The U.S. Geological Survey recently completed an assessment of undiscovered conventional oil and gas resources in 130 selected petroleum provinces of the world (USGS, 2000). Of these 130 provinces, 23 are in South America, Central America, and the Caribbean area (fig. 1). The assessed provinces range from established petroleum provinces with long histories of production such as the Maracaibo Basin to frontier provinces with little or no petroleum production such as the Guyana-Suriname Basin. Not all provinces with historic production or potential production were assessed for the USGS 2000 Assessment. At present we are assessing many of the remaining oil and gas provinces in Central and South America. In each province we (1) geologically defined total petroleum systems, (2) defined assessment units within total petroleum systems, and (3) assessed the volume of undiscovered conventional oil and gas in each assessment unit. We defined 26 total petroleum systems and 55 assessment units in the 23 provinces. The assessment results are summarized in table 1. For the 23 provinces, we assessed mean totals of 105 BBO and 487 TCFG. The South and Central America region ranked third in the world for undiscovered oil and gas behind the Middle East and the Former Soviet Union (USGS, 2000). The potential for giant oil and gas fields is greatest in the provinces along the Atlantic margin of eastern South America, from the Santos Basin in the south to the Guyana-Suriname Basin in the north. The potential for giant fields is mainly offshore, in water depths to 3,600 m. Several giant oil fields have been discovered offshore in the Campos Basin, and similar fields may yet be found in the Campos and adjacent provinces. The provinces along the northern part of South America such as the Maracaibo Basin and the East Venezuela Basin have long been producers of oil and gas, and have been the locations for many giant oil accumulations. The potential for additional giant fields in this suite of provinces is considered to be much less than for the offshore provinces along the eastern margin of South America. However, provinces such as the Maracaibo and East Venezuela (and offshore Trinidad) were assessed to contain significant natural gas resources. In Andean-related provinces, including the Santa Cruz-Tarija, Neuquen, Magallanes, and San Jorge, the potential for undiscovered giant oil fields is low given the geology, exploration maturity, and history of oil discoveries. These provinces have been explored for decades, and the discovery history indicates that smaller oil fields remain to be discovered. However, the potential for large natural gas fields does exist in a few of the Andean provinces.
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U.S. Geological Survey
