A method and apparatus are described for creating a fluid seal in a subterranean well structure having a fluid seal defect. The method comprises introducing a meltable
repair material proximate a structure in a subterranean well which has a fluid seal defect or enhanced seal capacity is required or it is desired to temporarily or permanently hydraulically isolate a portion the well or strengthen the
structural integrity of well tubulars or tubular hangers. Exothermic reactant materials are located
proximate the meltable
repair material. The exothermic reactant material is ignited or an
exothermic reaction otherwise initiated which supplies heat to and melts the meltable
repair material into a molten
mass. The molten
mass flows and solidifies across the structure and the fluid seal defect to effect a fluid seal in the subterranean well structure or the
structural integrity is enhanced. Examples of preferred exothermic reactant materials include
thermite, thermate, fusible chemical reactants such as
ammonium chloride and
sodium nitrate, and oxidizers and accompanying
hydrocarbon based fuels. Examples of preferred meltable repair materials include solder or
brazing materials and eutectic metals which expand upon cooling and solidifying from a
molten state.