Oil spill analysis and simulations in the Foz do Amazonas sedimentary basin

One of Petrobras' main exploration fronts until 2028 is the Brazilian Equatorial Margin, where 16 wells are scheduled to be drilled. Within this area, the Foz do Amazonas Sedimentary Basin (SFZA) stands out, covering the coast of Amapá and part of Pará. In this region, Petrobras is seeking environmental licenses to drill six already acquired blocks, while several others are up for sale by the ANP (National Agency of Petroleum, Natural Gas, and Biofuels). Initially, the company conducted oil spill simulations suggesting that spilled oil would not reach the Brazilian coast due to the strong influence of the North Brazil Current (NBC), which would carry it northwest toward Central America. However, for a more in-depth analysis, we used the MEDSLIK-II model to conduct new simulations, both in Petrobras' area of interest and in other locations proposed for auction. The results obtained with MEDSLIK-II align with Petrobras' previous simulations for the summer and winter periods. However, during the boreal spring, oil reached the coasts of neighboring countries. For other blocks for sale located southeast in the SFZA, the risk of oil reaching the Brazilian coast and neighboring countries is significantly high, especially from boreal autumn to late spring. Given this new evidence, it is essential to conduct more detailed studies before authorizing any drilling in the region. It is also advisable to reassess the sale of new blocks until the risks are better understood. • Oil spill risk evaluated for exploratory blocks in the Amazon margin; • Independent assessment complements Petrobras environmental studies; • Results support improved environmental risk assessment frameworks.