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. nostrademons · 1789610643 · focus · HN ↗
  There was a good comment on r/oil by someone who worked on the engineering for the SPR. Unfortunately it's fallen off the front page and I can't find it now, but:
  > 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.
  It turns out that it's trivially easy to prevent the water from leeching out the salt. They presaturate the water with salt, so that it already contains the maximum amount of salt that can be dissolved for a given temperature. When they pump the brine out, it goes into aboveground brine pools that can easily be seen on satellite imagery. The salinity of this brine can easily be controlled: if you want to expand the cavern, you mix it with freshwater so the brine dissolves more of the edges, if you don't you pump it back in as brine.
  Edit: Here, found some satellite imagery of one of the SPR sites:
  <a href="https://maps.app.goo.gl/B8XJ9TVhQfcdErky5" rel="nofollow">https://maps.app.goo.gl/B8XJ9TVhQfcdErky5
  You can clearly see the brine pond, which is as big as the aboveground portion of the SPR itself.
  1. raducu · 1789641388 · focus · HN ↗
    > the brine pond.
    Then why not store the oil there directly instead of going all the trouble of pumping it in and out of the caverns? Is it so it doesn't rain on it?
    simmonmt · 1789642324 · focus · HN ↗
    Crude oil is sketchy stuff. All sorts of VOCs, etc evaporate from it. Some valuable, some, flammable, some will merely kill you. Keeping it confined makes all that more manageable.
    jkahrs595 · 1789644393 · focus · HN ↗
    TFA lays it all out, oil out in the open is exposed to attack/lightning strikes/etc.
    huurtehoog · 1789649306 · focus · HN ↗
    Are you advocating for long term crude oil storage in open air oil lakes?
    Tangurena2 · 1789649914 · focus · HN ↗
    If the sides of the pond collapse (which happens a lot with mine tailings), then you have something resembling a oil pipeline rupture (which also happens a lot, but some states make it illegal to get video footage of it) which is a rather toxic situation needing soil to be bulldozed and either buried or burned.
    noselasd · 1789660647 · focus · HN ↗
    Sun, rain, hurricanes, wind, debris is not friendly to long term oil storage.

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