Phase Behavior Modeling of Hydrocarbon Mixtures in Micro⁃Nano Pores Using a Modified Vapor⁃Liquid Equilibrium Model

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

Abstract

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

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

CLC Number:

TE319

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.

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.

0
/ / Recommend

Add to citation manager EndNote|Ris|BibTeX

URL: https://journal.lnpu.edu.cn/syhg/EN/10.12422/j.issn.1006-396X.2025.04.006

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

Figures/Tables 10

Fig.1 A workflow of the prososed VLE algorithem

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

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

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

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

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

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

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

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

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

References 35

[1]	瞿恒，邬忠虎. 三轴应力下含交叉裂缝页岩的力学特性及破坏模式数值模拟［J］. 辽宁石油化工大学学报， 2024， 44（2）： 42⁃49.
	QU H， WU Z H. Numerical simulation of mechanical properties and damage modes of shales with cross⁃fractures under triaxial stress［J］. Journal of Liaoning Petrochemical University， 2024， 44（2）： 42⁃49.
[2]	何晋译，冷筠滢，李志明，等. 不同岩相泥页岩生烃能力与含油性特征--以玛湖凹陷风城组玛页1井为例［J］. 东北石油大学学报， 2025， 49（1）： 1⁃17.
	HE J Y， LENG Y Y， LI Z M， et al. Hydrocarbon generation capacity and oil⁃bearing properties of shale with different lithofacies： A case study of well Maye 1 in Fengcheng Formation， Mahu Sag［J］. Journal of Northeast Petroleum University， 2025， 49（1）： 1⁃17.
[3]	陈洋，尹楠鑫，陈岑，等. 陆相页岩油有机质来源与沉积环境分析--以苏北盆地高邮凹陷花庄地区古近系阜宁组二段为例［J］. 东北石油大学学报， 2024， 48（6）： 17⁃30.
	CHEN Y， YIN N X， CHEN C， et al. Organic matter sources and depositional environment analysis of continental shale oil： A case study of Paleogene second member in Funing Formation in the Huazhuang Area， Gaoyou Sag， Subei Basin［J］. Journal of Northeast Petroleum University， 2024， 48（6）： 17⁃30.
[4]	SONG Y L， SONG Z J， GUO J， et al. Phase behavior and miscibility of CO₂–hydrocarbon mixtures in shale nanopores［J］. Industrial & Engineering Chemistry Research， 2021， 60（14）： 5300⁃5309.
[5]	MOHAGHEGHIAN E， HASSANZADEH H， CHEN Z X. Evaluation of shale⁃gas⁃phase behavior under nanoconfinement in multimechanistic flow［J］. Industrial & Engineering Chemistry Research， 2020， 59（33）： 15048⁃15057.
[6]	LI L， SHENG J J. Nanopore confinement effects on phase behavior and capillary pressure in a Wolfcamp shale reservoir［J］. Journal of the Taiwan Institute of Chemical Engineers， 2017， 78： 317⁃328.
[7]	LUO S， JIN B K， LUTKENHAUS J L， et al. A novel pore size⁃dependent equation of state for modeling fluid phase behavior in nanopores［J］. Fluid Phase Equilibria， 2019， 498： 72⁃85.
[8]	SANDOVAL D R， YAN W， MICHELSEN M L， et al. Influence of adsorption and capillary pressure on phase equilibria inside shale reservoirs［J］. Energy & Fuels， 2018， 32（3）： 2819⁃2833.
[9]	WANG Z D， LIU T Y， LIU S C， et al. Adsorption effects on CO₂⁃oil minimum miscibility pressure in tight reservoirs［J］. Energy， 2024， 288： 129815.
[10]	LIU X Y， ZHANG D X. A review of phase behavior simulation of hydrocarbons in confined space： Implications for shale oil and shale gas［J］. Journal of Natural Gas Science and Engineering， 2019， 68： 102901.
[11]	TAN S P， QIU X D， DEJAM M， et al. Critical point of fluid confined in nanopores： Experimental detection and measurement［J］. Journal of Physical Chemistry C， 2019， 123（15）： 9824⁃9830.
[12]	WU K L， CHEN Z X， LI X F， et al. Methane storage in nanoporous material at supercritical temperature over a wide range of pressures［J］. Scientific Reports， 2016， 6： 33461.
[13]	JIN Z H， FIROOZABADI A. Phase behavior and flow in shale nanopores from molecular simulations［J］. Fluid Phase Equilibria， 2016， 430： 156⁃168.
[14]	ZHAO Y N， JIN Z H. Hydrocarbon⁃phase behaviors in shale nanopore/fracture model： Multiscale， multicomponent， and multiphase［J］. SPE Journal， 2019， 24（6）： 2526⁃2540.
[15]	BRUSILOVSKY A I. Mathematical simulation of phase behavior of natural multicomponent systems at high pressures with an equation of state［J］. SPE Reservoir Engineering， 1992， 7（1）： 117⁃122.
[16]	ABU AL⁃RUB F A， DATTA R. Theoretical study of vapor–liquid equilibrium inside capillary porous plates［J］. Fluid Phase Equilibria， 1999， 162（1⁃2）： 83⁃96.
[17]	HAMADA Y， KOGA K， TANAKA H. Phase equilibria and interfacial tension of fluids confined in narrow pores［J］. The Journal of Chemical Physics， 2007， 127（8）： 084908.
[18]	TAN S P， PIRI M. Retrograde behavior revisited： Implications for confined fluid phase equilibria in nanopores［J］. Physical Chemistry Chemical Physics， 2017， 19（29）： 18890⁃18901.
[19]	NOJIABAEI B， JOHNS R T， CHU L. Effect of capillary pressure on phase behavior in tight rocks and shales［J］. SPE Reservoir Evaluation & Engineering， 2013， 16（3）： 281⁃289.
[20]	SANDOVAL D， YAN W， MICHELSEN M L， et al. Phase envelop calculations for reservoir fluids in the presence of capillary pressure［C］//SPE Annual Technical Conference and Exhibition. Houston： Society of Petroleum Engineers， 2015： SPE⁃175110⁃MS.
[21]	ZARRAGOICOECHEA G J， KUZ V A. Critical shift of a confined fluid in a nanopore［J］. Fluid Phase Equilibria， 2004， 220（1）： 7⁃9.
[22]	ZHANG K Q， JIA N， LI S Y， et al. Static and dynamic behavior of CO₂ enhanced oil recovery in shale reservoirs： Experimental nanofluidics and theoretical models with dual⁃scale nanopores［J］. Applied Energy， 2019， 255： 113752.
[23]	YANG G， FAN Z Q， LI X L. Determination of confined fluid phase behavior using extended peng⁃robinson equation of state［J］. Chemical Engineering Journal， 2019， 378： 122032.
[24]	SONG Z J， SONG Y L， GUO J， et al. Adsorption induced critical shifts of confined fluids in shale nanopores［J］. Chemical Engineering Journal， 2020， 385： 123837.
[25]	PENG D Y， ROBINSON D B. A new two⁃constant equation of state［J］. Industrial & Engineering Chemistry Fundamentals， 1976， 15（1）： 59⁃64.
[26]	ABUDOUR A M， MOHAMMAD S A， ROBINSON R L， Jr， et al. Volume⁃translated peng⁃robinson equation of state for liquid densities of diverse binary mixtures［J］. Fluid Phase Equilibria， 2013， 349： 37⁃55.
[27]	魏兵，钟梦颖，赵金洲，等. 微⁃纳米受限空间原油⁃天然气最小混相压力预测方法［J］. 石油学报， 2022， 43（11）： 1604⁃1613.
	WEI B， ZHONG M Y， ZHAO J Z， et al. Prediction method for the minimum miscibility pressure of crude oil and natural gas in micro⁃nano confined space［J］. Acta Petrolei Sinica， 2022， 43（11）： 1604⁃1613.
[28]	Ponec V. Physical chemistry of surfaces， fifth edition. A. W. Adamson. John Wiley & Sons， Chichester， 1990. Ⅸ + 777 pp.， £47.50. ISBN 0⁃471⁃61019⁃4［J］. Recueil des Travaux Chimiques des Pays⁃Bas， 1991， 110（4）： 137.
[29]	WEINAUG C F， KATZ D L. Surface tensions of methane⁃propane mixtures［J］. Industrial and Engineering Chemistry， 1943， 35（2）： 239⁃246.
[30]	SIMONET R，BEHAR E. A modified redlich⁃kwong equation⁃of⁃state， application to general physical data calculations［J］.Chemical Engineering Science， 1976， 31（1）： 37⁃43.
[31]	RACHFORD H H， Jr， RICE J D. Procedure for use of electronic digital computers in calculation flash vaporization hydrocarbon equilibrium［J］. Journal of Petroleum Technology， 1952， 4（10）： 19⁃20.
[32]	SONG Y L， SONG Z J， FENG D， et al. Phase behavior of hydrocarbon mixture in shale nanopores considering the effect of adsorption and its induced critical shifts［J］. Industrial & Engineering Chemistry Research， 2020， 59（17）： 8374⁃8382.
[33]	AYIRALA S C， RAO D N. Comparative evaluation of a new gas/oil miscibility⁃determination technique［J］. Journal of Canadian Petroleum Technology， 2011， 50（9）： 71⁃81.
[34]	ZHANG Y， LASHGARI H R， DI Y， et al. Capillary pressure effect on phase behavior of CO₂/hydrocarbons in unconventional reservoirs［J］. Fuel， 2017， 197： 575⁃582.
[35]	ALHARTHY N S， TEKLU T W， NGUYEN T N， et al. Nanopore compositional modeling in unconventional shale reservoirs［J］. SPE Reservoir Evaluation & Engineering， 2016， 19（3）： 415⁃428.