Thread

The engineering behind the US Strategic Petroleum Reserve

281 points · 115 comments · johnjwang

anigbrowl · 1789601755 · focus · HN ↗
Salt contains the oil and helps seal small fractures. The rock salt surrounding the SPR’s caverns has extremely low permeability, meaning fluids have very little ability to pass through it. It also doesn’t react with petroleum. Under enormous pressures underground, salt also slowly deforms, which helps close small fractures. The salt itself can therefore contain the oil without a steel-and-concrete tank lining the cavern.
Oil floats on water, which means pumping water into the bottom of the cavern pushes the oil out. As fresh water is pumped into the bottom of the cavern, the oil gets displaced upwards into a delivery system.
The more water you pump in, the lower the quality of the oil that's pumped out; we are basically loaning the oil refiners money to buy SPR oil they don't really want. Also, the more water we pump in, the more salt leeches into the water and the more the bottom of the chamber deforms, creating shear forces in the upp walls that lower its overall structural integrity.
I've posted this before; it's a recent report on the status and maintenance of SPR facilities, which is very clearly written and well worth your time if you want to understand the topic better: <a href="https://www.gao.gov/products/gao-26-106918" rel="nofollow">https://www.gao.gov/products/gao-26-106918
1. Morromist · 1789609671 · focus · HN ↗
  It would be cool to see what these look like in a photo but I guess they're never empty of liquid. I wonder what happens to the oily water after we use it? Do we boil it until it evaporates?
  1. greggsy · 1789641974 · focus · HN ↗
    There’s a 3D model of the caverns here <a href="https://www.spglobal.com/energy/en/news-research/blog/crude-oil/061516-a-rare-tour-of-the-strategic-petroleum-reserve" rel="nofollow">https://www.spglobal.com/energy/en/news-research/blog/crude-...
    Morromist · 1789692159 · focus · HN ↗
    Wow that is very very cool. Thank you very much for digging that up & sharing the link! Sometimes visuals like that really help me process information.

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