Methods for forming a fluid seal in a subterranean formation may comprise: providing a treatment fluid comprising an aqueous carrier fluid, a sealant composition, and a crosslinked polysaccharide composition. The treatment fluid is introduced into a wellbore penetrating a subterranean formation and the crosslinked polysaccharide composition is formed into a viscosified gel in the wellbore. The viscosified gel substantially spans the diameter of the wellbore and holds the sealant composition in place. After forming the crosslinked polysaccharide composition into a viscosified gel in the wellbore, forming a fluid seal in the wellbore with the sealant composition.