Patent ID: 7125825

Claim:
A viscoelastic fluid comprising: an aqueous medium; and an amidoamine salt surfactant having the following general structural formula: wherein, R 1 is a branched or straight chained, saturated or unsaturated aliphatic group of from about 17 to about 29 carbon atoms; R 2 is (a) a divalent alkylene group consisting of from about 2 to about 6 carbon atoms, or (b) R 2 together with R 3 form a heterocyclic 5- or 6-membered ring structure which includes the nitrogen of the amine and the nitrogen of the amide; R 3 is (a) a branched or straight chained alkyl group of from about 1 to about 6 carbon atoms or a branched or straight chained hydroxyalkyl group, or (b) R 3 together with R 2 form a heterocyclic 5- or 6-membered ring structure which includes the nitrogen of the amine and the nitrogen of the amide, or (c) R 3 together with R 4 form a heterocyclic 5- or 6-membered ring structure which includes the nitrogen of the amine; R 4 is (a) a branched or straight chained alkyl group or hydroxyalkyl group of from about 1 to about 6 carbon atoms, or (b) R 4 together with R 3 form a heterocyclic 5- or 6-membered ring structure which includes the nitrogen of the amine; X− is an anion; and the amidoamine salt surfactant is present in a sufficient amount such that the fluid at least partially recovers to an initial state after abatement of an applied stress and has properties of reversible sheer thinning.