Perpustakaan Digital ITB

Due to its greater advantages over conventional EOR methods in terms of costs, environmental impact, and field process implementation, low salinity water injection (LSWI) is currently gaining traction in the oil industry and is considered as a critical EOR method. According to recent studies, combining LSWI with CO2 injection as low salinity water alternating CO2 (LSWA-CO2) injection can further boost oil recovery by promoting the synergy of underlying these two methods and can overcome the late-production issue that commonly emerges due to conventional WAG injection. CEC distribution in LSWA-CO2 significantly influences the multiple ionic exchange mechanism for incremental oil recovery. However, the previous studies of LSWA-CO2 were only limited to a homogenous CEC distribution model for simplification. Accordingly, to obtain more reliable results, this study will design LSWA-CO2 injection in the “B” Structure “S” Field using the heterogenous CEC distribution. By using the Adjusted Neuman correlation, the average CEC value in this field is about 656.23 eq/m3, which is higher than homogenous CEC distribution approaches that lead to higher oil recovery. As a sandstone reservoir, the "S" field contains clay minerals, including illite and kaolinite, and has a mixed-wet wettability suitable for LSWA-CO2 implementation. In order to obtain the best possible design for the proposed mechanism, four injection parameters will be evaluated: injected water salinity, water injection rate, gas injection rate, and cycle ratio. The impact of these designing parameters was investigated through reservoir simulation and sensitivity study utilizing CMG software. The results of the study indicate that the optimum injection parameters for LSWA-CO2 injection in the "B" Structure "S" Field are an injected water salinity of 1334.061 ppm (dilution 15 times of formation water), a water injection rate of 1700 BWPD, a gas injection rate of 0.05 MMSCFD, and a cycle ratio of 2:1 with oil recovery factor up to 64.14%. In all cases, introducing LSWA-CO2 to the reservoir shows a great advantage in terms of enhancing wettability alteration, mineral dissolution, and controlling the displacement front of the injected fluid through mobility control.