A fluid containing a viscous hyposaline aqueous solution of first and second cationic polymers that include quatemized ammonium groups, wherein the first cationic polymer includes a hydrophilic base polymer structure and the second cationic polymer includes a lipophilic base polymer Also disclosed is a method of introducing the viscous fluid into an initial first interval of a subterranean formation, and diverting with the viscous fluid a treating fluid from the initial first interval to an initial second interval.