The climate change movement: July 28, 1995 to August 14, 2020 RIP

[redpoint5]

"Oil window", in that context seems to suggest there is a max temperature that oil or gas can be extracted. It doesn't suggest what is sensitive to temperatures above that, or what those max temperatures are.

Temperature rises surprisingly quickly as depth increases. Perhaps the dry and abandoned holes could be repurposed into geothermal electricity generation plants?

[aerohead]

Originally Posted by redpoint5

"Oil window", in that context seems to suggest there is a max temperature that oil or gas can be extracted. It doesn't suggest what is sensitive to temperatures above that, or what those max temperatures are.

Temperature rises surprisingly quickly as depth increases. Perhaps the dry and abandoned holes could be repurposed into geothermal electricity generation plants?

It will be a combination of bottomhole temp. and pressure together.
All Gulf of Mexico wells, 20,000-28,000-feet ( True Vertical Depth ), producing oil are at less than 300-F.
Deeper wells are producing natural gas.
An onshore, Bertha No.1 well in Oklahoma, at 31,441-feet TVD, was @ 24,850-psi, and 475-F, and produced only liquid sulfur.
The petroleum geologist elected to complete the well @ 13,000-feet, and it produced natural gas for awhile before playing out.
A $7,000,000 'ultra-deep dry hole.'
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Carbonate rock is a VERY good thermal insulator. The thickness of the crust shields the formation from the heat below, which statistically would be outside the 'oil window'. ( 1,800-F ( 1,000-C ) at below the crust )
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wattsupwithat.com is good about parsing out what the actual 'depth' of a well is exactly.
A 40,000-foot well can have: 11,000-feet of actual vertical depth, plus 29,000-feet of slant-drilled horizontal 'depth.'
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Also, if you look at all the vertical cross-sections of the well bore, you notice that everything is sedimentary, or mild-metamorphic rock.
Formerly continental, continental shelf, or sea floor, which was buried and then subducted during tectonic activity.
Virtually all the petroleum and gas is of terrestrial, or near-terrestrial origin.
The ocean floor has been recycled and renewed at least 24-times since Earth formed.

[aerohead]

Continental crust has an average geothermal gradient of 55-F per mile ( 20-C/km ).
According to Halliburton Oil Well Cementing Company, average continental crustal thermal gradients will produce:
110-F @ 2,000-FT
140-F @ 4,000-FT
170-F @ 6,000-FT
200-F @ 8,000-FT
230-F @ 10,000-FT
260-F @ 12,000-FT
290-F @ 14,000-FT

In California, the USDOE had a geothermal well in Long Valley, at 6,000-10,000 feet, near a dormant volcano.
At 20,000-feet, it is 1200-C ( 2160-F ).
Northern California geothermal takes advantage of near-surface volcanism as well.
Carson City, Nevada has active geothermal electric power generation. It's a caldera for a super-volcano, like Yellowstone, Wyoming.
Seems like, unless there's magma nearby, a 'typical' hole in the ground cannot provide 'commercial' levels of ambient heat for the necessary super-heated steam.

[oil pan 4]

Easy solution to that problem is don't use superheated steam to drive the turbine.

[skyking]

That doesn't really address the problem, because of the insulative nature of that ground. Once you start extracting it starts cooling off rapidly. You need that high temperature differential so you can pull a lot of heat out of there with relatively little drilling and piping.
We bang into that insulative property problem with our ground source heat pumps. In the winter, the ground gets frozen around the coils from extracting heat.

[aerohead]

Originally Posted by skyking

That doesn't really address the problem, because of the insulative nature of that ground. Once you start extracting it starts cooling off rapidly. You need that high temperature differential so you can pull a lot of heat out of there with relatively little drilling and piping.
We bang into that insulative property problem with our ground source heat pumps. In the winter, the ground gets frozen around the coils from extracting heat.

The DOE hydro-fracs their geothermal wells to blow the strata open, and keep it open with aggregate, amplifying its effective heat transfer surface area and working fluid permeability.
The rock is basaltic, like glass, and has a much higher heat transfer coefficient than sedimentary rock, where methane and liquid hydrocarbons would be found in the oil patch.

[aerohead]

Originally Posted by oil pan 4

Easy solution to that problem is don't use superheated steam to drive the turbine.

Do they do that?
When we did the three nukes at Palo Verde, west of Phoenix, is was still 500-F, dry steam, for the Westinghouse turbines. They couldn't allow any chance of condensate striking any stage of the turbine blades.

[freebeard]

I was cryptic in the Wind Turbine thread, because it was off topic.

DDG?q=millimeter+wave+geothermal&ia=web

Better? Picture?



www.thinkgeoenergy.com/research-partnership-to-explore-ultra-deep-geothermal-drilling/

Go deep or go home.

[redpoint5]

Seems to me the problem of not enough heat extraction has a few possible solutions.

Increase the volume, especially the surface area of the "hot pocket"
Use the thermal conductivity of water to extract the heat
Drill near volcanically active areas to increase the temperature

I've always wondered why a heat pump couldn't be used to achieve the necessary temperature for steam generation? They're at least 300% efficient, so in theory one should be able to run a steam turbine from a heat pump and have a net gain in electricity, especially if you're already starting with pretty hot temperatures.

[freebeard]

Stirling engine
A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas between different temperatures, resulting in a net conversion of heat energy to mechanical work. More specifically, the Stirling engine is a closed-cycle regenerative heat engine with a permanent gaseous working fluid. Wikipedia

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