Device used in the form of a packer or a temporary plug

A device functioning as a packer or temporary plug including a case, and transformable into a device preventing oil-well fluid passage in which the device and a liquid-passage preventing substance is located, wherein the liquid-passage preventing substance is a pack of fibres made of organic or natural polymers and/or glass fibre, wherein the case is expanded in-well by a spring or hinged umbrella mechanism, wherein the case is made of materials at least low-soluble in the oil-well fluid, and wherein the case self-destructs or decomposes in a well environment during a wellbore activity.