A process for gelling a fluid having a viscosity of at least about 50 cps which includes the steps of: forming a solvent system of the nonpolar organic liquid and a polar cosolvent, the polar cosolvent being less than about 15 weight percent of the solvent system and a viscosity of the solvent system being less than about 100 cps; dissolving a water insoluble, oil soluble terpolymer in the solvent system to form a solution, a concentration of the terpolymer in the solution being about 0.2 to about 10 weight percent and a viscosity of the solution being less than about 2000 cps, the terpolymer having the formula: ##STR1## wherein x is about 40 to about 98 mole %, y is about 1 to about 50 mole %, and z is about 1 to about 50 mole %, wherein y and z are less than 60 mole %, and M is an amine or a metal cation selected from the group consisting of antimony tin, lead, Groups IA, IIA, IB and IIB of the Periodic Table of Elements; and adding about 5 to about 500 volume percent water to the solution of the terpolymer, said water being immiscible with the solution of the terpolymer, the polar cosolvent transferring from the nonpolar organic liquid to the water thereby causing the viscosity of the organic liquid to increase to at least 5000 cps.