Materials such as crosslinked guar-gum derivatives have had widespread applications as viscosifying agents for water-base hydraulic fracturing fluids. Laboratory tests have demonstrated that the crosslinked gelled water viscosity will degrade with increasing temperature.

Heat-transfer simulators indicate that when there is a temperature difference between the formation temperature and the surface fluid temperature, a significant cooldown will occur across a portion of the length of the fracture. However, because of operational limitations, most treatments are designed for a worst-case temperature with, at most, two fluids of different viscosity to compensate for fluid temperature variance. Therefore, the result is a fracturing fluid with varying viscosity throughout the fracture.

Now, with the emergence of on-site microprocessors and new, accurate, continuous-mix gelling equipment, the gel loading can be varied to compensate for time and temperature effects, thus yielding a fracturing fluid with a more consistent downhole viscosity while using less gelling agent.

On-site adjustment of polymer loading gains even more utility when the net fracturing pressure is monitored for changing fracture conditions1-3 

This paper presents many of the advantages of real-time viscosity control, and several field examples that apply these features.

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