USGS World Petroleum Assessment and the Total Petroleum System (TPS)

The U.S. Geological Survey (USGS) World Petroleum Assessment 2000 provides
estimates of the quantities of conventional oil, gas, and natural gas liquids
outside the United States that have the potential to be added to reserves in
the next 30 years (1995 to 2025). Excluding the U.S., the mean (expected)
volumes of undiscovered resources are 649 billion barrels of oil (BBO), 4,669
trillion cubic feet of gas (TCFG), and 207 billion barrels of natural gas
liquids (BBNGL).

This assessment is based on extensive geologic studies as opposed to
statistical analysis. A team of more than 40 geoscientists and additional
supporting staff conducted the study over a five-year period from 1995 to 2000.
The petroleum assessed occurs in fields exceeding a stated minimum size, which
varies between 1 and 20 million barrels of oil equivalent in different areas,
and in accumulation categories judged to be viable in a 30-year forecast span.

The critical geologic controls on petroleum distribution are encompassed by the
Total Petroleum System (TPS) and were studied using this approach. Assessment
Units (AU), within the TPS, were the basic units for assessment. Overall, 159
TPS and 270 AU were identified in 96 countries and 2 jointly held areas. Of
these, 149
TPS and 246 AU in 128 geologic provinces were quantitatively assessed. The
assessed areas were those judged to be significant on a world scale in terms of
known petroleum volumes, geologic potential for new petroleum discoveries, and
political or societal importance. In the course of our geologic analyses, 24 AU
were identified as containing continuous (nonconventional) resources, but these
were not quantitatively assessed.

For each AU, allocations of undiscovered resources were made to the countries,
geologic provinces, regions, and offshore areas (if any) involved. From these
allocated portions, aggregations of estimates were made for higher levels such
as to countries, geologic provinces, and groups of countries including the
Organization of the Petroleum Exporting Countries (OPEC) and the Organization
for Economic Co-operation and Development (OECD).

The United States was not reassessed in this study; estimates previously made
by the USGS in 1995 and the Minerals Management Service in 1996 were used for
comparative purposes.

To access the data and assessments, see "http://pubs.usgs.gov/dds/dds-060/"