I also read that Quaise value proposal is drilling a 20km deep hole but once you reach there, how do you transform that into usable energy? Push water to extract vapor?
To your question, I'm wondering if they simply pump down water and extract resulting steam once it reaches the point of vaporization? The steam condensers and everything else are already built on-site for coal generation.
One difficulty would be handling any accumulated minerals that got into the steam loop from interaction with the rock in the hole. Unlike traditional closed-loop steam generator, an open system would pick up contaminants and eventually cause scaling.