I spoke to a horizontal well driller about this and he was more than happy about the prospect of a boom in solar, partly because he was interested in trying out jobs in the industry. He also had an eye on the geothermal business as he could take his existing skill-set there. Also, while coal mining may collapse, I do not see a collapse in mining happening any time soon. The biggest threat to the overall number of mining jobs is robotics, not solar.
Drilling should translate quite well to enhanced geothermal, though I've got my doubts on total potential there. See Australia's Habernero Pilot Plant (Geodynamics). The project has seen multiple setbacks and been scaled back significantly from initial expectations, while costs were well above initial estimates.
Wet-field geothermal, with live steam, is a proven and viable technology, with decades of proven use. It's still got pretty limited overall potential, though it could reach 10-20% of electricity generation needs at present rates in the US, Japan, the Philippines, New Zealand, and possibly elsewhere. In Kenya, it could provide a large portion (possibly multiples) of present generating capacity.
