Viscoelastic surfactants and compositions containing same

A method for controlling the rheology of an aqueous system comprising:

• a) providing a gelling agent composition comprising one or more amidoamine oxide gelling agents of the general formula (I)
• wherein R1 is a saturated or unsaturated, straight or branched chain aliphatic group of from about 7 to about 30 carbon atoms, R2 is a saturated or unsaturated, substituted or unsubstituted divalent alkylene group of from 2 to about 6 carbon atoms, R3 and R4 are the same or different and are alkyl or hydroxyalkyl of from 1 to about 4 carbon atoms, or R3 and R4 together with the nitrogen atom to which they are bonded form a heterocyclic ring of up to 6 members, and R5 is hydrogen or a alkyl or hydroxyalkyl group of from 1 to about 4 carbon atoms, wherein said amidoamine oxide is in a glycol solvent and contains less than about 10% free fatty acid, and
• b) adding said gelling agent composition to an aqueous fluid in an amount effective to form a viscoelastic composition.