The Brazilian Pre-Salt region has garnered much attention since the first major discoveries were announced by Petrobras, in 2006. Since then, discoveries in the region have ranked among the largest in the world in the last ten years, including Lula (former Tupi), Iara, and Libra. This led to various estimates, from within and outside the government, that mentioned extremely large total possible accumulations, ranging from 50 to over 300 billion barrels of recoverable oil in the "Picanha Azul" region, an area of approximately 150 thousand square kilometers. Since none of these estimates was accompanied by technical data, or a description of the methodology used, an assessment of the potential for yet-to-find oil was carried out using a software tool which models the exploration process, making Monte Carlo simulations based on the information available regarding wells drilled, discoveries made, respective dates, and the areas involved. The assessment methodology used has been successfully applied by the authors in evaluating the potential of other areas, such as the shallow waters of the Campos Basin. While the present Pre-Salt region assessment does not have as many information points available as in those prior assessments, the intense exploration activity has resulted in enough information being available about the region so as to be able conduct an assessment over the entire area. Applying the concepts of discovery sequence and field size distribution, and making geological estimates for parameters of the number and size of accumulations, the current assessment furnished a probability distribution for the number and expected size of individual accumulations (fields) yet to be discovered, as well as for the total accumulation of yet-to-find recoverable oil in the region. The relatively large range of possible values of the results reflects the lack of more exploratory experience (discoveries or dry wells), which will only come about with time, despite the intense exploratory efforts currently under way. Even so, it was possible to suggest that within probabilistic confidence levels of 95% and 5%, field sizes expected will range from 165 million barrels to eight billion barrels, and total accumulations will range from 115 billion barrels to over 288 billion barrels.

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