Visual characterization, exergy and mechanism analysis of in-situ nonequilibrium dynamic phase-behavior of CO2-oil

Yiqi Zhang, Shenglai Yang, Yun Luo, Yuning Han, Lerao Tian, Qing Liu, Xinyuan Gao, Bin Shen, Renfeng Yang and Jing Li

Energy, 2025, vol. 328, issue C

Abstract: CO2-enhanced oil recovery (EOR) is the key technology for upstream petroleum industry to transition towards sustainable development. The phase-behavior of CO2-oil is the scientific basis for studying CO2-EOR. In this paper, the in-situ miscibility of CO2-different oils is described continuously by using visual Pressure-Volume-Temperature (PVT) cell, and the dominant mass transfer effect at different pressures is analyzed. Then, based on the results of PVT physical properties and oil-component changes, phase-behavior differences and miscibility mechanism are investigated. Finally, the advanced exergy analysis of miscible process is carried out, and the effect of different phase-behavior on oil development is evaluated. The results show that the miscible process of CO2-oil can be divided into three stages. The main mass transfer in the primary oil expansion stage is CO2 dissolution. In the transition stage of mass transfer, CO2 and oil begin to transfer mass to each other, CO2 dissolution and oil extraction coexist, and the dominant mass transfer effect changes. The main mass transfer in miscible stage is the transfer of oil to CO2 and the realization of miscibility. The pressure is the driving factor of miscibility, and the composition of oil is the essential reason to determine the result of miscibility, the remaining components of different oils show a normalization trend dominated by heavy components in miscible process. The result of exergy calculation can effectively reflect the direction and intensity of mass transfer, and selecting the pressure range corresponding to the positive peak of exergy can improve the effect of phase-behavior on oil development.

Keywords: In-situ phase-behavior; Visual extraction experiment; Mass transfer; Miscible mechanism; Advanced exergy analysis; Injection pressure selection (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:328:y:2025:i:c:s0360544225022029

DOI: 10.1016/j.energy.2025.136560

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