Perpustakaan Digital ITB

Low Salinity Water Injection (LSWI) has become an attractive enhanced oil recovery (EOR) method for improving the oil recovery compared to other conventional waterflood. It has been acknowledged that combining LSWI with other EOR techniques resulted in significant advantages. While LSWI is an emerging EOR method based on wettability alteration from oil-wet to water-wet conditions, WAG is a proven technique for improving gas flooding performance by controlling gas mobility. To further enhance oil recovery and solve the late production problem that is present in conventional WAG, Low Salinity Water Alternating Gas (LSWAG) injection promotes the synergy of the mechanisms underlying these methods (i.e., ion exchange, wettability alteration, CO2 miscible displacement, and mobility control). As the efforts to reduce greenhouse gas emissions are receiving widespread attention lately, the oil and gas industry will have to play a big part. One option is to implement initiatives that offset emissions by utilizing CO2 on large scale for underground storage. However, the LSW interaction with CO2 (LSWA-CO2) for CO2 dissolution and oil recovery applications has been discussed in limited literature as far as we are aware. In this paper, the author presents the results of a sensitivity study of different LSWA-CO2 gas injection scenarios to investigate the effects of injection operational parameters and to propose the most optimum injection scenario to be applied in the sandstone reservoir at “B” Structure in “S” Field, South Sumatera Province, Indonesia. Reservoir simulations, production forecasts, and evaluation of trapping mechanisms were done using CMG GEM Simulator for 15 years of LSWA-CO2 gas injection period and was followed by 25 years post-injection period. Water salinity, number of cycles, and gas-water ratio were varied to observe the effects of those parameters on the oil recovery factor and CO2 storage efficiency. The findings of this study showed that the influence of injection water salinity is insignificant on oil recovery and CO2 storage efficiency due to the high injection gas rate. Furthermore, increase in number of LSWAG cycles causes an increase in oil recovery and improves CO2 storage efficiency. Also, it has been found that LSWAG ratios affect the oil recovery and CO2 storage efficiency where less ratios are preferable. Thus, the author determine that the proposed optimum scenario of LSWA-CO2 gas injection to be applied in the sandstone reservoir at “B” Structure in “S” Field is injection water salinity of 3600 ppm, 2 LSWAG cycle/year, and LSWAG ratio of 0.5.