Actually the information is easily available so next time I am just gonna tell you to do your own homework. But here is a hint!
G-O-O-G-L-E ... S-E-A-R-C-H
Check into it, ok?
That being said, apparently there are about 400,000 capped wells in the US.
Here is an excerpt...
"It will also give new life to the capped wells in the U.S., which number approximately 400,000. Just think about the possibilities: there is an estimated 40 years of oil in capped wells in the U.S. at 21,000,000 barrels a day in usage."
And for being such a smartazz I'm gonna make you block and copy. No handy links for you!
http://findarticles.com/p/articles/mi_m5CNK/is_2006_Dec_4/ai_n24996550
http://www.npr.org/templates/story/story.php?storyId=5147602
http://www.presstelegram.com/business/ci_8672275
Shale oil deposits. These were not producing oilwells to begin with. Conventional wells are not “capped” they are “plugged”.