Evaluating Deep Eutectic Solvent as a Novel Enhanced Oil Recovery Method

Oil and gas are still primary energy source in the world, despite the advancements in renewable energy. Enhanced Oil Recovery (EOR) has an important task for increasing oil recovery, especially for heavy oil reservoirs. Many researchers showed chemical enhanced oil recovery, particularly surfactant is most efficient method in many reservoirs. But most of these projects were not commercially successful due to high cost and environmental issues. Ionic liquids (ILs) gained more attention as an alternative to surfactants. But synthesis and purification processes makes them expensive for industrial application and some types of them are toxic and not biodegradable. Recently, another form of ILs, namely Deep Eutectic Solvents (DESs) were discovered as cheaper and greener alternative to conventional ILs. DESs are cost-effective, easy to prepare, non-toxic, recyclable, biodegradable and environmental-friendly. DES is composed of at least two cheap and safe component that are able to form eutectic mixture with melting point lower than its individual components. Due to mentioned advantages, DESs have found application in different fields including oil and gas industry. Main applications of DESs in oil and gas industry are separation processes such as dearomatization, desulfurization, purification of biodiesel and CO2 capture. In this paper, performance of DESs in EOR process were evaluated as a novel EOR method. Their effects on different EOR mechanisms such as stable emulsion formation, IFT reduction between oil and DES/brine solution, wettability alteration, oil recovery improvement and formation damage were analyzed and compared each other. Economic aspect was also looked through by showing a cost of other chemical EOR methods. Injection of DES solutions showed significant amount of oil recovery. Total oil recovery was even higher when steam flooding performed after DES injection. Wettability alteration and viscous forces were main mechanisms for oil recovery improvement. Only malonic acid (MA) based DESs showed limited emulsion formation with oil, others didn’t have emulsification capacity. For heavy oil reservoirs, increase of IFT rather than decrease was observed. For light and medium oil reservoirs, IFT reduction was seen. Moreover, DESs didn’t show any formation damage. Comparing the performance of DESs by considering additional oil recovery due to DES injection after brine flooding, Choline Chloride (ChCl):Glycerol (1:2) showed best performance with an additional oil recovery of up to 30 %OOIP. Cost assessment showed this method will have lower cost compared to other chemical methods but detailed techno-economic analysis should be performed.