ABSTRACT
The Brazilian oil and gas E&P sector has been experiencing important changes since the end of the state monopoly in 1998. These changes include a new regulatory environment which is still under construction, in particular the requirements for environmental protection. In this context, Resolution 293 of Brazilian National Environmental Council (CONAMA) was enacted regulating Facility Response Plans for oil spill incidents. These plans, which should be approved by the competent authority, include a vulnerability analysis that should discuss the probability of oil reaching certain areas as well as the environmental sensitivity of these areas. Oil spill modeling is an important tool to estimating the areas likely to be affected by an oil spill. Although oil spill modeling is also part of the environmental studies required in the environmental permitting process for oil E&P activities, there are not well defined criteria to compose the oil spill scenarios to be modeled. In order to demonstrate the impacts of different approaches in the results of oil spill modeling, a case study is presented related to an offshore drilling activity.