Abstract: A method of hydraulic fracturing is provided in which at least two separate fracturing fluid components are pumped downhole, one of said components being pumped downhole within coiled tubing. The fracturing fluid components responsible for increasing or decreasing the viscosity of the fracturing fluid are provided downhole separately from the polymer which is to be crosslinked, facilitating a delay in the onset of viscosity increase until the fluid has traveled a substantial distance downhole. Downhole pressures may be determined by measuring the pressure in coiled tubing while the fluid within the coiled tubing is in a non-dynamic condition. In some instances, the fluid can be used to plug or seal the formation from producing undesirable fluids, such as water.