Abstract: The device proposed has a pipe (3) sunk into the Earth's crust and designed to convey to the surface a fluid heated by geothermal energy, possibly in vapor form. The device also has a second, outer, pipe (2) surrounding the conveyor pipe and designed to carry the fluid back into the Earth, as well as an end cap (4) which forms a pressure-tight closure over the end of the outer pipe to prevent the ingress of the surrounding rock, etc., the conveyor pipe being joined to the outer pipe at the bottom, in the region of the closure.