Terpolymers of acrylamide, alkyl polyetheroxyacrylate and betaine monomers

A method for increasing the viscosity of an aqueous solution which comprises the step of dissolving in said aqueous solution a water or brine soluble terpolymer having the structure:

• ##STR15## wherein x is selected from the group consisting of ##STR16## wherein x is about 70 to about 95 mole percent;
• y is about 0.1 to about 5.0 mole percent;
• z is about 1 to about 30 mole percent;
• R.sub.1 is methyl or hydrogen;
• R.sub.3 is an alkyl group of 3 to 4 carbon atoms;
• R.sub.4 is an alkyl group of 1 to 5 carbon atoms;
• R.sub.5 is selected from the group consisting of an alkyl group having 1 to 30 carbons, a hydrocarbon aryl group having 6 to 20 carbons and an alkylaryl group having the structure of ##STR17## wherein A is selected from the group consisting of hydrogen, methyl groups, ethyl groups and propyl groups and mixtures thereof and c is about 6 to about 20;
• and n is about 1 to about 60;
• wherein the aqueous solution is selected from the group consisting of water or salt solution, wherein the salt concentration is about 0.01 to about 20 weight percent.