Impact of Operating Parameters on SAGD Performance in Heavy Oil Naturally Fractured Reservoirs

The application of Steam Assisted Gravity Drainage (SAGD) in fractured reservoirs is in its first stages and needs extensive efforts in order to be applicable in this type of reservoir. In this paper impact of the operating parameters including maximum steam injection rate, well spacing, pressure, preheating period and steam quality on the performance of SAGD is investigated. Based on this study, the injector should be employed at a distance from the producer in order to avoid steam shortcutting and fast communication establishment. An index, Is/Sw (Is: steam injection rate; Sw: well spacing), implicating the steam-oil ratio and efficiency of the process, was introduced. It is found that there is an optimum injection rate for each well spacing. While preheating is an essential part of SAGD in sandstone, the process can be initiated without preheating, although it can facilitate the start-up phase in some conditions. Finally, it is found that steam quality plays an important role in process performance since it not only increases the latent heat delivered to bitumen but also increases the gravity difference between oil in the matrix and steam in fracture, leading to higher oil recovery when the steam quality is higher.