This pipe appears to be a possible vent for a buried oil tank, but I seriously doubt it, because the pipe is plastic, and the home was built in 1971. It is also right next to the home.
Any ideas what this may be? Only other thing I could think is a possible plumbing vent.
I did not take a better pic of the top like I should have to try and read it… 
The cap does look like that of an oil vent, however, the rest of it does not look like a typical vent pipe used for an oil tank. The vent pipe is required to be at least 1 1/4" and on very old tanks it could be as small as 1" What you have in the picture looks like 1" and plastic? So not really sure, possibly some home-brew thing. Were there any other signs of oil conversion? old chimney? old oil supply lines? is the area known to have oil systems?
Exactly why I was confused. It does look like an oil vent cap. But no, there were no other indications…no chimney, no lines, the home is all electric (as most homes here are), and I have only seen signs of an oil tank twice in the 3 years I have lived here.
Thx