Abstract: A method and apparatus for cleaning openings in a borehole casing, slotted liner, screen or the like, cleaning subsurface earth formations and/or stimulating the flow of fluids through subsurface earth formations surrounding a borehole in which a plasma is generated adjacent the area to be treated by the gasification and ionization of a gasifiable and ionizable material, such as, water, petroleum or similar fluids and/or solids, such as, a consumable metal wire, thereby creating an intense shock wave which passes into or through the material being treated. The plasma region is created by any means adapted to gasify and ionize the gasifiable and ionizable material, such as, a high voltage, high current electrical discharge of short duration.