A composition made of fibers and a material able to exhibit reverse solubility has utility for treating subterranean wells. The composition may used to cure lost circulation. The composition may be added to drilling fluids, spacer fluids or cement slurries. As the fluid temperature increases in a well, the reverse solubility material may precipitate and migrate to the fibers, causing the fibers to stick to each other and form a network, thereby forming a barrier that reduces further egress of treatment fluid from the wellbore.