Enzymes are useful breakers in water-based fracturing fluids, but delaying the release of the enzyme provides many advantages. These advantages include delaying the break of the fluid to provide improved fluid rheology, increased breaker concentration improves fracture conductivity and a solid filterable breaker concentrates the added breaker in the fracture. These advantages will lead to better proppant placement and improved production increases.

A study of the interdependence of temperature and pH on enzyme activity was investigated. These results indicated the limitations of enzymes as breakers in fracturing fluids, but the lifetimes of enzymes at higher pH and temperature were longer than expected. Laboratory investigation of improved fluid performance was investigated using delayed static break time, improved viscosity profiles, and filter cake dissolution study. Static break times were significantly longer than normally obtained in typical low temperature fracturing fluids with conventional enzyme breakers. This also resulted in better viscosity profiles especially in early time. Filter cake dissolution studies pointed to the usefulness of the delayed release enzyme breaker in cleaning filter cakes prepared from linear and borate crosslinked gels, but fluids crosslinked with metal ions were not cleaned.

Actual field trials made in a Southeastern New Mexico study wherein the delayed release enzyme breaker was used also point to the effectiveness of the delayed release enzyme breaker in improving fluid performance. Increased initial water production and sustained oil production were the results when the delayed release enzyme breaker was used. Another facet of the protection of the enzyme in high pH fracturing fluid was also examined. The delayed release enzyme breaker was successfully used in a pH 9.5 fracturing fluid.

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