DANGER
I don't want to alarm you, but these things can be very dangerous if not plugged correctly.
H2S (hydrogen sulfide) is a deadly gas that can come from the well. My brother in law had a near-miss with a well on his property, he stumbled away from the well, luckily his wife saw him and luckily the wind picked up. I've known lots of guys who've been in similar situations on location.
Post a picture from a distance and up wind if you can. Depending on how comfortable you are, you can buy an H2S meter and walk over to it. The meters are cheap.
* Is the well caped on surface?
* Is casing cut below ground level?
* Is the location fully remediated?
* Does the work look good? Are pipes corroded?
Picture is worth a thousand words.