Patent ID: 7402549
Filing Date: 2008-07-22
Classification: C09K

Abstract:
1. An oilfield treatment method comprising: a. viscosifying a fluid with a viscoelastic surfactant system comprising a viscoelastic surfactant selected from at least one of zwitterionic, amphoteric, and cationic surfactants and mixtures thereof, wherein the viscosified fluid has a rheology comprising a viscosity and a viscosity recovery time at low shear conditions following a reduced viscosity from high shear conditions, b. providing a rheology enhancer in the fluid at a concentration sufficient to shorten the viscosity recovery time of the viscoelastic surfactant system, said rheology enhancer selected from at least one partially hydrolyzed polyvinyl ester; and c. injecting said fluid down a well through tubulars into a subterranean formation, wherein the high shear conditions are the conditions in the tubulars and the low shear conditions are the conditions in the formation, and wherein the viscosified fluid is subjected to high shear conditions for at least about 30 seconds to reduce the viscosity and then the viscosified fluid is subjected to reduced shear to recover the viscosity.