Its not like any well I've ever seen. Could the square thing on the right be a shut-off valve and could it have been fed by water from the house? You may have to dig down along side the pipes to find that answer. Anything in your basement that suggests there's water piping heading that direction?

Don't look like a well head to me either, but then the ones around here usually have caps on them, have electrical bits, and are for houses. It does look like a water thing though- like a hose would connect to the threaded pipe, and the square thing looks like you could use a wrench to turn the water on/off.

Maybe it was for a sprinkler system or water feature at one point? Pond or pool filler? What else is in that area of the yard?

How close to the house is it? And/or is it near your driveway?