A critical review of CO2 enhanced oil recovery in tight oil reservoirs of North America and China

• Published in: Fuel (Guildford) 2020-09, Vol.276, p.118006, Article 118006
• Main Authors: Song, Zhaojie, Song, Yilei, Li, Yuzhen, Bai, Baojun, Song, Kaoping, Hou, Jirui
• Format: Article
• Language: English
• Subjects: Carbon dioxide; CO2 injection; Computer simulation; Coupling (molecular); Diffusion effects; Economic conditions; Enhanced oil recovery; Exploitation; Field tests; Geomechanics; High pressure; Horizontal wells; Hydraulic fracturing; Literature reviews; Mathematical models; Minerals; Molecular diffusion; Oil; Oil exploration; Oil recovery; Oil reservoirs; Oil shale; Porosity; Recovery mechanism; Reservoirs; Rocks; Simulation; Tight oil reservoir
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.118006

•A comprehensive literature review was conducted on CO2-EOR in tight oil reservoirs.•Specialized technologies are needed in the exploitation of China’s tight reservoirs.•The effect of CO2 diffusion is relatively exaggerated in experimental results.•CO2-crude oil interaction in nanopores may lead to an oil recovery increment.•CO2-water-minerals interaction influences the geomechanical properties of rock. Primary oil recovery remains less than 10% in tight oil reservoirs, even after expensive multistage horizontal well hydraulic fracturing stimulation. Substantial experiments and simulation works have been performed to investigate CO2 enhanced oil recovery (CO2-EOR) potential in tight reservoirs; however, some results conflict with each other. The objectives of this paper are to fully understand the CO2-EOR mechanisms and to figure out the difference between tight oil exploitation in North America and China through a comprehensive literature review. It is shown that compared with Bakken and Eagle Ford formation, China’s tight oil reservoirs feature higher mud content and oil viscosity while they have a lower brittleness index of rock and formation pressure coefficient, leading to confined stimulated reservoir volume and further limited CO2-oil contact. The effect of CO2 molecular diffusion is relatively exaggerated in experimental results, which can be attributed to the dual restrictions of exposure time and oil-CO2 area in field scale. Numerical simulation works show that the shifted phase properties in nanopores lead to an oil recovery increment. The development of nano-scale chips withholding high pressure/temperature may advance the experimental study on the nanopore confinement effect. CO2-fluid-rock minerals interaction might be more complex due to the large specific surface area of nanopores in tight formations. The geomechanics coupling effect cannot be ignored when examining the CO2-EOR performance in tight reservoirs. And a comprehensive simulation study coupling with technical and economic feasibility is highly recommended before running a field test of CO2-EOR.