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The engineering behind the US Strategic Petroleum Reserve

67 points by johnjwang 2 days ago | 11 comments

anigbrowl 45 minutes 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

nxobject 26 minutes ago

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:

https://www.gao.gov/assets/gao-26-106918.pdf

Ellis_dev 56 minutes ago

Makes you appreciate the physical infrastructure challenges, not just software. Bet the data logging and monitoring systems are ancient but robust.

bt1a 42 minutes ago

Yea man the federal government is on top of protecting civilian groundwater supplies and communicating discoveries of contamination

analog31 55 minutes ago

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.

metrix 23 minutes ago

What do they do with the brine when they fill it back up with oil?

And do they use fresh water?

ivraatiems 38 minutes ago

How long does the crude last uner these conditions? Refined oil products like gas have pretty limited shelf lives (I think 6-12 months for gas).

aqfamnzc 34 minutes ago

Under ideal conditions - about 200 million years at least. In the salt, I'm not sure.

buckle8017 36 minutes ago

well it's been underground in similar conditions for a couple dozen million years, so I think a while

hankbond 2 hours ago

Very cool, big fan of these bite size explainers. Has there been more cycling recently? Are the sizes of the caverns tracked anywhere?

bt1a 40 minutes ago

id imagine if you have the location of a site that the largest pipes visible from satellite photography would be consistently scaled in some manner with the tank size. this is guess