But that doesn’t address slight shifts causing the hole casing to crack and seal. Longer the hole, greater the odds of that happening, and the greater the time and money to repair.
Yes and no. There will always be slight movement but absent earthquakes ground shift is usually minimal closer to the surface. This is how/why we have 50 year old plus oil wells at very deep depths. The outer crust of our planet is relatively stable absent earthquakes.
My primary concern about this idea is how would you prevent upward migration of magma given the probable pressures.
It is an interesting concept.