<P> The United States Geological Survey (USGS) estimates undiscovered technically recoverable crude oil onshore in United States to be 48.5 billion barrels (7.71 × 10 ^ m) The last comprehensive National Assessment was completed in 1995 . Since 2000 the USGS has been re-assessing basins of the U.S. that are considered to be priorities for oil and gas resources . Since 2000, the USGS has re-assessed 22 priority basins, and has plans to re-assess 10 more basins . These 32 basins represent about 97% of the discovered and undiscovered oil and gas resources of the United States . The three areas considered to hold the most amount of oil are the coastal plain (1002) area of ANWR, the National Petroleum Reserve of Alaska, and the Bakken Formation . </P> <P> The Minerals Management Service (MMS) estimates the Federal Outer Continental Shelf (OCS) contains between 66.6 and 115.1 billion barrels (10.59 × 10 ^ and 18.30 × 10 ^ m) of undiscovered technically recoverable crude oil, with a mean estimate of 85.9 billion barrels (13.66 × 10 ^ m). The Gulf of Mexico OCS ranks first with a mean estimate of 44.9 billion barrels (7.14 × 10 ^ m), followed by Alaska OCS with 38.8 billion barrels (6.17 × 10 ^ m). At $80 / bbl crude prices, the MMS estimates that 70 billion barrels (11 × 10 ^ m) are economically recoverable . As of 2008, a total of about 574 million acres (2,320,000 km) of the OCS are off - limits to leasing and development . The moratoria and presidential withdrawal cover about 85 percent of OCS area offshore the lower 48 states . The MMS estimates that the resources in OCS areas currently off limits to leasing and development total 17.8 billion barrels (2.83 × 10 ^ m) (mean estimate). </P> <P> In 1998, the USGS estimated that the 1002 area of the Arctic National Wildlife Refuge contains a total of between 5.7 and 16.0 billion barrels (2.54 × 10 m) of undiscovered, technically recoverable oil, with a mean estimate of 10.4 billion barrels (1.65 × 10 m), of which 7.7 billion barrels (1.22 × 10 m) falls within the Federal portion of the ANWR 1002 Area . In May 2008 the EIA used this assessment to estimate the potential cumulative production of the 1002 area of ANWR to be a maximum of 4.3 billion barrels (680,000,000 m) from 2018 to 2030 . This estimate is a best case scenario of technically recoverable oil during the area's primary production years if legislation were passed in 2008 to allow drilling . </P> <P> A 2002 assessment concluded that the National Petroleum Reserve--Alaska contains between 6.7 and 15.0 billion barrels (2.38 × 10 m) of oil, with a mean (expected) value of 10.6 billion barrels (1.69 × 10 m). The quantity of undiscovered oil beneath Federal lands (excluding State and Native areas) is estimated to range between 5.9 and 13.2 BBO, with a mean value of 9.3 BBO . Most oil accumulations are expected to be of moderate size, on the order of 30 to 250 million barrels (40,000,000 m) each . Large accumulations like the Prudhoe Bay oil field (whose ultimate recovery is approximately 13 billion barrels (2.1 × 10 m)), are not expected to occur . The volumes of undiscovered, technically recoverable oil estimated for NPRA are similar to the volumes estimated for ANWR . However, because of differences in accumulation sizes (the ANWR study area is estimated to contain more accumulations in larger size classes) and differences in assessment area (the NPRA study area is more than 12 times larger than the ANWR study area), economically recoverable resources are different at low oil prices . But at market prices above $40 per barrel, estimates of economically recoverable oil for NPRA are similar to ANWR . </P>

What percentage of the world's oil reserves is found in the united states