The U.S. Geological Survey (USGS) recently assessed potential volumes of undiscovered technically recoverable conventional oil, natural gas, and natural gas liquids (NGL) of the world, exclusive of the United States (USGS, 2000). Using a geology based methodology, the USGS defined 149 total petroleum systems (TPS) and 246 assessment units (AU) in 128 oil and natural gas provinces worldwide, and quantitatively assessed undiscovered resources in each of the 246 AU. This assessment provides estimates of the quantities of conventional, technically recoverable oil, natural gas, and natural gas liquids, exclusive of the United States, that have the potential to be added to reserves in the next 30 yr (1995 to 2025). These amounts include estimates of undiscovered volumes and the estimated volume of reserve growth for discovered fields. The assessment results are shown in Table 1, and are summarized as follows: a mean of 649 billion bbl of undiscovered conventional oil with a range of 344–1107 billion bbl of oil; a mean of 4669 tcf of conventional natural gas with a range of 2299–8174 tcf, and a mean of 207 billion bbl of natural gas liquids with a range of 95–378 billion bbl of NGL, exclusive of resources in the United States. Adding these assessment results to estimates of undiscovered oil and natural gas resources of the United States, the cumulative production, remaining reserves, and reserve growth of provinces throughout the world, a total world endowment of conventional oil resource, was estimated by the USGS to be about 3 trillion barrels
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Presented in this publication are the results of a major study of the petroleum resources of the world as analyzed by total petroleum systems. The distribution and volumes of resources available in these systems are critically important for the future of the world's economies.Â Geologic insights gained from studying these 149 systems and their constituent assessment units in 128 provinces and 96 countries, exclusive of the United States, allow a new look at petroleum accumulations and the rocks that are intimately associated with them. The geographic distributions of oil and natural gas systems show significant differences. Lists of new areas of potential and new estimates of resources make this a must-have addition to the petroleum geologist's library.