Is there or was there a pool close to this pipe?
I had a friend that put in pools down there, and he would dig a short (well) like the one you are talking about.
It was used to de-water the ground while the pool was excavated.
Most of the time the pipe was pulled back out of the ground to use for the next pool.
The home owner may have ask to keep the pipe there, to try and do the same thing you are trying to do.
That may be what you have.
Just a thought I had.