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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 littl
by anigbrowl 9d ago
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: https://www.gao.gov/products/gao-26-106918 https://www.gao.gov/products/gao-26-106918
- nxobject 9d agoI also think I've also replied this to you before, but +1 for the GAO report! I use the full report as my personal model yardstick on how I document technical decisions/issues for non-technical people. The PDF is attached here: https://www.gao.gov/assets/gao-26-106918.pdf https://www.gao.gov/assets/gao-26-106918.pdf
- pjc50 9d agoPeople like to be dismissive about civil servants without looking at how much extremely high quality work is actually produced on complex subjects. Personally having interacted with them a couple of times I'm also a fan of the UK Parliamentary briefings: https://commonslibrary.parliament.uk/ https://commonslibrary.parliament.uk/ (unfortunately they can't make people read the briefings ..)
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- noir_lord 9d agoUsual problem, people don't understand what they do so they undervalue what they do or think it is "simple" - almost nothing involving millions of people and their interests is ever "simple". I get somewhat annoyed when people blanket attack Whitehall (the UK Civil Service) universally i.e. the bureaucracy, yes they have problems but you don't run a country with 70 million people without some bureaucracy and ripping apart a system that has worked for centuries means throwing out a lot of good with the "bad".
- FlowingRiver 9d agoIt is funny seeing how the estimates of the lower end stability vary drastically. Have seen numbers between 70 and 150 million barrels. I have just called it half way between that and think 110 million barrels is probably the lowest they should go.
- jordanb 9d agoI think there's a statuary limit at 150 million because there must be an "emergency military reserve" but the caverns start collapsing at 70 million.
- FlowingRiver 9d agoThank you for this, that would explain why difference field are talking different numbers.
- anigbrowl 9d agoThis is the most detailed breakdown of the reserve contents, updated weekly. the sweet/sour differential isn't listed on any other data sources for some reason, and if you want a longitudinal record you'll have to make your own. https://www.spr.doe.gov/dir/dir.html https://www.spr.doe.gov/dir/dir.html
- gruez 9d agoWe can't pump saturated salt solution to prevent more salt from being dissolved?
- sokka_h2otribe 9d agoHard to find that
- mixmastamyk 9d agoI don't know, the article mentions having to deal with brine. Let it evaporate in a pool and you've got plenty.
- smallmancontrov 9d agoSeawater 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 9d agoI disagree that there is no cost associated with making another. Externalising environmental and rectification cost should not be the default approach.
- chabska 9d agoIf 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.
- justinator 9d agoJust spitballing here, can't you just store the salt alone and make the hyper-saturated salt water on the fly? That seems reasonable.
- Morromist 9d agoIt 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?
- greggsy 9d agoThere’s a 3D model of the caverns here https://www.spglobal.com/energy/en/news-research/blog/crude-oil/061516-a-rare-tour-of-the-strategic-petroleum-reserve https://www.spglobal.com/energy/en/news-research/blog/crude-...
- Morromist 8d agoWow 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.
- nostrademons 9d agoThere 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: https://maps.app.goo.gl/B8XJ9TVhQfcdErky5 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.