What does the finish on the outside look like? You could take the door out, trim the jamb to fit the 2x4 wall, and rehang it.

They weren’t fooling around. But, bare wood against concrete may start to rot. If your foundation isn’t damp-proofed and we’ll drained.

Are the spaces 24” or are the studs 24” on centre? You should be able to find fibreglass batts that work for 24 on centre.

As far as the depth of the studs goes, can you move the framing out? Pull the nails top and bottom and move it out from the wall 3”. That'll give you plenty of room for insulation. I'm assuming that the framing isn’t structural—just backing for drywall.

What counts as an oilfield? Google says the Permian Basin produces 5 Mbpd.