Patent ID: 8575075

Claim:
A method of providing controlled viscosity-reducing activity in a well treatment fluid comprising introducing, into an aqueous well treatment fluid composition comprising a polymer or copolymer for increasing fluid viscosity or otherwise modifying fluid viscosity of the aqueous fluid composition, an agent for effecting a controlled reduction in the aqueous fluid viscosity in a subterranean environment; the viscosity-reducing agent comprising a peracetic acid in an amount of about 50 ppm to about 200 ppm wherein such amount is sufficient to provide viscosity reduction of the aqueous well treatment fluid composition in the subterranean environment to less than about 100 cP; adjusting the pH of the aqueous fluid composition, as necessary, to a pH value in the range of 7 to 10; and directing the aqueous well treatment fluid composition into a subterranean environment for which treatment is desired, the ground temperature of the subterranean environment being at least about 30° C.