2018-10-Offer for a Thesis Allowance Subject: Effect of organic nanoporosity on CO2 Geological sequestration from molecular and multi-scale simulations

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E2S: Energy and Environment Solutions

What is E2S UPPA?

What is E2S UPPA?

The consortium at the heart of the Energy Environment Solutions (E2S) project is a composed of the University of Pau and the Pays de l’Adour (UPPA) and two national research organisations, National Institute...

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  • > Offer for a Thesis Allowance Subject: Effect of organic nanoporosity on CO2 Geological sequestration from molecular and multi-scale simulations

Offer for a Thesis AllowanceSubject: Effect of organic nanoporosity on CO2 Geological sequestration from molecular and multi-scale simulations

Thesis subject

The central characteristic underlying CO2 geological sequestration is the large adsorption capacity of organic source rocks. This is mainly due to the coal matrix (coalbed reservoirs) or kerogen (shales’ reservoirs), the bulk constituant of the unconventionnal reservoirs considered for CO2 sequestration. Indeed, this phase, mainly composed of carbon, is nanoporous with a large pore surface to volume ratio because of the large presence of an amorphous and microporous phase (pore size < 2 nm). The fluids (hydrocarbon, CO2) adsorbed in such materials are subject to strong adsorption effects altering drastically their thermophysical properties compared to their bulk states. The solid-­fluid couplings cannot be neglected in this case and can be for instance responsible of the swelling of coal samples upon adsorption of CO2. If we start to have a better understanding of ultra-­confined fluids’ transport properties, the precise influence of solid-­fluid couplings on equilibrium and non-­equilibrium transport properties remains to be discovered (swelling, phonon effects).

This PhD project is meant for the use and the development of multi-­scale numerical methods such
as Molecular Dynamics, Monte-­Carlo simulations and classical Density Functional Theory to build realistic transport models accounting for solid-­fluid couplings both in the micro-­ and meso-­porosity. Ultimately, these results will be used in the framework of reservoir scale modeling.


Key words: CO2 sequestration, molecular simulations, multi-­‐scale transport, solid-­‐fluid coupling, microporous carbons


Working conditions

Hosting laboratory: Laboratoire des Fuides Complexes et leurs Réservoirs (LFCR, UMR 5150)                                                                                                                                   

PhD Director: Guillaume Galliero
PhD co-director: Amaël Obliger
PhD co-advisor: Christelle Miqueu

Localisation address: LFCR, Bldg. UFR Sciences et Techniques,Université de Pau et des Pays de l’Adour, campus of Pau, Pyrénées-Atlantiques, France

Starting date: Beginning 2019

Length: 3 years

Employer: Université de Pau et des Pays de l’Adour (UPPA)
Funding: E2S UPPA

Gross monthly salary: 1878 €
(UPPA doctoral contract, according to E2S UPPA project, including 96h of teaching during the three years)

The Laboratory of Complex Fluids and their Reservoirs (LFCR) develops a know-­‐how combining physical and interface chemistry, geomechanics, geophysics, reservoir geology and thermodynamics. The LFCR has the status of an "industrial" UMR with the company TOTAL as supporting organization in addition to the CNRS and the UPPA, which is positioned mainly around the study of fossil geo-­‐resources following themes totally in phase with the local socio-­‐economic environment. The student will work in the Thermophysical Properties team.


Missions - principal activities

I. Scientific Context
The specific structure and texture of the organic matter of geological reservoirs at the nanoscale is highly dependent on its origin and thermal history. Thanks to recent experimental and numerical techniques, we now start to have access to morphological and textural informations at the micro- and meso-scopic scales of the bulk organic matter. Realistic atomistic representations of  this microporous phase from various shale plays can be obtained by Molecular Dynamics simulations [1,2]. Images of mesopores scattered inside the microporous matrix from Transmission Electron Microscopy with a subnanometric resolution (~0.4 nm) have been recently made possible. For now, molecular dynamics studies of transport and adsorption in microporous carbons have always been carried out by assuming that adsorption induced swelling is negligible (constant volume and fixed atoms), and the dynamics of desorption-adsorption are not yet investigated.

In the past few years, equilibrium and out-of-equilibrium Molecular Dynamics simulations of transport in kerogen have been performed in the context of shale gas recovery from unconventional reservoirs showing that the usual Darcy’s law is not valid due to strong confinement effects [3,4,5,6]. Although, despite the apparent complexity of the microporous matrices, severe confinement effects (pore size below 2 nm) controlled by the porosity of the various kerogens allow hydrocarbon transport to be studied only via the self-diffusion coefficients of the species [3,4] even in the case of alkanes’ mixtures [5]. The decrease of the transport coefficients with the amount of adsorbed fluid can be in these cases described by a free volume theory independently of the nature of the mixture (number of components, composition) [5,6].

Because the organic matter of unconventional reservoirs is not homogeneously composed of a single microporous phase, the influence of the mesoporosity distributed the microporous matrix should be accounted for in transport models. Transmission Electron Microscopy (TEM) imaging have provided us with three-dimensional tomograms indicating that mesopores are scarcely distributed within the microporous matrix. By means of Continuous Time Random Walk (CTRW) simulations in these tomograms, we are able  to assess the adsorption effects in a simplistic fashion between the micro- and meso-porous phases on diffusion. An analytical model for the homogenized diffusion coefficient as function of the ratio of diffusion coefficients and concentrations in both phases can be built. The adsorbed fluid in the mesoporosity (pore size < 50 nm) has been considered as bulk fluid, which represents a key assumption that will need to be removed in the future since fluid can be highly structured under nanoscale confinement [7].

Understanding the fundamental mechanisms at play at the microscopic scales of geological reservoirs could pave the way for realistic predictions in the contexts of enhanced oil recovery and CO2 geological sequestration. More broadly, transport mechanisms in amorphous carbon structures are also of importance in the fields of filtration/separation, batteries and supercapacitors.

 II. Objectives
The PhD student will first have to perform atomistic simulations, Molecular Dynamics (MD) and Monte-Carlo (MC) simulations, of adsorption and transport of CO2 in bulk microporous carbon structures while accounting for the flexibility of the carbon matrix with the use of an appropriate atomistic force field. One major goal of this part of the PhD will be to unravel the precise link between diffusion and carbon matrices’ mechanical properties.

Then, the transport properties will be upscaled by integrating the effect of mesoporosity (connected or not). The PhD student will have to build a strategy using grid-based method (Non-Local DFT, CTRW) to account for both, the transport properties in the microporous matrix and the fluid structure in the mesoporosity. The implementation of such a strategy will have to be tested against MD simulations in simple rigid systems involving both porous phases. From there, realistic geometries, mixture transport and extension to swelling could be considered.

III. References

[1] J. Collell et al., Energy and Fuels, 28(12):7457–66, 2014.
[2] C. Bousige et al., Nature materials, 15, 576, 2016.
[3] K. Falk et al., Nature Communications, 6:6949, 2015.
[4] J. Collell et al., Journal of Physical Chemistry C, 119(39):22587–95, 2015.
[5] A. Obliger et al., Journal of Physical Chemistry Letters, pp. 3712–3717, 2016.
[6] A. Obliger et al., Nano Letters, 18(2):832–7, 2018.
[7] C. Malheiro et al., The Journal of Chemical Physics, 140(13):134707, 2014.


Required skills and competences

- Master’s degree in chemical engineering, chemical physics or physics.
- Experience with numerical modeling of transport properties and/or atomistic simulation is an advantage.


Application - Evaluation criteria

Application file assessment: Selection committee

Candidates will first be selected based on their application file.
Selected candidates will be contacted by mail.
Those selected after this first step, will then be interviewed.

Application files will be evaluated based on the following criteria:

  • Candidate's motivation, scientific maturity and curiosity
  • Candidate's knowledge in transport/diffusion and statistical physics
  • Grades and ranking during both your undergratuate studies and your Master degree, steadiness in your academic background
  • English language proficiency
  • Candidate’s ability to present her/his work and results


Application file composition and submission deadline

Application will include: (in a single pdf file)

  • CV
  • Cover letter detailing the candidate's motivations
  • Candidate's undergraduate and Master grade transcripts and ranking
  • Reference letter
  • Contact details of at least two people, from you work environment, who can be contacted for further reference

Applications must be sent to the following email addresse with the title “Doctoral application”: 
Amaël Obliger: amael.obliger @ gmail.com

For more details, please visit our websites: http://e2s-uppa.eu/en/index.html

Submission deadline : January 1st, 2019