CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids

Pau, France

CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids

Pau, France
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Broseta D.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Tonnet N.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Shah V.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Shah V.,Total S.A.
Geofluids | Year: 2012

The various modes of acid gas storage in aquifers, namely structural, residual, and local capillary trapping, are effective only if the rock remains water-wet. This paper reports an evaluation, by means of the captive-bubble method, of the water-wet character in presence of dense acid gases (CO 2, H 2S) of typical rock-forming minerals such as mica, quartz, calcite, and of a carbonate-rich rock sampled from the caprock of a CO 2 storage reservoir in the South-West of France. The method, which is improved from that previously implemented with similar systems by Chiquet et al. (Geofluids 2007; 7: 112), allows the advancing and receding contact angles, as well as the adhesion behavior of the acid gas on the mineral substrate, to be evaluated over a large range of temperatures (up to 140°C), pressures (up to 150bar), and brine salinities (up to NaCl saturation) representative of various geological storage conditions. The water-receding (or gas-advancing) angle that controls structural and local capillary trapping is observed to be not significantly altered in the presence of dense CO 2 or H 2S. In contrast, some alteration of the water-advancing (or gas-receding) angle involved in residual trapping is observed, along with acid gas adhesion, particularly on mica. A spectacular wettability reversal is even observed with mica and liquid H 2S. These results complement other recent observations on similar systems and present analogies with the wetting behavior of crude oil/brine/mineral systems, which has been thoroughly studied over the past decades. An insight is given into the interfacial forces that govern wettability in acid gas-bearing aquifers, and the consequences for acid gas geological storage are discussed along with open questions for future work. © 2012 Blackwell Publishing Ltd.

Petitfrere M.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Petitfrere M.,Total S.A. | Nichita D.V.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
Fluid Phase Equilibria | Year: 2014

Multiphase flash calculations and phase stability analysis are central in compositional reservoir and chemical process simulators. For instance, in some simulations, a huge amount of phase equilibrium calculations is required (the most important part of the computational effort). Moreover, a single failure may cause significant error propagations leading to false solutions. Thus, it is imperative that calculation algorithms are efficient and highly robust. The most difficult regions in mixture phase envelopes are in the vicinity of singularities: critical points for flash calculations and the stability test limit locus for stability analysis. For these conditions, all algorithms have difficulties to converge. Traditionally, a number of successive substitution iterations (SSI) are performed before switching to the second-order Newton method (many SSI iteration may be required before switch very close to singularities). The Trust-Region method has the advantage of performing a Newton step whenever the Hessian is definite positive; otherwise, the Trust-Region corrects the Hessian matrix by adding a diagonal element to make it positive definite, thus a descent direction is guaranteed. The Trust-Region limits the solution within a trust-radius, which is updated automatically at each iteration level, depending on the quality of the quadratic approximation. If the function is convex, the trust-radius enables larger changes in iteration variables, otherwise restricted steps are used to ensure a progress towards the solution. The proposed Trust-Region algorithm, as well as a hybrid methodology that combines SSI, Newton and Trust-Region steps, are tested for multiphase flash calculations and stability analysis on a variety of mixtures involving hydrocarbon components, carbon dioxide and hydrogen sulfide, exhibiting complicated phase envelopes. The proposed method compares favorably to the widely used SSI-Newton methods with various independent variables. The more difficult a test point is, the more spectacular the algorithm acts from both efficiency and reliability perspectives. © 2013 Elsevier B.V.

Hastie W.W.,University of KwaZulu - Natal | Watkeys M.K.,University of KwaZulu - Natal | Aubourg C.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
Gondwana Research | Year: 2014

The ~. 183. Ma old Karoo Large Igneous Province extends across southern Africa and is related to magmatism in Antarctica (west Dronning Maud Land and Transantarctic Mountains) and parts of Australasia. Intrusive events, including the emplacement of at least ten dyke swarms, occurred between ~. 183. Ma and ~. 174. Ma. We review here the field evidence, structure and geochronology of the dyke swarms and related magmatism as it relates to melt sources and the mantle plume hypothesis for the Karoo LIP. Specifically, the magma flow-related fabric(s) in 90 dykes from five of these swarms is reviewed, paying particular attention to those that converge on triple junctions in southern Africa and Antarctica. The northern Lebombo and Rooi Rand dyke swarms form an integral part of the Lebombo monocline, which converges upon the Karoo triple junction at Mwenezi, southern Zimbabwe. Dykes of the Northern Lebombo dyke swarm (182-178. Ma) appear to have initially intruded vertically, followed later by lateral flow in the youngest dykes. In dykes of the Okavango dyke swarm (178. Ma) there is evidence of steep magma flow proximal to the triple junction, and lateral flow from the southeast to the northwest in the distal regions. This is consistent with the Karoo triple junction and the shallow mantle being a viable magma source for both these dyke swarms. In the Rooi Rand dyke swarm (174. Ma) there is also evidence of vertical and inclined magma flow from north to south. This flow direction cannot be reconciled with the Karoo triple junction, as the northern termination of the Rooi Rand dyke swarm is in east-central Swaziland. The Jutulrøra and Straumsvola dyke swarms of Dronning Maud Land display evidence of sub-vertical magma flow in the north and lateral flow further south. The regional pattern of magma flow is therefore not compatible with direction expected from the Weddell Sea triple junction. The overall flow pattern in Karoo dykes is consistent with the triple junction being an important magma source. However, the Limpopo Belt and Kaapvaal Craton have significantly controlled the structure and distribution of the Lebombo and Save-Limpopo monoclines and the Okavango dyke swarm. The locus of magma flow in dykes of Dronning Maud Land is at least 500. km from the Karoo triple junction, as is the apparent locus for the Rooi Rand dyke swarm. In comparison with recent modelling of continental assembly, the structure and flow of the dyke swarms, linked with geochronology and geochemistry, suggests that thermal incubation during Gondwana assembly led to Karoo magmatism. A plate tectonic, rather than a fluid dynamic plume explanation, is most reasonably applicable to the development of the Karoo LIP which does not bear evidence of a deep-seated, plume source. © 2013 International Association for Gondwana Research.

Galliero G.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

Using nonequilibrium molecular dynamics simulations on simple Lennard-Jones binary mixtures, we have studied the behavior of planar fluid-fluid interfaces undergoing shear flow. When the miscibility is low enough, a slip together with a partial depletion have been noticed at the interface between the two fluid phases. The slip length can reach a value equal to some molecular diameters and the corresponding interfacial viscosity can be two times smaller than the value in the bulk. It is shown how the omission of this slip may lead to flow-rate misevaluation when dealing with a multiphase flow in a nanoporous medium even for non polymer fluids. In addition, using the simulation results, a simple relation between interfacial tension and interfacial viscosity is proposed for the monoatomic systems studied in this work. Finally, it is shown that the interfacial viscosity cannot be fully accounted for by estimating the local viscosity deduced from the local thermodynamic properties of the interface. © 2010 The American Physical Society.

Nichita D.V.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
Fluid Phase Equilibria | Year: 2016

The phase stability analysis problem is highly important in phase equilibrium calculations. The stability test limit locus (STLL) is an important underlying property of multi-component system phase diagrams, because in its vicinity the number of iterations for phase stability testing dramatically increases and divergence may occur. The cause of convergence problems in phase stability calculations, as well as of the existence of a discontinuity of the TPD function in the single-phase state, is the topology of the TPD surface. At the STLL, the stationary point of the TPD function is a saddle point (the Hessian is indefinite), and for pressures just above the STLL the Hessian matrix is ill-conditioned in a domain of the hyperspace that must be "crossed" by iterates starting from one of the initial guesses. This makes stability testing in the vicinity of the STLL really challenging, and any algorithm will experience difficulties in this (fortunately tiny in most cases) region. A change of variables would not eliminate this problem, since the TPD function in the new hyperspace inherits certain properties from the original one. In this work we propose a modified objective function which exhibits multiple global minima corresponding to the stationary points of the original (TPD) function. The highly desirable feature of the modified objective functions is that the Hessian matrix is positive definite in the vicinity of the STLL (the nature of the singularity is changed). One additional derivative level is required for minimizing the new objective function, but a normal termination of the iterative sequence in a reasonable number of iterations is worth this effort. The minimization is performed by a quasi-Newton BFGS method with line search, using a suitable change of variables which avoids improper scaling, as well as by Newton iterations. Criteria to switch from the original TPD formulation to the new one are required, since the use of the more complex formulation is justified only near the STLL. Results show how application of the proposed stability testing method for a number of typical extremely difficult situations ensures convergence within tens of iterations, while all other iterative methods for minimizing the TPD function are extremely slow, unstable or even divergent. © 2016 Elsevier B.V.

Duchateau C.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Broseta D.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
Advances in Water Resources | Year: 2012

It is well known that most inorganic electrolytes dissolved in water have the effect to raise the interfacial tension (IFT), whereas all compressed gases but helium have the opposite effect, which corresponds respectively to negative adsorption (depletion) of the salt and to gas adsorption on the two opposite sides of the interface. By using Gibbs' adsorption equation and reasonable assumptions, we show that those two effects are independent: the presence of inorganic electrolytes in the aqueous phase has a negligible impact on the gas-related IFT decrement, and the compressed gas does not in turn alter the IFT increment due to the salt dissolved in the aqueous phase. As a consequence the IFT at a given pressure and temperature can be approximated by the brine surface tension at the same temperature, minus the gas-related IFT decrement of pure water surface tension at those pressure and temperature. The two latter quantities are easier to determine experimentally, and have been the subject of numerous experimental and theoretical investigations. The proposed approximation is consistent with the available experimental data, including when the 'gas' is a supercritical fluid or a compressible condensate (liquid) made up of compounds sparingly soluble in water, such as CO 2 at respectively supercritical or subcritical temperatures. © 2012 Elsevier Ltd.

Hoang H.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Galliero G.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
Journal of Physics Condensed Matter | Year: 2013

This work aims at providing a tractable approach to model the local shear viscosity of strongly inhomogeneous dense fluids composed of spherical molecules, in which the density variations occur on molecular distance. The proposed scheme, which relies on the local density average model, has been applied to the quasi-hard-sphere, the Week-Chandler-Andersen and the Lennard-Jones fluids. A weight function has been developed to deal with the hard-sphere fluid given the specificities of momentum exchange. To extend the approach to the smoothly repulsive potential, we have taken into account that the non-local contributions to the viscosity due to the interactions of particles separated by a given distance are temperature dependent. Then, using a simple perturbation scheme, the approach is extended to the Lennard-Jones fluids. It is shown that the viscosity profiles of inhomogeneous dense fluids deduced from this approach are consistent with those directly computed by non-equilibrium molecular dynamics simulations. © 2013 IOP Publishing Ltd.

Hoang H.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Galliero G.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

In this paper, molecular dynamics simulations of a simple Lennard-Jones fluid confined in narrow slit pores and undergoing shear have been performed. The aim is to investigate the effects of density inhomogeneities at the fluid-solid interfaces on the shear viscosity profiles. It has been found that the local viscosity was varying strongly with the distance from the solid walls for both dilute and dense fluid states with oscillations correlated to the density ones. To describe the computed viscosity profiles, we propose a scheme that uses the local average density model, combined with an adequate weight function, for the configurational viscosity and a semiempirical model for the translational viscosity. It is shown that the proposed approach is able to provide viscosity profiles in good agreement with those coming from simulations for different pore widths and for different fluid states (dilute to dense). © 2012 American Physical Society.

Nichita D.V.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Graciaa A.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
Fluid Phase Equilibria | Year: 2011

Phase equilibrium calculations require the most important computational effort in many process simulators and in reservoir compositional simulations. In this work, a new reduction method for phase equilibrium calculations is proposed. A new set of independent variables (and the related set of error equations) is introduced, based on the observation that, under certain conditions, the equilibrium ratios can be related only to some component properties (elements of the reduction matrix) and to equation of state parameters. The new formulation leads to simpler expressions of the elements of the Jacobian matrix. Some important features are presented, and an interesting and useful link with classical flash calculation methods is revealed. The reliability and efficiency of the proposed method are tested on several synthetic and reservoir hydrocarbon mixtures. The proposed method proves to be robust and it performs in all cases better than previous reduction methods. Finally, it is discussed how the new set of independent variables can be used for a variety of phase equilibrium calculations. © 2010 Elsevier B.V.

Vermorel R.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids | Pijaudier-Cabot G.,CNRS Laboratory of Thermodynamics and Energetics of Complex Fluids
European Journal of Mechanics, A/Solids | Year: 2014

Poromechanics offers a consistent theoretical framework for describing the mechanical response of porous solids fully or partially saturated with a fluid phase. When dealing with fully saturated microporous materials, which exhibit pores of the nanometer size, effects due to adsorption and confinement of the fluid molecules in the smallest pores must be accounted for. From the mechanical point of view, these phenomena result into volumetric deformations of the porous solid, the so-called "swelling" phenomenon. The present work investigates how the poromechanical theory may be refined in order to describe such adsorption and confinement induced effects in microporous solids. Poromechanics is revisited in the context of isotropic microporous materials with generic pore size distributions. The new formulation introduces an effective pore pressure, defined as a thermodynamic variable at the representative volume element scale (mesoscale), which is related to the overall mechanical work of the confined fluid. Accounting for the thermodynamic equilibrium of the system, we demonstrate that the effective pore pressure depends on macroscopic variables, such as the bulk fluid pressure, the temperature and the total and excess adsorbed quantity of fluid. As an illustrating example, we apply the model to compute strains and variations of porosity in the case of the methane and carbon dioxide sorption on coal. Agreement with experimental data found in the literature is observed. © 2013 Elsevier Masson SAS. All rights reserved.

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