Estudo do aquecimento geral indireto como método de recuperação em reservatórios rasos de óleos pesados

Abstract

Due to the reduction in world light and medium oil reserves, heavy oil started to attract researches and investments that seek its extraction with minimal costs and minimal environmental damages. The main recovery method worldwide applied for heavy oil recovery is the steam injection. Blanket Heating is a technique that uses the steam injection through horizontal conduits where the heated fluid functions as a heat exchanger, with indirect steam heat transfer to the oil, without mass transfer between steam and reservoir fluids, in order to reduce its viscosity and avoiding the direct introduction of steam in the formation. The use of this new process, in reservoirs for depths between 50 m and 200 m (where the vast majority of heavy oil is found) has been examined. Aiming at testing the applicability of this method in shallow reservoirs with distinct characteristics, and comparing it with the traditional process of continuous steam injection, computer simulations were conducted. The study, carried out in a commercial simulator - STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator) from CMG (Computer Modeling Group), tested the efficiency of the method in relation to changes in reservoir parameters and selected three formations whose specifications were classified as the best, the worst and the intermediate oil recovery cases, indicating which configuration of operational parameters resulted in maximum recovery in each of the three selected reservoirs. The choice of the horizontal direction reflects the need to maintain the greatest possible contact area between conduits and oil reserves. The results showed that the recovery can be maximized in proportion to the increase of temperature in the conduits and to the number of conduits. Cumulative oil is reduced when the distance between the conduits and production wells or between the pipes is greater. The study showed that blanket heating does not produce significant emissions of steam to the surface area, confirming the reduction in the amount of produced water. Finally, the analysis of statistical data pointed to the better performance of the blanket heating method in shallow reservoirs, in comparison with the continuous steam injection, taking into account several factors such as the oil/water cumulative production.