Using a Model 50 Fann viscometer, the viscous behavior of a delayed-crosslink fracturing fluid was evaluated after the fluid was subjected to various combinations of thermal and shear history. Fluid thermal and shear histories were created by pumping a mixture of polymer solution and crosslinking additive through tubing coils situated in a series of thermally-controlled baths. Specifications of the preconditioning device are provided in the paper. By varying bath temperatures and flow rates through the preconditioning coils, it was possible to create a wide variety of fluid thermal and shear histories. An organo-metallic crosslinking agent was continuously mixed into the polymer solution as it was being injected into the preconditioning device. At the point where the chemically reacting mixture exited the preshear device, it was routed, without stopping, into a rotating viscometer cup by means of a quick-connect. In this manner, the fluid sample captured within the viscometer cup experienced a continuous shearing action similar to that experienced in the field environment. Sample rheology was then monitored over a 2-hour period at elevated temperature using a R1 B5 X measurement configuration. The merits of using the R1 B5 X rather than the wide gap R1 B2X measurement configuration are discussed. Rheology results from nine uniquely different thermal-shear history combinations were compared to determine the relative influence of each parameter on the final fluid viscosity.

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