A very worthwhile study. Don't have time to work on this right now, but I think it would be very helpful to put in date of discovery and recent production stats. Most important right now is not just original reserves but the production they contribute currently. For example, China's largest field Daqing is not on the list but should be, and it peaked in 2003, I believe.

http://www.chinagate.com.cn/english/208.htm
http://www.chinadaily.com.cn/en/doc/2004-01/06/content_296195.htm

Looks like Daqing dropped below 1 mbpd starting in 2003-2004 after decades of production over that figure.