Just found out that the house we recently purchased has an open shaft (hand dug I suspect) well smack dab in the middle of my crawl space. Evidently it has been there since the 1930's when the original home was added on to.
Can I just cover it (seal it) and forget it?
Don't know how deep or diameter of it yet but that is on my list of things to find out.
Sounds like it might not be a well but an old cistern. If so, and it is more or less structurally intact, you can probably leave it alone so long as you seal it off at the top for safety reasons (pets, kids, etc. falling down into it). The best thing would be to fill it in though.
If it really is a well, it will have to be destroyed (filled in) properly to prevent polluting the groung water. Check with a reputable well driller in your area, as filling it in might not be allowed as DIY. A cistern can probably just be filled in, but again a driller in your area will know for sure.