Enzymatic Breaker

Enzymes to degrade crosslinked hydroxypropylated starch derivative and xanthan gum polymer systems are available [158,1246]. Specific enzymes are efficient in reducing the near wellbore damage induced by the starch polymer to eventually return permeabilities to the range of 80% to 98% without the use of acid systems. 

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Size exclusion chromatography [240,665] has been used to monitor the degradation of the thickeners initiated by various oxidative and enzymatic breakers. 

At the end of the hydraulic fracturing process, and when gels are employed, these must be destroyed to allow fluids to flow freely through the freshly fractured zones and benefit from the permeability improvements achieved by fracturing. Chemical or enzymatic gel breakers are employed for this purpose. Traditionally, enzymatic breakers operate under mildly acidic conditions at low temperatures, while oxidizing chemical breakers operate at moderate-to-high... 

Borate cross-linked fracture fluids are also believed to cause less damage to the reservoir and less likely to impair permeability than rival cross-linkers [26,50,68], This is partly due to the fact that borate cross-links can be broken down after fracturing simply by reducing pH. That is not to say that chemical (oxidative) or enzymatic means for effecting cleanup of the reservoir are not required to break down the polymer chains and flush away the fluid residues, but this process is more effective with borates because of the reversible nature of the cross-link bond. Some metal ion cross-linked gels have poor cleanup properties and soluble precipitates can be formed when they react with certain chemical breakers. ... 

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