Successful hydraulic fracturing requires proper proppant placement within an adequate fracture length. To accomplish this, one must design a fracturing fluid that can achieve effective proppant placement and retain desirable fluid properties under hydraulic fracturing conditions within the reservoir. Recently, there have been reports that increased pressure on the fluid may reduce the viscosity of borate-crosslinked fracturing fluids. Depending on fluid composition and operating temperature, the effects of applied pressure vary from slightly influencing to completely reducing the viscosity of the crosslinked sample to its un-crosslinked state (linear gel). Thus, a good understanding of the impact of applied pressure on viscosity of fracturing fluids in the laboratory is critical to designing and tailoring fluid formulations. This work describes the equipment and experimental procedures for high pressure rheology testing of selected seawater and higher density brine-based borate crosslinked fracturing fluids in the shear rate range of 20 to 80 s-1, up to 20,000 psi and 180°F.

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