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gruez | on: The engineering behind the US Strategic Petroleum Reserve
We can't pump saturated salt solution to prevent more salt from being dissolved?
smallmancontrov | parent | next
Seawater is 10% saturated IIRC, so you'd have to make the saturated solution first, and if the easiest way to do that is to dissolve another cavern then using brine doesn't have much of a cost advantage over "use this one until it collapses, then dissolve the rubble or make another."
seb1204 | root | parent
I disagree that there is no cost associated with making another. Externalising environmental and rectification cost should not be the default approach.
chabska | parent | next
If you're gonna build a bunch of tanks on the surface to store that saturated salt solutions, you might as well store the oil in those tanks. The point of this salt cavern system is how little infrastructure it needs to store the huge volume of liquid.
wildzzz | root | parent | next
Yes but the risks associated with storing brine are far less than oil. Brine leaks out? It might kill the flora nearby but rain will eventually wash it away. Someone blows up the brine tank? Divert some freshwater until you can rebuild.

But in reality, storing all of that brine would be a massive undertaking on its own. The largest salt cavern is 37M barrels which equates to a circular pond that's 600m across and 20m deep. That's huge. And of course you don't want the brine seeping into the ground water so it needs a good liner. But I suppose you really don't need a pond that big, how often are we completely draining the cavern anyway? We're at half capacity right now and that's the lowest it's been in 50 years. Normally it's been much much higher. So you really don't need all that brine, just enough for the normal ebb and flow of the reserves, maybe like 10%. In the event the reserves get drained, divert some freshwater to compensate.

tedd4u | root | parent
Do they really have brine storage tanks for enough brine to pump out all the oil? If true, they would have just exectly the right volume of above-ground tanks to just store the oil in the first place and not mess with all these caverns and brine and whatnot.
fourthark | root | parent | next
That doesn't solve the someone-might-blow-it-up design problem cited in TFA.
Kerbonut | root | parent
They most likely truck in the brine from a mixing facility to reclaim the oil and truck out the brine to disposal when refilling the oil stock.
nine_k | root | parent | next
> as well store the oil in those tanks

Salt does not burn, unlike oil. It would be sufficient to store dry salt, and prepare the brine during the pumping. Still a lot of hassle, of course.

chabska | root | parent
Please, literally every other country in the world store their petroleum reserve in surface tanks. We have fifty years of experience in designing the safety systems around oil tanks, and the only recent major incidents are from drone strikes in Russia and Saudi Arabia. Just because the US luck out in having the specific geological formation to store oil cheaply doesn't mean the alternative is untenable.

> It would be sufficient to store dry salt

Absolutely impractical. Storing and moving around solids in the megatons is very difficult compared to liquids that can be pumped. For comparison, the absolute largest solids moving operation in the world is a copper mine in Chile, it moves 300,000 metric tonne of mineral per day. The east-west pipeline in Saudi Arabia can move three times that in liquid, 1,000,000 metric tonne per day.

dd8601fn | root | parent
This method appears to be, in nearly every way, far better suited for purpose.
justinator | root | parent | next
Just spitballing here, can't you just store the salt alone and make the hyper-saturated salt water on the fly? That seems reasonable.
wildzzz | root | parent
How do you get the salt to make the brine? You'd need to evaporate the water from the brine which means you either need very large evaporation pools or lots of energy to boil the water (and money to maintain the immense amount of scale you create).
dylan604 | root | parent
Build a water desalination plant next door. Make it a twofer
loading story #49736087
lelandbatey | root | parent
You don't need tanks to store the brine, just a huge pit/pool. If you look at satellite imagery, that giant pit with brine in it is exactly what they have next to the storage facilities.
sokka_h2otribe | parent
Hard to find that
mixmastamyk | root | parent
I don't know, the article mentions having to deal with brine. Let it evaporate in a pool and you've got plenty.