The main goal of this dissertation is to improve the usage of Petrobras' crude oil and oil products short sea fleet through a new cost model and an operation decision tool regarding its refueling activities. Currently, it is common practice to deviate the ships from their transportation route to refuel, given the lack of refueling structure in 59 of the 73 ports and platforms in which the short sea fleet operates. Until this moment, the refueling decision wasn't supported by any tool and there was little transparency regarding the cost impact to the decision makers. This action research is conducted within the context of practice of the ship operations and ship scheduling areas. This works' contributions include a refueling cost model, that is later unfolded in a technological product that includes a Decision Support Tool that helps to decide when and which Fuel Oil quantity to refuel. The dissertation also designs a standardized decision flow, that results in a 14,8 million Reais yearly saving potential when applied to the 2017 routes, no investment needed. To verify the adhesion of the proposed flow, 6.318 port calls made by 114 vessels were analysed. Despite the larger number of refueling operations and total fuel quantity proposed, the cost reduction is verified due to the elimination of the port calls made exclusively for refueling. If the option is made to enable refueling activity in the port of Suape, it is possible to further increase the yearly savings in at least 4 million Reais.