ABSTRACT Phase behavior of confined fluid demonstrates significant deviation from that of bulk fluid because of the strong molecule-wall interaction and geometric constraint in confined space, resulting in the inapplicability of the classical cubic equation of state (EOS). The objective of this work is to modify the Peng-Robinson EOS (PR EOS) with respect to both the attractive parameter and the covolume term to reflect the impact of molecule-wall interaction and geometric constraint, respectively. The modified PR EOS is applied to compute the phase diagrams of CO2+n-C4H10 and CO2+n-C10H22 binary mixtures, CO2+n-C4H10+n-C10H22 ternary mixture, and CO2+Eagle Ford condensate in nanopores. In this work, correlations of both critical temperature and critical pressure shift with nanopore sizes are proposed to compute the confined attractive parameter and the confined covolume in the modified PR EOS. The proposed EOS model is validated by both the critical temperature and the critical pressure shift data collected from literature. Results demonstrate that confinement effect in nanopores impose an overall shrinkage to the two-phase diagrams of all the CO2-hydrocarbon systems. The upper dew-point pressure of the Eagle Ford condensate sample is calculated to be 2972.6 psi, with a suppression of 27.56% compared to the bulk value of 4103.6 psi. Moreover, the size of the two-phase region in the ternary diagram and the minimum miscibility pressure also decreases in confined space, which is in favor of the miscible gas injection enhanced oil recovery by increasing the possibility of achieving first contact miscibility.

中文翻译：

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纳米孔内 CO2/碳氢化合物系统的修正 Peng-Robinson 状态方程

摘要 由于密闭空间中的强分子-壁相互作用和几何约束，密闭流体的相行为与本体流体的相行为存在显着差异，导致经典三次状态方程 (EOS) 不适用。这项工作的目的是修改 Peng-Robinson EOS (PR EOS) 的吸引力参数和共体积项，以分别反映分子-壁相互作用和几何约束的影响。应用改进的 PR EOS 计算纳米孔中 CO2+n-C4H10 和 CO2+n-C10H22 二元混合物、CO2+n-C4H10+n-C10H22 三元混合物和 CO2+Eagle Ford 冷凝物的相图。在这项工作中，提出了临界温度和临界压力偏移与纳米孔尺寸的相关性，以计算改进的 PR EOS 中的受限吸引参数和受限共体积。提出的 EOS 模型通过从文献中收集的临界温度和临界压力偏移数据得到验证。结果表明，纳米孔中的限制效应对所有 CO2-烃系统的两相图施加了整体收缩。Eagle Ford 冷凝水样品的上露点压力计算为 2972​​.6 psi，与 4103.6 psi 的整体值相比，抑制了 27.56%。此外，三元图中两相区的大小和最小混相压力也在密闭空间中减小，