There is a new company, with new technology that they say can possibly drill down to 20Km.
Why is this important? It’s very hot down there, 500C, hotter than a nuclear reactor and certainly much cleaner. There is all of the energy that the planet needs down there.
IMO, the idea is to use extremely high frequency radio waves to melt the wall of the borehole into a sort of volcanic glass obviating the need to use traditional methods to make a very very long casing underground…
Worth a look…