The U.S. Geological Survey (USGS) assessed the potential for undiscovered conven-tional oil and gas fields within priority geologic provinces of South America and the Caribbean as part of the USGS World Petroleum Resources Project (fig. 1). Thirty-one geologic provinces were assessed in this study, which represents a complete re-assessment of the South America−Caribbean region published in 2000 (U.S. Geological Survey World Energy Assessment Team, 2000).

The methodology for the assessment included a complete geologic framework description for each province based mainly on published literature and definition of petroleum systems and assessment units (AU) within these systems. Exploration and discovery his-tory was a critical part of the methodology to determine sizes and numbers of undiscovered accumulations. In those AUs with few or no discoveries, geologic and production analogs were used to estimate sizes and numbers of undiscovered oil and gas accumulations. Each assessment unit was assessed for undiscovered oil and nonassociated gas accumulations, and co-product ratios were used to calculate the volumes of associated gas (gas in oil fields) and volumes of natural gas liquids. This assess-ment is for conventional oil and gas resources only; unconventional resource assessments (shale gas, shale oil, tight gas) for this region are being completed in a separate study.

The provinces assessed in this study represent a wide range of tectonic settings and evolution, stratigraphic fill, thermal evolution, petroleum systems, and exploration his-tory. There are many provinces in this region that have been maturely explored, such as Maracaibo Basin, Neuquen Basin, Magallanes Basin, and Llanos Basin, whereas several provinces have few or no discover-ies, such as Salado-Punta del Este, Parnaiba, and Bahama Platform. The range of resource estimates for each province reflects the geologic uncertainty