Year-end proved reserves in 2007 stood at 21.3 billion barrels, nearly 2 percent higher than at the end of 2006.
The largest increase of year-end crude oil proved reserves came from Alaska, growing 7 percent over 2006 (284 million barrels), followed closely by Texas with a year-end increase in proved reserves of 5 percent (251 million barrels). Alaska's increase included 45 million barrels of new field discoveries.
Due to rapid development of unconventional oil resources associated with the Bakken Formation, North Dakota had the third largest year-end increase in crude oil proved reserves, up 17 percent from 2006 (70 million barrels).
More info: http://www.eia.doe.gov/oil_gas/fwd/adsum.html