The effect of CO2-philic thickeners on gravity drainage mechanism in gas invaded zone. (1st January 2023)

• Record Type: Journal Article
• Authors: Gandomkar, Asghar; Reza Nasriani, Hamid; Enick, Robert M.; Torabi, Farshid
• Is Part Of: Fuel. Volume 331:Part 1(2023)
• Publication Date: 2023-01-01
• Subjects: Gas invaded zone -- Gas thickeners -- CO2 diffusion coefficients -- Gravity drainage -- Matrix-fracture system -- Cloud point pressure; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.125760
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Improving the oil recovery in gas invaded zone by PFA as a CO2 -philic thickener. The PFA thickener improved gravity drainage mechanism due to a decrease in the IFTs. The mass transfer was decreased due to heterogeneity compared to the bulk oil phase. The CO2 diffusion coefficients were increased during PFA/CO2 injection. 16 % additional oil recovery was achieved during PFA/CO2 in the gas invaded zone. Abstract: The rate of mass transfer between the fractures and matrix in gas invaded zone can significantly influence on the oil recovery during the forced gravity drainage process. However, in this study, a new approach was suggested to improve the gravity drainage process in gas invaded zone. Poly(fluoroacrylate) (PFA), as a CO2 -philic thickener, was injected into the gas invaded zone to illustrate the impact of interfacial mechanisms such as gas diffusion coefficient and interfacial tension (IFT) on oil recovery. Also, the cloud point pressures were measured to ensure that the PFA did not come out of the solution due to a phase change during IFT, gas diffusion coefficient, and gravity drainage experiments. Results showed that the CO2 -PFA thickener (20000 ppm) could decrease the IFT from 56 to 24 dyne/cm compared to the pure CO2 scenario, improving the gravity drainage mechanism in the gas invaded zone. In addition, the CO2 diffusion coefficients were increased approximately more than two times during CO2 -PFA injection in comparison with pure CO2 injection in both porous media and bulk oil phase scenarios at reservoir conditions. Also, an incremental oil recovery of 16 percent was achieved during PFA/CO2 compared to pure CO2 injection in the gas invaded zone. Therefore, gas gravity drainage is the most important mechanism once gas thickener or CO2 enters the fractures in the gas invaded zone.