Abstract: A method for shortening the shear recovery time of zwitterionic viscoelastic surfactant fluids by adding a rheology enhancer having the structure: R-(EO)x(PO)y—R?—OH in which R is an alkyl group that is straight chained or branched, saturated or unsaturated, and contains from 3 to about 18 carbon atoms, x is from 0 to about 14, y is from 0 to about 7, R? is an alkyl group that contains from 0 to about 14 carbon atoms and is straight chained, branched if having more than 3 carbon atoms, saturated, unsaturated if having more than one carbon atom, the total number of carbon atoms in R plus R? is from 3 to about 21, and the EO and PO groups, if present, may be in any order. The rheology enhancer also increases fluid viscosity and thermal stability. Preferred surfactants are betaines. The fluids are useful in oilfield treatments, for example fracturing and gravel packing.

Abstract: A method for shortening the shear recovery time of zwitterionic viscoelastic surfactant fluids by adding a rheology enhancer having the structure: R-(EO)x(PO)y—R?—OH in which R is an alkyl group that is straight chained or branched, saturated or unsaturated, and contains from 3 to about 18 carbon atoms, x is from 0 to about 14, y is from 0 to about 7, R? is an alkyl group that contains from 0 to about 14 carbon atoms and is straight chained, branched if having more than 3 carbon atoms, saturated, unsaturated if having more than one carbon atom, the total number of carbon atoms in R plus R? is from 3 to about 21, and the EO and PO groups, if present, may be in any order. The rheology enhancer also increases fluid viscosity and thermal stability. Preferred surfactants are betaines. The fluids are useful in oilfield treatments, for example fracturing and gravel packing.