How does a well fall in?
Ernest, please read this stark assessment/ possible scenario that was posted here on FR earlier today, that answer is contained herein:
http://www.theoildrum.com/node/6593/648967
Usually, they collapse, but not in the sense they leave a crater. Formations spall downhole and fill the hole or flow (like salts) and pinch the casing off. Most people don’t realize that by the time a well like this gets to total depth, it is usually somewhere between six inches to a foot in diameter, unlike old surface water wells a kid seems to find every couple of years.