5 ms·

This is a tweet thread from the CEO, the article is here (but paywalled) https://www.bloomberg.com/news/articles/2023-07-18/fervo-energy-says-it-has-achieved-ge

This is a tweet thread from the CEO, the article is here (but paywalled) https://www.bloomberg.com/news/articles/2023-07-18/fervo-energy-says-it-has-achieved-geothermal-energy-tech-breakthrough https://www.bloomberg.com/news/articles/2023-07-18/fervo-ene... and what it shows is something that readers of this site should be very familiar with; technology advances impact adjacent markets "invisibly." My interest in PDC bits and the advancements in drilling related to how much simpler it would be to add fiber to the metro area by drilling horizontally 500' below street level (essentially no obstructions). The missing link there is lining the drill tube dynamically and going horizontally through water (for example) is not straight forward.

jjulius 3y ago
>... the article is here (but paywalled)... https://archive.is/0htYW https://archive.is/0htYW
nocoiner 3y ago
Is there a reason why you favor 500’ below ground level? My naive initial reaction is that seems like tremendous overkill in 99% of applications. Presumably in the vast majority of urban areas, 50’ would be more than enough to avoid any and all obstructions. I suppose once you decide to do something more than shallow trenching, then the marginal cost of additional vertical feet is fairly minor, but even in, say, NYC it seems like 500’ is way, way more buffer than you’d need in the worst case scenario (I have a vague recollection that the very deepest subway line is around 200’ underground, and that’s primarily due to a specific quirk of geography - a hill surrounded by two valleys).
- sidewndr46 3y ago
  Have you ever walked by a building under construction? It isn't uncommon to see foundation work going down >70 ft. The pilings themselves can be driven in even farther.
  - nocoiner 3y ago
    What percentage of the average urban area is covered by buildings with 70’ foundations? I assume, perhaps incorrectly, that this is something that’s only required for skyscrapers or other similar large commercial buildings? And the average CBD is, probably, what, a low single digit percentage point of the corresponding urban area? I could certainly be wrong in my assumptions (hence my question!). But it still seems to me like it would be way more efficient to drill much shallower conduits in (what I assume is) the 99.999% of geography not covered by skyscrapers (and to either go deep or continue to go targeted in the remaining fraction).
    - sambeau 3y ago
      I once sat and watched piles being driven for a small housing block, 4 stories high. These ones in fact: https://www.google.com/maps/@56.4618615,-2.9545922,3a,75y,26.85h,91.14t/data=!3m6!1e1!3m4!1sN_TqTjjAPLdiU6Bv4dfD5A!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@56.4618615,-2.9545922,3a,75y,26... Each pile was as about as high as the building. They pushed one in first and it went in like it was going through butter — literally seconds. They then stuck a second one directly on top which went in relatively easily. They then spent a thumping eternity putting a third one in on top of the other two. They repeated this process for days. So, that little building is resting on piles around 2-3 times its height.
      - jrk 3y ago
        That's a wonderfully evocative image, and I am a total non-expert so this sort of depth may be common, but I do note that that map pin is in what looks like harbor landfill. It may require an unusually deep foundation to reach bedrock there.
      - nocoiner 3y ago
        Fascinating, thanks. Do you happen to know what material they used for the piles? I’ve always assumed some kind of concrete column, but that seems possibly incompatible with the process you saw.
- voxelghost 3y ago
  Yes, now I don't know which metro-area OP was talking about but in NYC bedrock varies between a few feet to about 150 feet below the surface. http://www.classichistory.net/archives/nyc-bedrock http://www.classichistory.net/archives/nyc-bedrock (see graph. note; unit is meter)
- WarOnPrivacy 3y ago
  > Is there a reason why you favor 500’ below ground level? Florida aquifer drills are >400' to reach 65° (year round) water. Temps get really static at that level.
- ChuckMcM 3y ago
  Three reasons, temperature stability, propensity to have rock vs sediment, and in the bay area, somewhat better earthquake resistance. When I was doing ops at Blekko we had a dark fiber run between our office and the data center to get our own "high speed" connection and part of that was a geo-technical survey. Of much of the SF Bay Area peninsula. The geologist suggested if we wanted to be subterranean and avoid both infrastructure and superfund sites, that we'd have to go down 500'. He expressed doubt that anyone would do that given the expense. And there are still some parts of the Santa Clara aquifer you can hit if you don't aim well.
  - nocoiner 3y ago
    Super interesting, thanks for the response!
- jxf 3y ago
  > Presumably in the vast majority of urban areas, 50’ would be more than enough to avoid any and all obstructions. This would definitely not be enough in, say, NYC. Grand Central Station is 150 feet below street level, for example. The Oculus is about 80 feet below street level. Things are deeper than they might first appear!
eru 3y ago
Could you just add the fibre to where you already have water pipes or sewers or underground electricity lines?
aaron695 3y ago
[dead]
jjk166 3y ago
How would anyone connect to, nonetheless perform maintenance on, fiber 500' underground?

jjulius 3y ago

>... the article is here (but paywalled)... https://archive.is/0htYW https://archive.is/0htYW

nocoiner 3y ago

Is there a reason why you favor 500’ below ground level? My naive initial reaction is that seems like tremendous overkill in 99% of applications. Presumably in the vast majority of urban areas, 50’ would be more than enough to avoid any and all obstructions. I suppose once you decide to do something more than shallow trenching, then the marginal cost of additional vertical feet is fairly minor, but even in, say, NYC it seems like 500’ is way, way more buffer than you’d need in the worst case scenario (I have a vague recollection that the very deepest subway line is around 200’ underground, and that’s primarily due to a specific quirk of geography - a hill surrounded by two valleys).

sidewndr46 3y ago
Have you ever walked by a building under construction? It isn't uncommon to see foundation work going down >70 ft. The pilings themselves can be driven in even farther.
- nocoiner 3y ago
  What percentage of the average urban area is covered by buildings with 70’ foundations? I assume, perhaps incorrectly, that this is something that’s only required for skyscrapers or other similar large commercial buildings? And the average CBD is, probably, what, a low single digit percentage point of the corresponding urban area? I could certainly be wrong in my assumptions (hence my question!). But it still seems to me like it would be way more efficient to drill much shallower conduits in (what I assume is) the 99.999% of geography not covered by skyscrapers (and to either go deep or continue to go targeted in the remaining fraction).
  - sambeau 3y ago
    I once sat and watched piles being driven for a small housing block, 4 stories high. These ones in fact: https://www.google.com/maps/@56.4618615,-2.9545922,3a,75y,26.85h,91.14t/data=!3m6!1e1!3m4!1sN_TqTjjAPLdiU6Bv4dfD5A!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@56.4618615,-2.9545922,3a,75y,26... Each pile was as about as high as the building. They pushed one in first and it went in like it was going through butter — literally seconds. They then stuck a second one directly on top which went in relatively easily. They then spent a thumping eternity putting a third one in on top of the other two. They repeated this process for days. So, that little building is resting on piles around 2-3 times its height.
    - jrk 3y ago
      That's a wonderfully evocative image, and I am a total non-expert so this sort of depth may be common, but I do note that that map pin is in what looks like harbor landfill. It may require an unusually deep foundation to reach bedrock there.
    - nocoiner 3y ago
      Fascinating, thanks. Do you happen to know what material they used for the piles? I’ve always assumed some kind of concrete column, but that seems possibly incompatible with the process you saw.
voxelghost 3y ago
Yes, now I don't know which metro-area OP was talking about but in NYC bedrock varies between a few feet to about 150 feet below the surface. http://www.classichistory.net/archives/nyc-bedrock http://www.classichistory.net/archives/nyc-bedrock (see graph. note; unit is meter)
WarOnPrivacy 3y ago
> Is there a reason why you favor 500’ below ground level? Florida aquifer drills are >400' to reach 65° (year round) water. Temps get really static at that level.
ChuckMcM 3y ago
Three reasons, temperature stability, propensity to have rock vs sediment, and in the bay area, somewhat better earthquake resistance. When I was doing ops at Blekko we had a dark fiber run between our office and the data center to get our own "high speed" connection and part of that was a geo-technical survey. Of much of the SF Bay Area peninsula. The geologist suggested if we wanted to be subterranean and avoid both infrastructure and superfund sites, that we'd have to go down 500'. He expressed doubt that anyone would do that given the expense. And there are still some parts of the Santa Clara aquifer you can hit if you don't aim well.
- nocoiner 3y ago
  Super interesting, thanks for the response!
jxf 3y ago
> Presumably in the vast majority of urban areas, 50’ would be more than enough to avoid any and all obstructions. This would definitely not be enough in, say, NYC. Grand Central Station is 150 feet below street level, for example. The Oculus is about 80 feet below street level. Things are deeper than they might first appear!

eru 3y ago

Could you just add the fibre to where you already have water pipes or sewers or underground electricity lines?

aaron695 3y ago

[dead]

jjk166 3y ago

How would anyone connect to, nonetheless perform maintenance on, fiber 500' underground?