Commenters elaborate on how salt caverns actually contain oil
2 Sep 16 7:35 PM · 7d ago · 1 post · 8 comments · 2 sources · development 2 of 3
HN users anigbrowl and nostrademons add detail beyond the article on why salt's low permeability and plasticity let it hold oil without a steel lining, and describe how operators presaturate injection water with salt to stop the caverns from dissolving further.
“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.”
anigbrowljohnjwang Author of the engineering explainerU.S. Navy Operator of the Red Hill fuel storage facilityanigbrowl HN commenternostrademons HN commentertmellon2 HN commenter
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What people said 10 voices · verbatim
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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 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…
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I 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:
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I’m certain engineers have considered this, but it doesn’t seem answered anywhere: why not just pump the original brine back in to move around the oil? Wouldn’t that at least prevent eroding the storage unit and causing it to fail?Unrelated: dang, he wasn’t underselling this being a pretty elegant solution! I never would’ve thought of it, for sure.
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An interesting aside is that the process for making these salt domes is also used for mining salt. Drill a hole, pump water down, and up comes brine. The brine can be used as a chemical feedstock, e.g., for production of things like chlorine, sodium hydroxide (lye), and sodium carbonate for glass.
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One thing about salt domes: they almost by definition are surrounded by very low-permeability dry soils. Because otherwise they would have dissolved long ago!And a related way to use salt domes is for natural gas storage.
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One fun fact I’ve heard is that the strategic oil reserve requires like 100-150 million barrels of oil to maintain operational pressure and even be functional. This means we can’t draw it down to zero; not even close.
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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?
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Makes you appreciate the physical infrastructure challenges, not just software. Bet the data logging and monitoring systems are ancient but robust.
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Very cool, big fan of these bite size explainers. Has there been more cycling recently? Are the sizes of the caverns tracked anywhere?
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We can't pump saturated salt solution to prevent more salt from being dissolved?
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