Application of Fast-SAGD in Naturally Fractured Heavy Oil Reservoirs: a Case Study

Steam injection process has been considered for a long time as an effective method to exploit heavy oil resources. Over the last decades, Steam Assisted Gravity Drainage (SAGD) has been proved as one of the best steam injection methods for recovery of unconventional oil resources. Recently, Fast-SAGD, a modification of the SAGD process, makes use of additional single horizontal wells alongside the SAGD well pair to expand the steam chamber laterally. This method uses fewer wells and reduces the operational cost compared to a SAGD operation requiring paired parallel wells one above the other. The efficiency of this new method in naturally fractured reservoir is not well understood. Furthermore, how operational parameters could affect the efficiency of this method is a topic of debate. In this study, Fast-SAGD is compared through numerical reservoir simulations with standard SAGD in an Iranian naturally fractured heavy oil reservoir and additionally some operational parameters including initiating time of steam injection in offset well, number of cycles assuming the same total period of steam injection, offset injection pressure, elevation of offset well from the bottom of reservoir and vertical distance of production and injection SAGD well pairs have been evaluated in Fast-SAGD process. The operational parameters have been optimized based on Recovery Factor (RF) and economical points. The results of this study demonstrated the exceptional performance of Fast-SAGD process in naturally fractured reservoirs and the RFand thermal efficiency of Fast SAGD are enhanced tremendously comparsed to SAGD. In addition, the results indicated that the most important parameters that should be optimized before Fast-SAGD is initiating time of steam injection in offset wells. This study reveals improved efficiency and lower extracting costs for heavy oil in naturally fractured reservoirs applying FastSAGD process. Also it is indicated that optimization of operational parameters significantly improves Fast-SAGD performance in such reservoirs.