Patent ID: 7345012

Claim:
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 recovery time at relatively low shear conditions following a reduced viscosity from high shear conditions, b. generating a foam from said fluid, c. adding to said fluid a foam stabilizer in a concentration sufficient to increase the thermal stability of said foam, said foam stabilizer being a polymer comprising at least one portion selected from at least one of partially hydrolyzed polyvinyl esters; and d. injecting said fluid down a well, wherein the foam has a viscosity ratio of at least about 2 over the temperature range from 65° C. to 150° C. and wherein the fluid has a foam quality from about 55 to 80 percent, further comprising injecting the foam from the wellbore into an adjacent subterranean formation.