The invention provides a method of treating of a well, a formation, or both, with the solids, liquids, or apparatuses, by 1) encasing said solids, liquids, or apparatuses in a water-soluble shell, 2) conveying said encased solids, liquids, or apparatuses to a predetermined location in the well, and then 3) allowing the water-soluble shell to dissolve in the aqueous phase in the wellbore. The shell is preferably made of water-soluble polyvinyl alcohol copolymers and a waterproofing agent. The shell encases a variety of solids, liquids, or combinations thereof, where said solids or liquids are useful in the treatment of the well or of the producing formation. Illustrative encased material includes soap, acid, corrosion inhibitors, chelating agents, scale inhibitors, mutual solvents, paraffin inhibitors, paraffin dissolvers, clay stabilizers, and tracer materials. The encased materials may also be apparatuses, such as a prefabricated screen completion or a prefabricated sand-pack. The tool used to deliver the apparatuses may also be made from a water-soluble polyvinyl alcohol copolymer.