Simultaneous Description of Equilibrium, Interfacial, and Transport Properties of Fluids Using a Mie Chain Coarse-Grained Force Field

Hoang, Hai; Delage-Santacreu, Stéphanie; Galliéro, Guillaume

doi:10.1021/acs.iecr.7b01397

Cited by 41 publications

(30 citation statements)

References 103 publications

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“…The transcription of the properties of the pseudo-component into molecular models used in molecular dynamics has been achieved using a top-down strategy based on the corresponding states, similarly to what done in ref. [16]. More precisely, we have used the Lennard-Jones chains model to represent the pseudo-component in which the molecular parameters (: sphere diameter, : potential depth and N: number of segments) were adjusted so as to yield exactly the critical temperature and the critical pressure, except for CO2.…”

Section: Parameterisation Of the Studied Systemmentioning

confidence: 99%

Linking up pressure, chemical potential and thermal gradients

2019

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Petroleum reservoirs are remarkable illustrations of the impact of a thermal gradient on fluid pressure and composition. This topic has been extensively studied during the last decades to build tools that are required by reservoir engineers to populate their models. However, one can get only a very limited number of representative samples from a given reservoir and assessing connectivity between all sampling points is often a key issue. In some extreme cases, the whole reservoir fluid properties must be derived from a single point to define the field development plan. To do so, available models are usually not satisfactory as they need too many parameters and so cannot be considered as predictive tools. We propose in this work a comprehensive approach based on the irreversible thermodynamics principles to derive the relationships between pressure, chemical potentials and thermal gradients in porous media. It appears that there is no need for additional assumptions, it is just a matter of a making the right choices along theoretical developments. One of the most important steps is to express the full pressure gradient. As a final result, we obtain the chemical potential gradients for all components of the mixtures that can be easily translated in term of compositions through Equation of State modelling. The most important features of the final expressions are: (i) the species relative separation in a thermal field is sensitive to the relative diffusion coefficients at stationary state. In porous media, the separation is sensitive to the permeability when the overall mobility is similar to diffusive mobility; (ii) the magnitude of the separation depends on the residual entropy of the species; (iii) the separation is not simply balanced by the average residual entropy. The balance is modified by the relative diffusion mobility of the components; (iv) in low permeability porous media, the thermal gradient induces a pressure gradient proportional to the fluid residual entropy. As a validation, the proposed approach has been applied on a reservoir fluid subjected to a geothermal gradient and compared with non-equilibrium molecular dynamics simulation results at the stationary state.

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Section: Parameterisation Of the Studied Systemmentioning

confidence: 99%

Linking up pressure, chemical potential and thermal gradients

2019

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“…A common explanation for this result is the assumption that by integrating out the atomistic features CG models are incapable of reproducing viscosities. Recent manuscripts challenge this vision [26,27], noting that appropriately parametrized CG models can correctly represent both volumetric and transport properties. If the results of our model are scaled to the lowpressure data point, the results of the Mie model become quantitative in nature, as the slope of both the simulation and the experiments agree (c.f.…”

Section: Final Commentsmentioning

confidence: 99%

Predicting the pressure dependence of the viscosity of 2,2,4-trimethylhexane using the SAFT coarse-grained force field

Zheng

Trusler

Bresme

et al. 2019

Fluid Phase Equilibria

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This work is framed within AIChE's 10 th Industrial Fluid Properties Simulation Challenge, with the aim of assessing the capability of molecular simulation methods and force fields to accurately predict the pressure dependence of the shear viscosity of 2,2,4-trimethylhexane at 293.15 K (20 °C) at pressures up to 1 GPa. In our entry for the challenge, we employ coarsegrained intermolecular models parametrized via a top-down technique where an accurate equation of state is used to link the experimentally-observed macroscopic volumetric properties of fluids to the force-field parameters. The state-of-the-art version of the statistical associating fluid theory (SAFT) for potentials of variable range as reformulated in the Mie incarnation is employed here. The potentials are used as predicted by the theory, with no fitting to viscosity data. Viscosities are calculated by molecular dynamics (MD) employing two independent methods; an equilibrium-based procedure based on the analysis of the pressure fluctuations through a Green-Kubo formulation and a non-equilibrium method where periodic perturbations of the boundary conditions are employed to simulate experimental shear stress conditions. There is an indication that, at higher pressures, the model predicts a solid phase (freezing) which we believe to be an artefact of the simplified molecular geometry used in the modelling. A comparison (made after disclosure of the experimental data) show that the model consistently underpredicts the viscosity by about 30%, but follows the pressure dependency accurately.

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“…The Mie chain coarse-grained (MCCG) force field has been used to model the noble gases (Helium, Neon, Argon, Krypton and Xenon) and n-alkane molecules (methane and n-hexane), as it has shown a good capability to describe thermophysical properties of these species [21][22][23]. The MCCG model consists in a simple homo-nuclear chain composed of N particles which are freely and tangentially bonded.…”

Section: Fluid Modelsmentioning

confidence: 99%

Elemental and isotopic fractionation of noble gases in gas and oil under reservoir conditions: Impact of thermodiffusion⋆

et al. 2019

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Noble gases, and the way they fractionate, is a promising approach to better constrain origin, migration and initial state distributions of fluids in gas and oil reservoirs. Thermodiffusion, is one of the phenomena that may lead to isotope and elemental fractionation of noble gases. However, this effect, assumed to be small, has not been quantified, nor measured, in oil and gas under reservoir conditions. Thus, in this work, molecular dynamics simulations have been performed to compute the thermal diffusion factors of noble gases, in a dense gas (methane) and in an oil (n-hexane) under high pressures. Interestingly, it has been found that thermal diffusion factors, associated to both isotopic ( 36 Ar, 40 Ar) and elemental fractionations of noble gases ( 4 He, 20 Ne, 40 Ar, 84 Kr and 131 Xe) in gas and oil, could be expressed as linear functions of the reduced masses. Regarding the amplitude of the phenomena, it has been found that, in a stationary 1D oil or gas fluid column, thermodiffusion due to a typical geothermal gradient has an impact on noble gas isotopic and elemental fractionation which is of the same order of magnitude than gravity segregation, but opposite in sign. In addition, the relative impact of thermodiffusion on isotopic and elemental fractionations depends on the fluid type which is another interesting feature. Thus, these first numerical results on isotopic and elemental fractionation of noble gases by thermodiffusion in simple pure gas and oil emphasize their interest as natural tracers that could be used to improve the pre-exploitation description of oil and gas reservoirs.

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Simultaneous Description of Equilibrium, Interfacial, and Transport Properties of Fluids Using a Mie Chain Coarse-Grained Force Field

Cited by 41 publications

References 103 publications

Linking up pressure, chemical potential and thermal gradients

Linking up pressure, chemical potential and thermal gradients

Predicting the pressure dependence of the viscosity of 2,2,4-trimethylhexane using the SAFT coarse-grained force field

Elemental and isotopic fractionation of noble gases in gas and oil under reservoir conditions: Impact of thermodiffusion⋆

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