[pixl97]

>The usable energy is proportional to the cross-section of the borehole

I mean we thought oil the same way until we developed fracking. While it's not likely a 1:1 relationship with fracking, I'm sure some clever geologists/drilling experts could massively increase the surface area available for heating given the right incentives.

As for facilities, the volcano eruption rate is rather low on human timescales, especially for effusive eruptions that don't tend to blow the entire area to bits. Getting 50-100 years between eruptions that could possibly total the facility is likely worth it as you don't have a direct fuel cost.

[jackfoxy]

What? No. It's how much fluid (not how much heat) and the oil cut of the fluid you are pumping up the borehole in the O&G industry. This has no bearing on whether the hole is fracked. It's a matter of the decline curve of the well. Not every well in amenable to fracking, and there are techniques other that fracking that will lift the decline curve, but then it starts declining again.

But this is neither here nor there. The energy you extract from a geothermal well is heat, which then needs to be converted to electricity. The BTUs in a good oil or gas well exceed those of a geothermal well. You have the same issues of the well becoming less productive. The remediation strategies for this are similar, i.e. pumping fluid back into the ground.