Abstract：
CO2 flooding is a dynamic process. In order to analyze the interaction and phase behavior of the CO2-oil system and component variation of liquid and gas during CO2 flooding, swelling/extraction tests and interfacial tension tests were conducted. The solubility of CO2 in crude oil, the oil swelling factor and the interfacial tension between CO2 and oil was investigated. The dynamic mass-transfer efficiency of the CO2-oil system in porous media was further clarified through coreflood tests. Results revealed that when the operation pressure is less than minimum extraction pressure, the CO2 could only extract a small amount of light components and dissolve in the crude oil to expand the oil so that gas channeling and viscous fingering is easy to occur because of an obvious gas-liquid interface. On the other hand, CO2 miscible flooding could cause a large amount of medium and heavy components to remain in the reservoir, which will create great difficulties for the subsequent EOR measures. CO2 near-miscible flooding can displace more than two-thirds of the asphaltene in the crude oil, which could prevent asphaltene from plugging pores and throats of the reservoir. Therefore, CO2 near-miscible flooding is a reliable EOR technique.
Key words：CO2-oil system; swelling/extraction test; minimum extraction pressure; interfacial tension; minimum miscibility pressure; displacement mechanism
Corresponding Authors：yangsl@cup.edu.cn
Cite this article：QIAN Kun, YANG Shenglai, DOU Hongen, WANG Qian, HUANG Yu, WAN Teng, ZHANG Yuxiang. Interaction of the CO2-oil system and displacement mechanisms during CO2 flooding. Petroleum Science Bulletin, 2019, 01: 69-82
