Subcontinuum mass transport of condensed hydrocarbons in nanoporous media

Falk, Kerstin; Coasne, Benoît; Pellenq, Roland J.‐M.; Ulm, Franz‐Josef; Bocquet, Lydéric

doi:10.1038/ncomms7949

Cited by 270 publications

(331 citation statements)

References 41 publications

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“…Falk et al used molecular simulation and statistical mechanics to show the transmission behavior of hydrocarbon in shale nanoporous matrix, the results demonstrated that the Darcy's law fails to predict the transport of shale gas at the nanoscale. In particular, when studying on the transmission mechanism of shale gas in disordered pores, the influence of permeability, porosity and tortuosity should be considered [53]. It was found that whether the gas is adsorbed on coal or shale, the organics structure is the main research object.…”

Section: Introductionmentioning

confidence: 99%

Study on the Adsorption, Diffusion and Permeation Selectivity of Shale Gas in Organics

Wang

Liu

et al. 2017

Energies

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Abstract:As kerogen is the main organic component in shale, the adsorption capacity, diffusion and permeability of the gas in kerogen plays an important role in shale gas production. Based on the molecular model of type II kerogen, an organic nanoporous structure was established. The Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods were used to study the adsorption and diffusion capacity of mixed gas systems with different mole ratios of CO 2 and CH 4 in the foregoing nanoporous structure, and gas adsorption, isosteric heats of adsorption and self-diffusion coefficient were obtained. The selective permeation of gas components in the organic pores was further studied. The results show that CO 2 and CH 4 present physical adsorption in the organic nanopores. The adsorption capacity of CO 2 is larger than that of CH 4 in organic pores, but the self-diffusion coefficient of CH 4 in mixed gas is larger than that of CO 2 . Moreover, the self-diffusion coefficient in the horizontal direction is larger than that in the vertical direction. The mixed gas pressure and mole ratio have limited effects on the isosteric heat and the self-diffusion of CH 4 and CO 2 adsorption. Regarding the analysis of mixed gas selective permeation, it is concluded that the adsorption selectivity of CO 2 is larger than that of CH 4 in the organic nanopores. The larger the CO 2 /CH 4 mole ratio, the greater the adsorption and permeation selectivity of mixed gas in shale. The permeation process is mainly controlled by adsorption rather than diffusion. These results are expected to reveal the adsorption and diffusion mechanism of gas in shale organics, which has a great significance for further research.

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Section: Introductionmentioning

confidence: 99%

Study on the Adsorption, Diffusion and Permeation Selectivity of Shale Gas in Organics

Wang

Liu

et al. 2017

Energies

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“…Extracting the mass term directly from MD simulations paves the way to the study of isotopic effects. It can also be used to quantify in a well-defined way the number of molecules brought along ions during transport or to interpret the peculiar behaviour of the friction on alcanes as a function of chain length [29,30]. In particular, it provides a microscopic route to model acoustophoresis [31,32] or electro-osmotic effects [33,34].…”

Section: Figmentioning

confidence: 99%

Molecular Hydrodynamics from Memory Kernels

et al. 2016

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The memory kernel for a tagged particle in a fluid, computed from molecular dynamics simulations, decays algebraically as t −3/2 . We show how the hydrodynamic Basset-Boussinesq force naturally emerges from this long-time tail and generalize the concept of hydrodynamic added mass. This mass term is negative in the present case of a molecular solute, at odds with incompressible hydrodynamics predictions. We finally discuss the various contributions to the friction, the associated time scales and the cross-over between the molecular and hydrodynamic regimes upon increasing the solute radius.The Brownian motion of a particle in a fluid finds its origin in the fluctuating force exerted by the solvent molecules on the solute. It has long been known that the canonical description of this random force by a Gaussian Markov process is only valid in limiting cases. Even in the limit where the solute is much heavier than the solvent particles, for which multiple time-scale analysis allows to recover the Smoluchowski equation for diffusion [1], nonMarkovian effects are expected when the mass density ratio is close to unity [2] -a situation which is rather the rule than the exception e.g. in colloidal suspensions. These non-Markovian effects arise because of momentum conservation, leading to slow hydrodynamic modes that manifest themselves as long-time tails in the velocity autocorrelation function (VACF) [3][4][5][6]. Recent experiments have demonstrated that the force exerted by the bath includes a deterministic component [7], well described for large colloidal spheres by the Basset-Boussinesq (BB) hydrodynamic force [8,9]:where R is the sphere radius, η the solvent viscosity and ρ 0 its mass density. The first term is the usual Stokes friction. The other two account for the inertia of the displaced fluid and involve a finite added mass m BB 0 = 2 3 πR 3 ρ 0 and a viscosity-dependent retarded component describing the transient effects of momentum diffusion in the solvent. While continuous descriptions of steady-state flows appear to hold down to the nanoscale [10][11][12], possibly at the price of adapting the hydrodynamic radius R or the boundary conditions [13], their validity for the transient regimes should be questioned. The implicit assumption of a separation of time scales between the solvent and solute dynamics, which holds a priori for colloidal particles [14], is expected to break down with smaller solutes such as nanoparticles or biomolecules.Here we address the fundamental questions that arise when approaching the regime of molecular solutes by computing directly from Molecular Dynamics (MD) simulations the memory kernel and the random noise of the Generalized Langevin Equation (GLE). A novel algorithm based on the Mori-Zwanzig formalism with high numerical stability allows us to explore long time scales for the first time. We consider the extreme case of a tagged particle (identical masses and sizes) in a pure supercritical fluid.By examining the long-time behaviour of the memory kernel, we demonstrate the gen...

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“…However, different from water transport in micropores, the governing physics of water transport in nanopores become various boundary conditions (slip flow or multilayer sticking), caused by wettability, and viscosity variation in nanopores, caused by strong interactions from nanopore wall (Monteiro et al 2012;Falk et al 2015;Klein and Kumacheva 1995;Neto et al 2005). In this paper, an improved model was proposed based on Wu et al's work (2017).…”

Section: Introductionmentioning

confidence: 99%

Effect of critical thickness on nanoconfined water fluidity: review, communication, and inspiration

Sun

Yao

et al. 2018

J Petrol Explor Prod Technol

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It is crucial to precisely estimate the water transport behaviors in shale formation. However, the present study on this subject is quite limited. A comprehensive literature review is conducted and some improvements are proposed. In this paper, an improved model is proposed to investigate the flow of water in nanopores of shale formation. First, a quadratic equation is proposed to build the relationship between water viscosity and contact angle. Then, the effect of critical thickness on water transport behaviors is discussed. Results show that: (a) the flow enhancement is smaller than 1 when the contact angle is smaller than 100° due to energy barrier induced by strong hydrophilicity of the nanopore wall; (b) the flow enhancement becomes infinite when the contact angle is approaching 180°; and (c) the flow enhancement increases with decreasing of critical thickness, especially for hydrophilic nanopores (the contact angle is smaller than 120°) and nanopores with a relatively small diameter (smaller than 50 nm).

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Subcontinuum mass transport of condensed hydrocarbons in nanoporous media

Cited by 270 publications

References 41 publications

Study on the Adsorption, Diffusion and Permeation Selectivity of Shale Gas in Organics

Study on the Adsorption, Diffusion and Permeation Selectivity of Shale Gas in Organics

Molecular Hydrodynamics from Memory Kernels

Effect of critical thickness on nanoconfined water fluidity: review, communication, and inspiration

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