Hybrid EOR Performance Optimization through Flue Gas−Water Alternating Gas (WAG) Injection: Investigating the Synergistic Effects of Water Salinity and Flue Gas Incorporation Mehdi Nassabeh, Zhenjiang You,* Alireza Keshavarz, and Stefan Iglauer Cite This: https://doi.org/10.1021/acs.energyfuels.4c00757 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information ABSTRACT: 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 CO 2 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, CO 2 , and low salinity water, as well as the optimization of injection patterns for flue gas-LSWAG and CO 2 - 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 CO 2 , 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 CO 2 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 CO 2 -HSWAG outperforming CO 2 -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 CO 2 -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. 1. INTRODUCTION Enhanced oil recovery (EOR) techniques have gained significant importance in the modern oil industry. These methods, tailored to specific conditions, offer distinct advan- tages and limitations. To optimize results, EOR must be implemented under specific circumstances. 1−5 In an effort to enhance oil reservoir production, novel EOR methods and combinations have been proposed. 6−9 Gas injection, a widely used recovery method, effectively boosts oil production by elevating reservoir pressure and displacing oil toward production wells. However, challenges like reservoir hetero- geneity, mobility control, gas miscibility, operational hurdles, and wellbore damage need to be effectively managed for successful gas injection projects. 10−13 To address these challenges and enhance the sweeping efficiency of oil reservoirs, a solution known as the water alternating gas (WAG) injection method has been pro- posed. 14,15 This technique involves injecting water and gas into the reservoir at specific intervals. The process includes injecting a volume of gas after a volume of water is injected for predetermined periods. The alternating injection of water and gas facilitates the simultaneous sweeping of crude oil in both the upper and lower regions of the reservoir. 16−18 This method effectively improves the sweeping of oil on a macroscopic scale by employing the cyclic nature of WAG. As gas and water slugs penetrate through porous media, they reduce the viscosity of oil by dissolving gas into the oil phase. 19,20 The primary challenge in oil production from carbonate reservoirs is the substantial amount of residual oil that is either adsorbed to the rock surface or trapped within the pores. This phenomenon is influenced by two significant factors: (1) the Received: February 19, 2024 Revised: June 22, 2024 Accepted: June 24, 2024 Article pubs.acs.org/EF © XXXX American Chemical Society A https://doi.org/10.1021/acs.energyfuels.4c00757 Energy Fuels XXXX, XXX, XXX−XXX Downloaded via EDITH COWAN UNIV on July 17, 2024 at 03:52:27 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.