Patent ID: 8418764

Claim:
A method of controlling fluid loss in a subterranean formation comprising: providing a treatment fluid comprising an aqueous fluid and a fluid loss control additive, the fluid loss control additive comprising a hydrophilically modified water-soluble polymer comprising a reaction product of a hydrophilic compound and a hydrophilic polymer; wherein the hydrophilic compound is selected from the group consisting of: a polyether comprising a halogen, a sulfonate, a sulfate, an organic acid, an organic acid derivative, and a combination thereof; wherein the hydrophilic polymer is selected from the group consisting of: a polyvinylamine, a poly(vinylamine/vinyl alcohol), and a combination thereof; introducing the treatment fluid into a portion of a subterranean formation wherein the hydrophilically modified water-soluble polymer reduces the permeability of the portion of the subterranean formation to aqueous fluids without substantially reducing the permeability to hydrocarbons so that fluid loss from the aqueous fluid into the portion of the subterranean formation is reduced.