Investigation of Polymer-Assisted CO2 Flooding to Enhance Oil Recovery in Low-Permeability Reservoirs

Abstract

CO2 flooding is a favorable technical means for the efficient development of low-permeability reservoirs, and it can also contribute to the realization of net-zero CO2 emissions. However, due to the unfavorable viscosity ratio and gravity overriding effect, CO2 channeling will inevitably occur, seriously affecting its storage and displacement effects. This paper conducts a systematic study on the application of polymer-assisted CO2 flooding in low-permeability reservoirs. Firstly, the polymer agent suitable for low-permeability reservoirs is optimized through the viscosity-increasing, rheological, and temperature- and salt-resistant properties of the solution. Then, the injectivity performance, resistance-increasing ability, and profile-improving effect of the polymer solution were evaluated through core experiments, and the optimum concentration was optimized. Finally, the enhanced oil recovery (EOR) effects of polymer-assisted and water-assisted CO2 flooding were compared. The results show that the temperature-resistant polymer surfactant (TRPS) has a certain viscosity-increasing performance, good temperature resistance performance, and can react with CO2 to increase the solution viscosity significantly. Meanwhile, TRPS has good injection performance and resistance-increasing effect. The resistance increasing factor (η and η′) of TRPS-assisted CO2 flooding increases with increased permeability, the concentration of TRPS solution, and injection rounds. Considering η′ and the profile improvement effect comprehensively, the application concentration of TRPS should be 1000 mg/L. The EOR effect of TRPS-assisted CO2 flooding is 8.21% higher than that of water-assisted CO2 flooding. The main effective period is in the first and second rounds, and the best injection round is three. The research content of this paper can provide data support for the field application of polymer-assisted CO2 flooding in low-permeability reservoirs.

Enhanced Oil Recovery Using Polymer Alternating CO2 Gas Injection: Mechanisms, Efficiency, and Environmental Benefits

“…An early attempt to mimic the realistic PAG flooding scenario involved sand-pack flooding, highlighting the effectiveness of immiscible PAG injection in extracting heavy oil where PAG injection in the tertiary mode yielded 19% oil recovery . Few coreflood experiments on sandstone cores have been conducted to demonstrate the efficacy of PAG injection, but these experiments either used model crude oil or lacked comprehensive discussion on the displacement mode of crude oil by CO 2 during PAG injection. , A micromodel study was conducted to explain the recovery mechanism of miscible PAG for 0.5 cP oil using SAV55 polymer . Furthermore, Tovar et al studied the effect of heterogeneity on miscible or immiscible displacement of oil by PAG injection in sandstone core, and their findings indicated that a certain level of heterogeneity is necessary for PAG injection to yield beneficial results.…”

Pore-Scale Transport Dynamic Behavior of Microspheres and Their Mechanisms for Enhanced Oil Recovery

“…Channeling of the injected fluid due to reservoir heterogeneity will reduce the swept fluid volume and reduce oil recovery. , No matter whether conventional or unconventional reservoirs − or gas − or water injection, plugging the dominant channels and expanding the swept volume of the injected fluid are the developmental ideas throughout the whole process of oil and gas field development . Additionally, due to the influence of reservoir wettability, the injected fluid tends to invade the pore throats with the least flow resistance under the action of a capillary force, which will also lead to the formation of dominant channels. , Therefore, the optimal selection of profile control agents and the revelation of their transport and plugging mechanisms in porous media are the focus of research. − …”

Research on Performance Evaluation of Polymeric Surfactant Cleaning Gel-Breaking Fluid (GBF) and Its Enhanced Oil Recovery (EOR) Effect

“…Meanwhile, Dai et al also pointed out that osmotic pressure is an additional phenomenon that reduces interfacial tension and is the main controlling factor for gel-breaking fluids to improve oil recovery through studies on the adsorption rules of surfactants at the oil-water rock interface [31,32]. In addition, CO 2responsive clean fracturing fluid also has good application prospects [33][34][35].…”