The last assessment of undiscovered, conventional oil and gas resources in the world outside the United States was done by the U.S. Geological Survey (USGS) in 2000.

With the latest estimate released April 18, world resources of undiscovered, technically recoverable, conventional resources are estimated at 565 billion barrels of oil; 5,606 trillion cubic feet (Tcf) of natural gas; and 167 billion barrels of natural gas liquids (NGL).

Estimates of oil reserves have gone down since the last World Petroleum Assessment in 2000 while natural gas estimates are higher. In 2000, the USGS estimated conventional resources of 649 billion barrels of oil, 4,669 Tcf of gas, and 207 billion barrels of NGL in 128 geologic provinces.

The new survey covered 171 geologic provinces outside the U.S.  The report includes recent oil and gas assessment of geologic provinces north of the Arctic Circle.  

The assessment includes a complete geologic framework description for each province based mainly on published literature as well as the definition of petroleum systems and assessment units within those systems, according to USGS.
These estimates include resources beneath both onshore and offshore areas. A fact sheet is available. http://pubs.usgs.gov/fs/2012/3042/

All of these numbers represent technically recoverable oil and gas resources, which are those quantities of oil and gas producible using currently available technology and industry practices, regardless of economic or accessibility considerations, noted USGS.

This assessment does not include oil and gas reserves that have been discovered, are well-defined and are considered economically viable.

About 75% of the undiscovered, technically recoverable, conventional oil of the world, exclusive of the United States, is in four regions: South America and the Caribbean (126 billion barrels); sub-Saharan Africa (115 billion barrels); the Middle East and North Africa (111 billion barrels); and the Arctic provinces portion of North America (61 billion barrels).

USGS reports that nearly half of the undiscovered conventional oil resources present in the entire South America-Caribbean Region exists in the areas offshore Brazil.

The geologic provinces of the former Soviet Union, including many Arctic provinces, have estimated mean undiscovered resources of 66 billion barrels of oil.  About 43% of this total are estimated to be in Arctic provinces.  

Gas resources in this region are significant, stated USGS.  The region contains an estimated mean resource of 1,623 Tcf.  About 58% of that total is estimated to be in three Arctic assessment units: South Kara Sea, 622 Tcf; South Barents Basin, 187 Tcf; and North Barents Basin, 127 Tcf.

There is an estimated resource of 941 Tcf in North Africa and the Middle East.  Slightly more than 60% (566 Tcf) of the estimated resource is in the Zagros Fold Belt of Iran, the Red Sea Basin, Levantine Basin and Nile Delta provinces, according to the report.

For North America, exclusive of the U.S., the majority of the undiscovered resources are in the Arctic provinces, including about 75% of the oil (61 billion barrels) and 83% of the natural gas (459 Tcf).

The estimated mean resources for South America are primarily in the basins off the east coast, including: subsalt reservoirs in the Santos, Campos and Espirito Santo basin provinces offshore Brazil, 55.6 billion barrels; Guyana-Suriname Basin, 12 billion barrels; other plays in the Santos Basin, 11 billion barrels; and Falklands, 5.3 billion barrels.

In sub-Saharan Africa, 75% of the estimated oil resources of 115 billion barrels are off West Africa.  Of the undiscovered gas resource mean of 744 Tcf, more than half is estimated to be in the provinces offshore East Africa (Tanzania, Mozambique, Madagascar and Seychelles), USGS said.

“While we continue to focus our efforts on ways to continue to grow domestic energy production for America and further reduce our dependence on foreign oil, better knowledge of untapped resource potential all around the world will help us make better decisions regarding both domestic and global energy policy and resource management,” said Department of the Interior Secretary Ken Salazar.

“In particular, this assessment underscores the importance of continuing to strengthen our energy partnerships in the Western Hemisphere with nations like Brazil, where we are working closely with industry and government to share best practices on offshore drilling safety and to enhance the energy security of both our countries,” he explained.

USGS director Marcia McNutt pointed out, “In the 12 years since the last assessment, the steady progress in technology now allows additional resources to be regarded as technically recoverable.”

These new estimates are for conventional oil and gas resources only. Unconventional oil and gas resources, such as shale gas, tight oil, tight gas, coalbed gas, heavy oil and oil sands, may be significant around the world, but are not included in these numbers.

For example, the mean estimate for recoverable heavy oil from the Orinoco Oil Belt in Venezuela alone is 513 billion barrels, compared to the mean conventional resources of 565 billion barrels for the 171 provinces reported in this study, USGS emphasized.

Contact the author, Scott Weeden, at sweeden@hartenergy.com.