A well servicing fluid formulated with ingredients comprising a viscosifying polymer that is a crosslinked copolymer of an ethylenically unsaturated dicarboxylic anhydride and an alkyl vinyl ether, or the di-acid thereof; a pH adjuster capable of maintaining a pH of 5.5 or greater; and a solvent. Methods of treating a well formation with the wellbore servicing fluid and methods of making the wellbore servicing fluid.