World resource estimate shows more liquids, slightly less gas

April 17, 2000
The world's endowment of conventional oil remains on the rise, according to a comprehensive study being released this spring by the US Geological Survey.
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The world's endowment of conventional oil remains on the rise, according to a comprehensive study being released this spring by the US Geological Survey.

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The USGS, in its 2000 World Assessment, estimates world undiscovered, conventionally-recoverable resources of oil, natural gas, and natural gas liquids at 1,634 billion bbl of oil equivalent in 2000, excluding the US. This is about 5% higher than the USGS 1994 estimate of 1,556 billion boe.

The 2000 assessment reflects a 20% increase in estimate of undiscovered oil, a 130% hike in NGL, and a 14% decline in undiscovered gas.

Including US undiscovered estimates, the current assessment is up 9.5% overall, and the individual changes are oil up 24%, NGL up 104%, and gas down 10%.

The assessment is an estimate of the volume of oil and gas, excluding the US, that may be added to the world's reserves in the next 30 years (OGJ, Apr. 10, 2000, p. 25).

Several "firsts" were incorporated into the latest assessment, USGS said.

What the data show

USGS divided the world into about 1,000 petroleum provinces based mainly on geologic factors and grouped them under eight economic regions. Significant petroleum resources are known to exist in 406 of the 1,000 provinces.

Here are the USGS estimates for the eight main areas:

Middle East and North Africa 230 billion bbl undiscovered (35.4% of world total) and 1,370 tcf of gas undiscovered (29.3% of world total).

Former Soviet Union 116 billion bbl (17.9%) and 1,611 tcf (34.5).

Central and South America 105 billion bbl (16.2%) and 487 tcf (10.4%).

Sub-Saharan Africa and Antarctica 72 billion bbl (11%) and 235 tcf (5%).

North America (excluding US) 70 billion bbl (10.9%) and 155 tcf (3.3%).

Asia-Pacific 30 billion bbl (4.6%) and 379 tcf (8.1%).

Europe 22 billion bbl (3.4%) and 312 tcf (6.7%).

South Asia 4 billion bbl (.6%) and 120 tcf (2.6%).

The resource estimates have implications for energy prices, policy, security, and the global resource balance.

The overview also provides exploration geologists, economists, and investors a general picture of where oil and gas resources are likely to be developed in the future, said Gene Whitney, USGS energy team chief scientist.

Key points, changes

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USGS for the first time estimated reserve growth potential at the world level.

The estimates of reserve growth outside the US are 612 billion bbl of oil, 3,305 tcf of gas, and 42 billion bbl of NGL.

Although not estimated at the regional level, this potential is significant in that combined it is nearly as large as the undiscovered resource estimates.

Reserve growth can result from discovery of new pools or reservoirs in known fields, exploration and drilling technology advances, and the application of enhanced oil recovery techniques.

Compared with the prior estimate, the 2000 study indicates more oil and gas in the Middle East and North Africa and off western Africa and eastern South America, less oil and gas in Canada, Mexico, and China, and significantly less gas in the Former Soviet Union, especially the arctic.

Thomas Ahlbrandt, USGS world petroleum assessment project chief, said world cumulative production outside the US is about 539 billion bbl since oil became a major energy source about 100 years ago.

"We now estimate the total amount of future technically recoverable oil, outside the U.S., to be about 2,120 billion bbl." That figure includes reserves.

The full study is to be released at the World Petroleum Congress in Calgary in June. Supporting geological data have already been released for the Former Soviet Union; Sub-Saharan Africa and North Africa; the Arabian Peninsula; South Asia; the Asia-Pacific Region; South America; and Iran.

Assessment firsts

The USGS noted that the 2000 assessment is the first in which:

  • Total Petroleum System and its constituent Assessment Units are used rather than plays, basins, or countries.
  • USGS considered world-level field growth.
  • The estimates are limited to a time frame (1996-2025) that recognizes technology and financial aspects.
  • Every aspect of the assessment is digitally documented. USGS anticipates as many as four CD-Roms to hold all of the aggregated data.
  • Methodology uses a truncated shifted lognormal distribution for undiscovered field size distributions.

The USGS has conducted increasingly sophisticated resource estimates every few years since 1981. The last three efforts showed slight increases in the combined volume of identified reserves and undiscovered resources.