Crosslinked polymers that may be useful, for example, as viscosifiers or fluid-loss control additives for well treatment and servicing fluids are provided. In one embodiment, the methods comprise: providing a treatment fluid comprising a base fluid and a crosslinked polymer composition comprising at least one polymer that comprise at least one N-vinyl lactam monomeric unit, and at least one crosslinker selected from the group consisting of: an acrylamide-based crosslinker, an acrylate-based crosslinker, an ester-based crosslinker, an amide-based crosslinker, any derivative thereof, and any combination thereof; and introducing the treatment fluid into at least a portion of a wellbore penetrating at least a portion of a subterranean formation.