The DoE is trying to convert some of the millions of abandoned oil and gas wells for geothermal energy.

[Xist]

I think that it is an interesting idea, but I didn't think the common knowledge and politics in the first couple paragraphs were relevant, nor did I see any details worth sharing, but what else would we do with millions of abandoned wells?
https://www.vox.com/recode/23024204/...-oil-gas-wells

[freebeard]

I'd have sworn affirmed that I posted about Quaise, but Google can't find it.

https://newatlas.com: Quaise's ultra-deep geothermal drilling plans: Your questions answered

Quaise's ultra-deep geothermal power plan is one of the most exciting and fascinating green energy projects we've seen. In a nutshell, this Boston-based MIT spin-off says it has repurposed powerful millimeter-wave beam technology – originally developed to superheat plasma in fusion experiments – to blast through previously undrillable rock far below the Earth's surface.

The company says this will allow it to drill bore holes far deeper than has ever previously been possible, going down far enough to access rock temperatures around 500 °C (932 °F). That's well past the point where water becomes heated to a "supercritical" state that radically boosts the efficiency of geothermal power extraction.

The end result: massive, virtually inexhaustible geothermal energy resources will become available practically anywhere on the planet. More or less any existing power station that uses fossil-fueled heat to create steam and run turbines can be connected to a totally reliable, 24-hour supply of green energy that'll keep those turbines turning without a single puff of CO2 escaping, and without the worrying intermittency of other renewable sources like wind and solar energy.

One hole isn't enough, you need a re-injection well.

[Xist]

Do you think any gas and\or oil wells are close enough to conveniently form a circuit?

[Piotrsko]

To answer that question: SWEPA in Bakersfield, more aptly, buttonwillow/ petroleum reserve has wells spaced about 1/4 mile apart that tapped the same source.

New question: since it is known we go at least 2-3miles deep with current technology, how much deeper do you need?

[freebeard]

Old answer: Permalink 2

TLDR: 3x the deepest existing well to get supercritical steam.

Coal fired turbine generators are the best sites to start with. They have existing infrastructure for electricity, not pumping fluids.

[aerohead]

The steam provided to the turbine must be exceptionally clean and dry, in order to not erode the super-expensive turbine blades.
Seems like it would have to be in its own closed-loop, as in any thermal-powered power plant, traveling to and from the heat source via a heat-exchanger, or the hot well working fluid traveling from the bore-hole to and from the heat-exchanger.
Carson City, Nevada sits atop a super-volcano caldera, and they tap this as a source of 'shallow' heat.
Seems like these 'shallow', thin lithosphere locations, close to the magma, would be the 1st-choice locations. They'd require the minimum drilling and completion costs, plus get into service the quickest, all else being equal.

[freebeard]

Seems like these 'shallow', thin lithosphere locations, close to the magma, would be the 1st-choice locations.

Your search term: '[*your_state} hot springs'

I like the concept of the water-to-water-to-air heat exchanger. A tank at the bottom of a well with two pipes down to it, and a DNA spiral inside the tank. The 'dirty' water never goes anywhere.

For economical reasoning purposes, lower tank is 6-8" PVC tens of feet long, with a loose copper spiral.

[aerohead]

Originally Posted by freebeard

Your search term: '[*your_state} hot springs'

I like the concept of the water-to-water-to-air heat exchanger. A tank at the bottom of a well with two pipes down to it, and a DNA spiral inside the tank. The 'dirty' water never goes anywhere.

For economical reasoning purposes, lower tank is 6-8" PVC tens of feet long, with a loose copper spiral.

Turbines would require 500-F, dry, super-heated stream, requiring equivalent down-hole temperature.
Way beyond the capability of PVC plastic.
If corrosive hot brine were present, we'd be looking at stainless steel.

[freebeard]

Stainless steel tank, copper heat transfer area, and PEX to the surface?

Supercritical steam requires millimeter wavelength lasers to vitrify the walls. Way beyond DIY.

[aerohead]

Originally Posted by freebeard

Stainless steel tank, copper heat transfer area, and PEX to the surface?

Supercritical steam requires millimeter wavelength lasers to vitrify the walls. Way beyond DIY.

We should look at 'what works' ( Matt Damon ).
I can't envision vertical, multi-mile length copper pipe. I don't think it has the tensile strength to survive.
Pex, as with Poly Vinyl Chloride couldn't hold up to the heat.