Abstract: A water soluble terpolymer having the structure: ##STR1## wherein x is selected from the group consisting of ##STR2## wherein x is about 1 to about 95 mole percent; y is about 0.1 to about 5.0 mole percent; R.sub.1 is methyl or hydrogen; z is about 1 to about 30 mole percent; R.sub.2 is an alkyl group of 1-5 carbon atoms; R.sub.3 is an alkyl group of 3 to 4 carbon atoms; R.sub.4 is an alkyl group of 1-5 carbon atoms; and R.sub.5 is an alkyl group of 4-20.

Abstract: The present invention relates to improved viscosification agents for an aqueous or brine solutions. Typically, the viscosification agents are tetrapolymers of N-vinyl pyrrolidone/acrylamide/salt of acrylic acid/N-alkyl acrylamide wherein said tetrapolymers have the formula: ##STR1## wherein w is about 1 to about 80 mole percent, more preferably about 5 to about 75 mole percent, and most preferably about 10 to about 70 mole percent; x is about 10 to about 90 mole percent, more preferably about 20 to about 80 mole percent, and most preferably about 30 to about 70 mole percent; and y is about 0.1 to about 10.0 mole percent, more preferably about 0.15 to about 5.0 mole percent; and most preferably about 0.2 to about 3.0 mole percent; z is about 1.0 to about 30.0 mole percent, more preferably about 2.0 to about 25.0 mole percent, and most preferably about 5.0 to about 20.

Abstract: A water soluble terpolymer having the structure: ##STR1## wherein x is selected from the group consisting of ##STR2## wherein x is about 1 to about 95 mole percent; y is about 0.1 to about 5.0 mole percent; R.sub.1 is methyl or hydrogen; z is about 1 to about 30 mole percent; R.sub.2 is an alkyl group of 1-5 carbon atoms; R.sub.3 is an alkyl group of 3 to 4 carbon atoms; R.sub.4 is an alkyl group of 1-5 carbon atoms; and R.sub.5 is an alkyl group of 4-20.