USGS GLOBAL 2000 ASSESSMENT SHOWS INCREASED OIL POTENTIAL

The United States Geological Survey (USGS), in its 2000 World Assessment, estimates world undiscovered, conventionally recoverable resources of oil, natural gas and natural gas liquids at 1,634 billion barrels of oil equivalent (boe) in 2000, excluding the United States. This is about 5 percent higher than the USGS 1994 estimate of 1,556 billion boe. The new report covers the period 1996-2025 and for the first time includes an estimate of the potential from field growth.

In USGS World Petroleum Assessment 2000, the world was divided into approximately 1,000 petroleum provinces, based primarily on geologic factors, and then grouped into eight regions roughly comparable to the eight economic regions defined by the United States State Department. Significant petroleum resources are known to exist in 406 of the 1,000 geologic provinces. The USGS estimates for the eight main areas are summarized in Table 1.

Table 1

The oil resource estimate increased from the 1994 assessment by 20 percent. Gas declined by 10 percent and natural gas liquids jumped by 130 percent. With 1995-1996 estimates for the United States added to the new numbers, the total undiscovered resource increases from 1.65 trillion boe to 1.807 trillion boe from the prior estimate, with oil up 24 percent, gas down 10 percent and natural gas liquids up 104 percent.

USGS puts the most likely estimate for undiscovered oil outside the United States at 649 billion barrels and for field growth at 612 billion barrels. For gas the estimates are 778 billion boe (4.669 quadrillion cubic feet) of undiscovered resource and 551 billion boe (3.305 quadrillion cubic feet) for field growth.

The addition of the field-growth estimates acknowledges the great amounts of oil and gas that producers have added to reserves through knowledge about previously discovered reservoirs and through technology. Specifically:

• As drilling and production within discovered fields progresses, new pools or reservoirs are found that were not previously known.
• Advances in exploration technology make it possible to identify new targets within existing fields.
• Advances in drilling technology make it possible to recover oil and gas not previously considered recoverable in the initial reserve estimates.
• Enhanced oil recovery techniques increase the recovery factor for oil and thereby increase the reserves within existing fields.

Advancing knowledge also accounts for gains in undiscovered resources. The largest increases are in the Middle East and North Africa and off South America and Western Africa. The Middle East and North Africa increases, USGS says, reflect new understanding of resource size in Jurassic and Cretaceous petroleum systems. Gains in the Southern Atlantic come from deepwater, turbidite reservoirs made accessible by new technology.

Estimates declined for resources in Mexico and China because of new information previously unavailable to USGS. Most of the drop in the gas-resource estimate occurred in arctic areas of the former Soviet Union. There also were declines in Chinese and Canadian provinces.

USGS estimates the ultimately recoverable conventional oil resource outside the United States at 2.659 trillion barrels (see Table 2). It puts the ultimately recoverable, non-United States gas resource at 13.493 quadrillion cubic feet.

Table 2

The new estimates mean that much exploration and development remain to be done. And growth in the oil numbers from the former USGS estimate shows that the relevant constraint on future supply at this point in history is what people know about the subsurface, not how much oil and gas nature put there.