基于修正气液相平衡模型的微⁃纳米孔中油气相行为预测

doi:10.12422/j.issn.1006-396X.2025.04.006

摘要/Abstract

摘要：

多数油气生产问题源于不正确的油气相行为模拟，微?纳米孔中油气相行为对页岩油气开发至关重要。因此，准确模拟微?纳米孔中的油气相行为，是页岩油气高效开发的关键。考虑毛细管压力和流体临界点偏移对微?纳米孔中热力学相平衡的影响，耦合体积平移的Peng?Robinson状态方程（PR?EOS），构建了一个微?纳米孔限域下的气液平衡（VLE）模型，其预测相对误差小于1.53%；基于改进的VLE模型，研究了限域下微?纳米孔效应对Bakken页岩油相行为的影响规律。结果表明，微?纳米孔限域效应降低了气?液相密度差和轻质组分平衡常数K，并且缩小了相包络面积；随着孔隙半径减小，气液界面张力（IFT）先缓慢降低，然后快速降低，其中孔隙半径20 nm为下降速率转折点。该研究可为非常规油气资源的开发提供重要的理论基础支持。

关键词: 微?纳米孔, 气液相平衡, 限域效应, 相行为, 地质封存

Abstract:

Improper models of phase behavior are a major cause of many production problems faced by shale gas reservoirs. The phase behavior of oil?gas in micro?nano pores is crucial for shale oil and gas development. Considering the effects of capillary pressure and critical point shift on the thermodynamic phase equilibrium in micro?nano pores, a vapor?liquid equilibrium (VLE) model in the confined micro?nano pores was developed by using a volume?translated Peng?Robinson Equation of State(PR?EOS), and the relative error of prediction was less than 1.53%. Based on the improved VLE model, the phase behavior of hydrocarbon mixtures such as Bakken shale oil in the confined space was investigated. Results indicate that the nanopore confinement decreases the vapor?liquid density difference and equilibrium coefficient(K) of the light components and shrinks the phase envelope. As the pore size decreases, the interfacial tension (IFT) first decreases slowly and then drops sharply, particularly when the pore radius is less than 20 nm.This study can provide an important theoretical foundation to support the development of unconventional oil?gas resources.

Key words: Micro?nano pores, Vapor?liquid equilibrium, Confined effect, Phase behavior, Geological storage

中图分类号:

TE319

陈影影, 杨付林, 陈雄. 基于修正气液相平衡模型的微⁃纳米孔中油气相行为预测[J]. 石油化工高等学校学报, 2025, 38(4): 43-50.

Yingying CHEN, Fulin YANG, Xiong CHEN. Phase Behavior Modeling of Hydrocarbon Mixtures in Micro⁃Nano Pores Using a Modified Vapor⁃Liquid Equilibrium Model[J]. Journal of Petrochemical Universities, 2025, 38(4): 43-50.

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链接本文: https://journal.lnpu.edu.cn/syhg/CN/10.12422/j.issn.1006-396X.2025.04.006

https://journal.lnpu.edu.cn/syhg/CN/Y2025/V38/I4/43

图/表 10

图1 VLE计算模型的工作流程图

Fig.1 A workflow of the prososed VLE algorithem

图2 改进的VLE模型对气液密度模拟结果与实验结果对比

Fig.2 Comparison of gas?liquid density simulation results and experimental results using an improved VLE model

表1 三元体系中各组分K的实验值与模拟值对比

Table 1 Comparison between experimental and simulated data of K components in ternary system

组分	Z_i /mol	K		相对误差/%
组分	Z_i /mol	实验值	模拟值	相对误差/%
i⁃C₄H₁₀	0.618 9	2.652 0	2.637 0	0.57
n⁃C₄H₁₀	0.181 1	1.885 0	1.888 0	0.16
n⁃C₈H₁₈	0.200 0	0.052 4	0.051 6	1.53

表2 四元组分模拟油的组成及各组分的物性参数[33]

Table 2 The compositions and physical properties of the constituting components for four?component model oil[33]

组分	Z_i /mol	T_c/K	p_c/MPa	ω_i	M_i /（g·mol^-1）	p_ch_i /（cm³·mol·g^-3/4）
CO₂	0.800 0	304.21	7.384	0.225 0	44.01	82.00
CH₄	0.050 0	190.58	4.604	0.010 4	16.04	74.05
n⁃C₄H₁₀	0.060 0	425.18	3.797	0.201 0	58.12	193.90
n⁃C₁₀H₂₂	0.090 0	617.65	2.115	0.490 0	142.29	440.69

表3 Bakken页岩油的组成及各组分的物性参数[34]

Table 3 The compositions and physical properties of the constituting components for Bakken shale oil

组分	Z_i /mol	T_c/K	p_c/MPa	ω_i	M_i /（g·mol^-1）	p_ch_i /（cm³·mol·g^-3/4）
C₁	0.250 6	190.60	4.604	0.008 0	16.04	77.00
C₂-C₄	0.220 0	363.30	4.310	0.143 2	42.82	145.20
C₅-C₇	0.200 0	511.56	3.421	0.247 4	83.74	250.00
C₈-C₉	0.130 0	579.34	3.132	0.286 1	105.91	306.00
C₁₀₊	0.199 4	788.74	2.187	0.686 9	200.00	686.30

图3 不同孔隙半径下四元组分模拟油和Bakken页岩油的各组分气液平衡常数

Fig.3 Vapor?liquid equilibrium coefficient of each component for the quaternary component model oil and Bakken shale oil under different pore sizes

图4 不同孔隙半径下四元组分模拟油和Bakken页岩油的气液相密度

Fig.4 Gas liquid phase density of the quaternary component model oil and Bakken shale oil under different pore radii

图5 不同压力下四元组分模拟油和Bakken页岩油的气液界面张力随孔隙半径的变化规律

Fig.5 Variation of gas?liquid interfacial tension with pore radius in simulated oil and Bakken shale oil under different pressures using quaternary components

图6 不同压力下四元组分模拟油的pcap随孔隙半径的变化规律

Fig.6 pcap change of the quaternary component model oil with pore sizes under different pressures

图7 不同孔隙半径下Bakken页岩油的p?T相包络线

Fig.7 p?T phase envelopes of the Bakken oil under different pore sizes

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