Hydraulic fracturing employs crosslinked polymeric gels that are pumped into a subterranean formation with sufficient viscosity properties to generate fracture geometry in the subterranean rock and transport solid proppants to hold the fracture open. The extent of crosslinking a polymeric gel can significantly contribute to success or failure of a fracturing treatment. Crosslinking agents used in commercial fracturing applications include borate, titanium, and zirconium (Zr) complex ions.

As fracturing fluid is pumped downhole, it experiences different shears, such as high shear caused by tubulars and low shear in the fracture. Typically, polymeric gels are shear-thinning and will reduce in viscosity on application of high shear. The fracturing fluid's inability to shear-recover as it transitions from a high-shear regime in tubulars to a low-shear regime as it enters the fracture will lead to compromising of near-wellbore (NWB) proppant transport, and treatment can screenout. Borate crosslinkers that are known to provide the shear-recovery property to the fracturing gel typically have a temperature limitation of 300°F. Conversely, metal crosslinkers that have good temperature stability beyond 300°F are prone to irreversible shear degradation as the fluid passes from the high-shear to a low-shear regime, thus compromising efficient proppant transportation inside the fracture.

This paper presents the development of a novel shear-stable fracturing fluid for high-temperature applications. Rheological characterization was performed with a Fann Model 50-type viscometer at temperatures greater than 300°F using typical wellbore shear rates including shear-history profiles. The fluid chemistry of a Zr crosslinker and buffer combination that controls the crosslinker kinetics to yield shear-resilient and shear-recoverable viscoelastic gel after passing through the shear-history profile is presented. Additionally presented are regained permeability results obtained using conventional breakers that demonstrated the frac fluid's cleanup property.

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