. The most commonly used oxidative breakers (persulfate salts) and enzymes are limited by temperature (200°F) and/or pH (3 to 9). The reactivity of the oxidative breakers increases with temperature and limits the amount of breaker that can be used for degradation of the polymer gel without premature loss of viscosity. High concentrations of oxidative breakers have been shown to improve proppant-pack permeability significantly. The reactivity of the oxidative breakers can be delayed by encapsulation, which allows increased concentrations within the proppant pack for polymeric gel/filter-cake removal. Field and laboratory studies have shown the benefits of delayed release breakers for gel/filter-cake removal. The delayed breaker improved fracture conductivity and well performance. Encapsulation of persulfate breakers can extend their temperature range but may have little effect on polymeric damage reduction at temperatures exceeding 225°F.