Perpustakaan Digital ITB

Due to the increasing demand of oil production in Indonesia, various strategies are being implemented to suffice the target. With majority of the fields in Indonesia are being considered as old and are in their declining stage of production, one of the most promising strategy to do is to improve our means and applications on Enhanced Oil Recovery or EOR. One of the most widely used method of EOR is gas injection method. Gas injection has been attributed to contact of the unswept zones, making contact and increasing the mobility of the residual oil in the reservoir. This study focuses to improve the oil production at “B” structure of “S” field located in South Sumatra, Indonesia, which is already in a declining stage of production. A significant amount of hydrocarbon gas is produced continually in this field and is currently being used as a flare. The improvement of oil recovery by using gas injection will then be investigated further in this field to utilize this resource. However, there are also some challenges of injecting gas continuously. Hence, the gas injection method is proposed to be injected alternatively with water to improve its sweeping efficiency. This technique is known as Water-Alternating-Gas injection method or WAG injection, that combines the effects of the two fluids to the reservoir. There are three main parameters that affect the performance of this method, such as gas injection rate, WAG ratio, and number of cycles. A sensitivity study will be operated by using CMG GEMTM to determine the optimum value for each of the parameters which generates the highest oil recovery. The result of this study shows that the injection method of WAG results in 4.76% higher oil recovery from the primary production. This result is higher compared to the continuous water and continuous gas injection ones. The findings of this study also show that the injection method by using the hydrocarbon gas as the injection fluid results in higher oil recovery compared to the CO2 gas one. By using these results, the optimization for each parameter was then simulated and found that the most optimum scenario to be implemented at “B” structure of “S” field is by using WAG injection method with water injection of 2500 BPD and hydrocarbon gas injection of 0.25 MMSCFD by applying 1:2 WAG ratio and 8 number of cycles scheme.