Hybrid EOR Performance Optimization through Flue Gas–Water Alternating Gas (WAG) Injection: Investigating the Synergistic Effects of Water Salinity and Flue Gas Incorporation

To enhance oil production from carbonate reservoirs, the implementation of advanced enhanced oil recovery (EOR) techniques has been proposed. This research evaluates the potential of flue gas and CO2 in water alternating gas (WAG) injection in a homogeneous fractured carbonate reservoir characterized by low porosity and permeability, incorporating water salinity as a hybrid method. Simulations were conducted using Eclipse (E300) software to assess the effectiveness of this approach. The optimization of the hybrid EOR method, including modified hybrid EOR, simultaneous water and gas (SWAG) incorporating flue gas, CO2, and low salinity water, as well as the optimization of injection patterns for flue gas-LSWAG and CO2-LSWAG, were analyzed to achieve the optimal oil recovery factor. The simulation results indicated that natural production from the reservoir accounted for only 29% of the total, highlighting the necessity of implementing EOR methods to enhance oil recovery. Three types of flue gases, derived from steel, cement, and power plants, along with CO2, were considered in this study. The findings revealed that modification of the hybrid EOR method resulted in the highest oil recovery factor, reaching approximately 85%. Additionally, gas injection using CO2 exhibited a higher oil recovery factor compared to flue gas injection, which demonstrated the lowest performance. Therefore, the hybrid flue gas-WAG method was recommended due to its significant increase in the recovery factor. Furthermore, the study investigated the impact of water salinity on performance, with CO2-HSWAG outperforming CO2-LSWAG in terms of recovery factor, indicating a positive response to an increase in water salinity. Conversely, the evaluation of flue gases had a negative effect on oil recovery. The study also observed the positive effectiveness of exceeding gas injection patterns in CO2-LSWAG, as well as the sensitivity of flue gas compositions on the oil recovery factor. Thus, this research illustrated the diverse potential of flue gases in hybrid EOR.