Published Estimates of World Oil Ultimate Recovery
1. This graph shows many estimates of world oil resources made since 1942. They have ranged from 600 billion to 3,896 billion barrels.
2. There is an overall increasing trend of ultimate recovery estimates over time. This trend is primarily due to increases in the quantity and quality of geological, geophysical, and reservoir engineering information, and to the development of more rigorous estimation methodologies.
3. For example, by 1959 Weeks' estimate had tripled from his 1948 estimate of 600 billion barrels to 2,000 billion barrels. The same kind of increase is observed in other cases in which the same estimators made successively larger estimates.
4. The largest world oil ultimate recovery estimates are the newly released USGS estimates. The USGS 95 percent probable value is 2,248 billion barrels (meaning there is a 19 out of 20 chance that the value will be greater than 2,248 billion barrels). Similarly, the USGS says there is a 5 percent probability (1 chance out of 20) that the value will exceed 3,896 billion barrels. The USGS mean estimate (the expected value) is 3,003 billion barrels.
5. There are a number of basins, especially in the Arctic and Antarctica, that were not included in the USGS world resource assessment because they were judged unlikely to add proved reserves during the next 30 years. Therefore, there is still some potential for even higher resource assessments.