Abstract: 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.

Abstract: A fluid comprising a viscous hyposaline aqueous solution of first and second cationic polymers comprising quaternized ammonium groups, wherein the first cationic polymer comprises a hydrophilic base polymer structure and the second cationic polymer comprises a lipophilic base polymer structure, and a method comprising 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. The fluid and method are useful to modify a hydrocarbon reservoir formation for improved relative permeability of oil with respect to water to enhance hydrocarbon production from the reservoir.