Thermodynamic modeling of confined fluids using an extension of the generalized van der Waals theory

Travalloni, Leonardo; Castier, Marcelo; Tavares, Frederico W.; Sandler, Stanley I.

doi:10.1016/j.ces.2010.01.032

Cited by 141 publications

(107 citation statements)

References 25 publications

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“…S J X f (8) In our formulation, the pressures in both phases (P g , P l ) are the only variables that are not in a logarithmic scale. For a proper comparison in the sensitivities, the derivatives were converted to approximate the sensitivity in a logarithmic sense:…”

Section: ■ Methodsmentioning

confidence: 99%

The Phase Envelope of Multicomponent Mixtures in the Presence of a Capillary Pressure Difference

Sandoval

Yan

Michelsen

et al. 2016

Ind. Eng. Chem. Res.

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Confined fluids such as oil and gas mixtures inside tight reservoirs are systems that can experience high capillary pressure difference between the liquid and gas phases. This capillary pressure difference has an effect on the phase equilibrium and in some cases is considerably high. We presented an algorithm which can reliably compute the whole phase envelope for multicomponent mixtures when there is a capillary pressure difference. It uses an equation of state for the phase equilibrium and the Young−Laplace equation for the capillary pressure model. The algorithm proves to be robust and efficient for test mixtures with wide ranges of compositions at different capillary radii and vapor fractions. The calculation results show that the phase envelope changes everywhere except at the critical point. The bubble point and the lower branch of the dew point show a decrease in the saturation pressure, whereas the upper branch of the dew point shows an increase. The cricondentherm is shifted to a higher temperature. We also presented a mathematical analysis of the phase envelope shift due to capillary pressure based on linear approximations. The resulting linear approximation equations can predict the correct direction of the phase envelope shift. Combined with the multicomponent Clapeyron equation, the equations reveal why the shift changes direction for the saturation pressure at the cricondentherm and for the saturation temperature at the cricondenbar. The equations can be used to estimate the magnitude of shift, and the approximation is close for the change in the bubble point pressure.

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Section: ■ Methodsmentioning

confidence: 99%

The Phase Envelope of Multicomponent Mixtures in the Presence of a Capillary Pressure Difference

Sandoval

Yan

Michelsen

et al. 2016

Ind. Eng. Chem. Res.

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“…Zarragoicoechea and Kuz (2004) extended the van der Waals EoS to fluids confined in nanopores, assuming the walls were neutral and ignoring adsorption. Travalloni et al (2010) proposed a cubic EoS based on the generalized van der Waals theory to describe the behavior of pure fluids and mixtures confined in porous media. In the model, the fluid molecules were assumed spherical, interacting with each other and with the pore though square-well potentials.…”

Section: Introductionmentioning

confidence: 99%

Application of PC-SAFT Equation of State for CO2 Minimum Miscibility Pressure Prediction in Nanopores

Wang

Chen

2016

All Days

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CO 2 miscible injection is generally one of the most efficient enhanced oil recovery (EOR) methods and widely used in the conventional oil reservoirs. The applicability of CO 2 EOR technology for unlocking the resources from unconventional tight and shale formations and the mechanisms of miscible flooding in these reservoirs still remain unclear. An important parameter used to evaluate the feasibility of CO 2 miscible flooding is the minimum miscibility pressure (MMP). Even though experimental approaches, empirical correlations and theoretical methods have performed well in measuring or predicting MMP between CO 2 and crude oil in conventional reservoirs, they may not be suitable for unconventional formations as phase behavior and MMP can be significantly affected by confinement effect in small pores (e.g., nanopores) in such formations.In this study, a new MMP prediction model based on the modified Parachor Model associated with the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) is developed to determine CO 2 MMP both in the bulk phase and nanopores. The Parachor Model is modified to account for the confinement effect of nanopore walls on the equilibrium interfacial tension (IFT). The Equilibrium IFT reduction in nanopores is related to a temperature-dependent and slit pore width-dependent modification term. The parameters of the new Parachor Model are determined by matching the vapor-liquid surface tension values for CH 4 , C 2 H 6 , C 3 H 8 , n-C 4 H 10 , and n-C 8 H 18 in nanopores, respectively. The prediction ability of the new model is verified by comparing the predicted MMP in the bulk phase with the results of other theoretical approaches and slim-tube experimental data. Finally, the new model is applied to estimate the MMP between Bakken oil and CO 2 stream. The effect of temperature, slit pore width, and impure components in the injected CO 2 on the MMP are also studied. The newly developed model successfully reproduces MMP in bulk phase as compared with both other methods and experimental data. The overall average absolute relative deviation (AARD) for MMP is within 8 %. The calculated equilibrium IFT for liquid-vapor phase has a good agreement with molecular simulation results. For Bakken oil-CO 2 system, if the slit pore width is larger than 10 nm, MMP is independent on pore width; otherwise, it decreases significantly with the decrease of the pore width. If pore width decreases to 3 nm, 67.5 % decrease in the IFT is observed and 23.5% reduction is achieved for MMP between Bakken oil and CO 2 stream, indicating that it is easier to reach miscibility in nanopores, and CO 2 miscible flooding might be a promising enhanced oil recovery (EOR) technology for tight oil and shale oil reservoirs. Furthermore, MMP increases with an increase of temperature in bulk phase, whereas IFT and MMP decrease with an increase of temperature in nanopores.

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“…• Equation of state Kuz (2002 and2004), Derouane (2007), Travalloni et al (2010a and2010b) and Ma et al (2013)). …”

Section: Introductionmentioning

confidence: 99%

Modeling the Effects of Porous Media in Dry Gas and Liquid Rich Shale on Phase Behavior

Jamili

2014

All Days

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Because of the confinement effects in shale formations, fluid flow is different compared to conventional reservoirs. The interactions between the fluid molecules and porous wall inside nanopores play such an important role that can change the phase behavior of the fluids. The fluids in shale reservoirs are usually stored in two forms, free fluids and adsorbed fluids. The region where free fluids are stored has negligible fluid-wall interactions while the region for adsorbed fluids is under strong pore wall influence. The current available equations of state cannot capture the phase behavior of the adsorbed phase in porous media due to the ignorance of the fluid-wall interactions. This paper discussed the effects of the fluid-wall interactions on fluid phase behavior from a modeling of of view.The production from shale reservoirs in the US has shifted from gas windows to condensate windows and oil windows recently due to low natural gas price. Liquid-rich shales, such as Barnett, Eagle Ford, and Marcellus are brought more attentions than ever before. Thus, it is critical to understand the fluid phase behavior and properties and their impacts on production in the condensate systems. Our work focuses on the predictions of fluid critical property change and fluid density change inside nanoporous media. Simplified Local-Density theory for single component coupled with modified Peng-Robinson Equation of State was used to predict the density profiles of dry gas (pure methane) in confined pores. The model was then extended to mixtures for the study of condensate systems.Our results showed that due to the fluid-wall interactions, the fluid density is not uniformly distributed across the pore. The fluid density is higher near the wall than that in the center region of the pore. It also showed that depending on fluid types, temperature, pressure and pore sizes, the fluid density profile would change. The pore size range we focused on was from 2 nm to 10 nm. In order to present the condensate system, a synthetic mixture of 75% methane and 25% n-butane is used. It is found that fluid composition is not uniform across the pore. Heavier component (n-butane) tends to accumulate near the wall while lighter component (methane) would like to stay in the center region of the pore. For a 10 nm wide pore, the composition of n-butane of the synthetic mixture can be as high as 66% close to the pore wall.

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Thermodynamic modeling of confined fluids using an extension of the generalized van der Waals theory

Cited by 141 publications

References 25 publications

The Phase Envelope of Multicomponent Mixtures in the Presence of a Capillary Pressure Difference

The Phase Envelope of Multicomponent Mixtures in the Presence of a Capillary Pressure Difference

Application of PC-SAFT Equation of State for CO2 Minimum Miscibility Pressure Prediction in Nanopores

Modeling the Effects of Porous Media in Dry Gas and Liquid Rich Shale on Phase Behavior

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