How deep does a geothermal well need to be in order to generate steam?

Question

'well' as in water is pumped down one hole and comes out an adjacent one. Or to put it another way; How deep before the earth reaches atleast 100C?

Answer 1

The global average geothermal gradient is 0.02 K degrees per metre. Starting from an average surface temperature of 10 deg C, I make that 4500 metres to reach 100 deg C, or nearly 15000 feet.

Actually, this will not directly turn it to steam. The boiling point of water increases with pressure, and the pressure with depth, MUCH faster than the temperature increases with depth.

But as the hot water comes up, its pressure drops, so if you have gone past 4500 metres it will turn to steam just below the surface.

Answer 2

It depends on location. In Iceland there areas where steam comes up through fissures almost all of the time.
In Yellowstone Park there are permanent holes in the crust that allow water to get to hot rocks below the crust.
In my area, Southwestern PA, the estimated distance is 8000 feet.

Answer 3

60 feet