A new assessment by the US Geological Survey concludes that expected volumes of undiscovered resources outside the US are 649 billion bbl of oil, 4.67 tcf of gas, and 207 billion bbl of gas liquids, while projected additions to reserves from discovered fields are 612 billion bbl, 3.305 tcf of gas, and 42 billion bbl of gas liquids.
The potential additions to reserves from reserve growth are nearly as large as the estimated undiscovered resource volumes, says USGS, which implies that more than half of the world's "grown conventional oil and gas endowments"�defined as expected reserves additions to existing fields through 2025�have already been discovered in the areas assessed.
"There is still an abundance of oil and gas in the world," said Thomas Ahlbrandt, USGS World Petroleum Assessment project chief. "Since oil became a major energy source about 100 years ago, about 539 billion barrels of oil have been produced outside of the U.S. We now estimate the total amount of future technically recoverable oil, outside the US, to be about 2,120 billion bbl."
Study results
In its recently released World Petroleum Assessment 2000, USGS estimated the quantities of conventional oil, gas, and gas liquids outside the US that could be added to reserves during the 30-year period from 1995 to 2025. A team of more than 40 geoscientists and additional supporting staff conducted the study over a 5-year period from 1995 to 2000.
The assessment is based on extensive geologic studies as opposed to statistical analysis.
"With the evolution of technology and new understandings of petroleum systems, the USGS World Petroleum Assessment 2000 is the first of its kind to provide a rigorous geologic foundation for estimating undiscovered energy resources for the world," said USGS. "The results have important implications for energy prices, policy, security, and the global resource balance."
"These assessments provide a snapshot of current information about the location and abundance of undiscovered oil and gas resources at a point in history," said Gene Whitney, USGS Energy Team Chief Scientist. "Such an overview provides exploration geologists, economists, and investors a general picture of where oil and gas resources are likely to be developed in the future."
The USGS periodically estimates the amount of oil and gas remaining to be found, and since 1981, the last three of these studies have shown a slight increase in the combined volume of identified reserves and undiscovered resources.
The latest study suggests that about 75% of the world's grown conventional oil endowment and 66% of the world's grown conventional natural gas endowment have already been discovered in eight major areas outside the US. In measuring the grown conventional endowments for oil and gas, USGS took into account cumulative production, remaining reserves, the USGS' forecasts for reserve growth for known fields, and undiscovered oil reserves.
Areas assessed in the study include the former Soviet Union, Europe, sub-Saharan Africa and Antarctica, the Middle East and North Africa, North America excluding the US, Asia Pacific, Central and South America, and South Asia.
For these areas, 20% of the world's grown conventional oil endowment and 7% of the world's grown conventional gas endowment had been produced as of the end of 1995. Compared with previous assessments done in 1994 and 1997, the new study pegs undiscovered volumes outside the US as 20% greater for oil, 14% smaller for gas, and 130% greater for gas liquids.
The volume of undiscovered oil estimated in this assessment is greater than the assessment done in 1994, due in part to larger estimates for the Middle East and the Atlantic Ocean off portions of South America and Africa. In some areas�especially Mexico and China�the estimated volumes of undiscovered oil were smaller, notes USGS.
The volume of undiscovered gas estimated in the survey also is smaller than the previous world assessment, mainly because of smaller estimates for Arctic areas such as the former Soviet Union, some basins in China, and the Alberta basin in Canada. The undiscovered volumes of gas liquids are much larger, however, because of more detailed analysis, coupled with the incorporation of coproduct ratios into the assessment calculations.
The areas containing the largest volumes of undiscovered conventional oil include the Middle East, northeast Greenland shelf, the West Siberian and Caspian Sea areas of the former Soviet Union, and the Niger and Congo delta areas of Africa. Significant new undiscovered oil resource potential was identified in a number of areas with no significant production history, such as northeast Greenland and off Suriname.
Areas containing the largest volumes of undiscovered conventional gas include the West Siberia basin, the Barents and Kara Sea shelves of the former Soviet Union, the Middle East, and the Norwegian Sea.
East Siberia and the Northwest Shelf of Australia are two of the areas identified that may contain significant additional undiscovered gas resources where large discoveries have been made but remain undeveloped.
The assessment can be viewed on USGS's website at http://energy.cr.usgs.gov/energy/WorldEnergy/WEnergy.html.
