The perspectives in the rise of the national production of petrol, after the recent discoveries of the pre - salt pole and consequently the rise in the number of points of drainage via maritime modal have been turning the logistics systems of supplements of the national refineries and the exports of the exceeding volumes more and more complex. Further more one must consider the curve in the production of water that rises along with the production in a living reservoir of petrol influencing in its quality. Taking this context into consideration it is notorious that it is needed to create a process of managing stocks that is able to define its ideal levels , forecast the stocks and the quality of storied oil, as well as suggesting its withdrawal to support the process of decision making related to the programming of ships for the flow of production so as to guaranty its continuity regarding the specifications of quality required besides considering the analysis of its trade off between the costs of maritime transport and the cost of the opportunity of stored oil. This paper presents the developing and the beginning of the implementation of a managing process of stock in the area of upstream of an integrated company in the gas and petrol segment where there was the necessity of development of a simulator to preview the quality and the stock in maritime unities in the flow of petrol. To begin with most of the variables of entry in the model will be determining but it is recommended that in the future all the other variables are incorporated so as the simulator is able to capture the stockiest nature of the process and its complexity.