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ABSTRAK Gerry Adam Alwyn Syah
PUBLIC Suharsiyah

2020 TA PP GERRY ADAM ALWYN SYAH 1.pdf)u
Terbatas Suharsiyah
» ITB

Several studies have shown that low salinity water injection is an emerging EOR technique to offer significant advantages than conventional or high salinity waterflood method due to its potential in adding the oil recovery by 5-20% as a secondary recovery in sandstone reservoir. Later the study was continued and led to the idea of combining low salinity water injection with other EOR technique. One of the most applicable combination is by injecting low salinity water and miscible or immiscible gas injection alternately or known as LSWAG. It is believed as a proven method in controlling the gas mobility for improving sweep efficiency, supported by wettability alteration into more water-wet as a consequence of geochemical interaction between rock and reservoir fluids. Until recently, CO2 gas is the most preferred to be used in alternating low salinity water as its availability and affordability in most field cases. Thus, the CO2-LSWAG promotes the idea of synergized mechanism between these two methods that further increase macroscopic and microscopic efficiency, leading to higher oil recovery. This study aims to design the compositional model of low salinity water alternating CO2 gas (CO2-LSWAG) injection for its application into sandstone reservoir in “T” Structure at “S” Field, Indonesia. Reservoir simulation and production forecast were performed by using CMG GEMTM during 6 years production period with preliminary work in CMG WINPROPTM for generating reservoir fluid compositional model. Series of sensitivity was conducted to find the best production scheme and operational parameters of CO2-LSWAG injection. The reasonable explanations behind its behavior in contributing higher oil recovery are proposed by comparing its performance with low salinity water injection, and later found through the simulation that sweep efficiency improvement supported by mineral dissolution enhancement plays an important role in reducing oil saturation. The results of this study conclude that secondary recovery technique of CO2-LSWAG injection is more preferable to be implemented by continuous injection for 6 years with longer and equal ratio between gas and water injection time length for a single year period. The best operational parameters are proposed by injecting immiscible CO2 gas injection rate 5 MMSCFD alternate with low salinity water with injection rate 1200 BPD and concentration 1711 ppm in a year period which gives the additional recovery factor about 5.09% from base case scenario. Therefore, CO2-LSWAG injection is suggested to be applied in “S” field for further development.