Hydraulic fracturing often employs crosslinked polymeric gels, which 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. Crosslinking of a polymeric gel can significantly contribute to the success or failure of a fracturing treatment. Crosslinking agents used in commercial fracturing applications include borate, titanium, and zirconium (Zr) complex ions.

As the 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 can lead to compromising of near-wellbore (NWB) proppant transport and reduced fracture width, 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 that does not reheal 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 fracturing fluid for high-temperature applications with a delay of complete crosslinking until after the fluid is beyond the high shear environment. Rheological characterization was performed with a Model 50-type viscometer at temperatures greater than 300°F, including shear-history profiles. The fluid chemistry presented employs a zirconium crosslinker and buffer combination that controls the crosslinker kinetics to yield a viscoelastic gel crosslink after passing through the high shear-history profile. Additionally, regained-permeability results obtained using conventional breakers demonstrated the fracturing fluid's cleanup efficiency.

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