[thackney]

There are a number of old oil fields which serve in some capacity as storage for the US Strategic Petroleum Reserve.

All of the US Strategic Petroleum Reserve are salt dome caverns. They are man-made caverns in salt domes. There are multiple caverns at each of the four sites.

The connections to each cavern are made above ground at a wellhead. The facilities are then connected to multiple pipelines and loading docks.

http://energy.gov/fe/services/petroleum-reserves/strategic-petroleum-reserve/spr-storage-sites

[bestintxas]

Yep, and those salt domes has oil somewhere on their flanks.

The areas used for SPR were leached out with fresh water to create cavities