This paper presents an analysis of capacity aspects of offshore helicopter traffic in Southeast Brazil, in the region called Campos Basin, which is the main sedimentary area explored for oil & gas off the Brazilian coast. The ADS-B technology (Automatic Dependent Surveillance Broadcast) is being implemented in the region by the Department of Airspace Control (DECEA), to improve surveillance and reduce traffic separation, while maintaining a high level of safety. The main oil companies use the service of offshore helicopter transportation for their employees to reach the oil platforms and vessels, located far away from coast. Hermeto [1] presented that the airport network consists of four main airports on land that serves the Campos Basin, and the traffic in these airports is intense. Petrobras, the major oil company in Brazil, demands about 100,000 flights per year at Campos Basin. It is estimated that the demand for air transportation will double over the next years with oil exploration under pre-salt layer [2]. This paper presents an estimation of the new traffic capacity with implementation of ADS-B technology. Using a fast-time simulation model based on real flight data, it was possible to simulate different scenarios of operation, including Visual Flight Rules (VFR) and Instrument Flight Rules (IFR), and with them estimate the new air traffic capacity. Critical situations occur due to adverse weather, after which an amount of lag days with normal weather is needed to return to steady-state operation. This is an indication that this transportation system needs more robustness against perturbations. Our simulations show that the use of ADS-B technology provides an increase of about 50% in the theoretical capacity of the Campos Basin airspace; and for the current demand, this improvement helps the prevention of around 60 flight cancellations in a day with IFR operations prevailing.