Journées Hydrates, Brest, 09‐13 septembre 2019

Journées “Hydrates”

09‐13 septembre 2019 IFREMER Pôle Numérique 305 Avenue Alexis de Rochon 29280 PLOUZANE

1 Journées Hydrates, Brest, 09‐13 septembre 2019

2 Journées Hydrates, Brest, 09‐13 septembre 2019

WELCOME

We are pleased to welcome you for the 2nd meeting of the French research consortium GdR2026 Hydrates at the University of Bordeaux. This event brings together leading experimental, theoretical, and computational scientists from among the unusually broad community of researchers interested in the various research areas of gas hydrates going from chemical and energy engineering to geosciences and astrophysics through physical‐ chemistry and thermodynamics. The issues addressed during this meeting concern major aspects of “hydrate sciences” such as hydrate/substrates interactions, thermodynamics, formation kinetics, cage occupancy and as well as formation at extreme conditions.

The workshop is divided into two parts. The first part is dedicated to meetings of french research consortiums working on a common project (ANR, EU, etc.) in closed session. The second part is the general meeting, gathering about 60 participants. Its scientific program contains about 31 presentations, including invited talks, oral contributions and poster presentations.

Organizing committee Livio Ruffine ‐ IFREMER, Brest Hélène Ondréas ‐ IFREMER, Brest Marie‐Odile Lamirault‐Gall ‐ IFREMER, Brest Alison Chalm‐ IFREMER, Brest Elisabeth Savoye ‐ IFREMER, Brest Olivia Fandino‐Torres – IFREMER, Brest Arnaud Desmedt, ISM CNRS ‐ Univ. Bordeaux Karine Ndiaye, ISM CNRS ‐ Univ. Bordeaux Audrey Bourgeois, ISM CNRS ‐ Univ. Bordeaux Daniel Broseta – LFC‐R UMR 5150 CNRS, Total, Univ. Pau

Scientific Committee Baptiste Bouillot ‐ LGF, UMR 5703 CNRS, Mines Saint‐Etienne Daniel Broseta – LFC‐R UMR 5150 CNRS, Total, Univ. Pau André Burnol – BRGM, Orléans Bertrand Chazallon ‐ PhLAM UMR8523 CNRS Univ. Lille Christophe Coquelet ‐ CTP, Mines ParisTech Anthony Delahaye ‐ Division des Génie des Procédés et Froid, IRSTEA, Antony Arnaud Desmedt ‐ ISM UMR5255 CNRS, Univ. Bordeaux Christophe Dicharry ‐ LFC‐R UMR5150 CNRS, Total, Univ. Pau Jean‐Michel Herri ‐ LGF, UMR 5703 CNRS, Mines Saint‐Etienne Sylvain Picaud ‐ UTINAM UMR6213 CNRS, Univ. Franche‐Comté Livio Ruffine ‐ IFREMER, Brest Anne Sinquin ‐ IFPEN Anh‐Minh Tang ‐ Laboratoire Navier UMR8205 CNRS, Ponts Paristech Gabriel Tobie ‐ LPG UMR6112 CNRS, Univ. Nantes

3 Journées Hydrates, Brest, 09‐13 septembre 2019

4 Journées Hydrates, Brest, 09‐13 septembre 2019

CONTENT

WELCOME ...... 3 DETAILED PROGRAM ...... 7 Lundi 9 septembre 2019 ...... 7 Mardi 10 septembre 2019 ...... 9 Mercredi 11 septembre 2019 ...... 11 Jeudi 12 septembre 2019 ...... 12 Vendredi 13 septembre 2019 ...... 12 LIST OF PARTICIPANTS ...... 13 LIST OF ABSTRACTS ...... 15 Gas‐hydrate Pockmarks in deep water Nigeria: formation, evolution and related hazards 17 Guest Trapping and Selectivity within mixed Clathrate Hydrates: a Grand Canonical Monte Carlo Study coupled with thermodynamic modelling ...... 18

How different formation pathways impact the structure and separation efficiency in CO2‐ N2 gas mixtures using TBAB Semi‐clathrate Hydrates ...... 19 Cascades of hydrate filaments promoted by a porous substrate, activated charcoal ...... 24 Mechanical homogenization of gas hydrate bearing soils ...... 27 Clathrate hydrate on planet Mars: at present time and in the past ...... 31 Clathrate hydrates in the icy worlds of the Solar system ...... 32

Stability of mixed CH4‐CO2‐N2 hydrates and mass transfer during gas exchange ...... 33 Investigation of the exchange kinetic between methane and carbon dioxide in gas hydrates: application to CO2 capture from flue gas analogs ...... 37 Gestion de la vapeur dans les boucles de refroidissement secondaire à hydrates de gaz .. 38 Flow loop experiments to study gas hydrate formation in gas‐water‐oil systems ...... 39 Modification of formation kinetics and of gas selectivity in “artificial” sedimentary gas hydrates thanks to silica nano/micro‐beads...... 40 Elastic parameters of hydrate‐bearing sands using DEM ...... 42 LIST OF POSTERS ...... 45

Quantitative study of CO2‐CH4 and N2‐CH4 mixed clathrate hydrates using gas chromatography, Raman and IR reflectance spectroscopy: Application to icy moons ...... 47 NOTES ...... 55

5 Journées Hydrates, Brest, 09‐13 septembre 2019

6 Journées Hydrates, Brest, 09‐13 septembre 2019

DETAILED PROGRAM

Lundi 9 septembre 2019

09:00 – 12:00 Réunions de projets

12:00 – 13:30 : Pause déjeuner

13:30 – 13:45 Accueil des participants et introduction

13:45 – 14:30 Plénière : N. Sultan “Gas hydrates pockmarks in deep water Nigeria: formation, evolution and related hazards”

14:30 – 15h50 : Session 1 : Etudes fondamentales des hydrates de gaz : de l’échelle moléculaire aux propriétés macroscopiques

14:30 Patt et al.: Guest Trapping and Selectivity within mixed Clathrate Hydrates: a Grand Canonical Monte Carlo Study coupled with thermodynamic modelling 14:50 Rodriguez et al.: How different formation pathways impact the structure and separation efficiency in CO2‐N2 gas mixtures using TBAB Semi‐clathrate Hydrates 15:10 Petuya et al.: Structural stability of CO clathrate hydrates using DFT calculations 15:30 Chabab et al.: Thermodynamic study of the phase equilibria in the gas‐water‐ (NaCl) systems using electrolyte CPA EoS

15:50 – 16:20 : Pause café

16:20 – 17h20 : Session 2 : Etudes fondamentales des hydrates de gaz : de l’échelle moléculaire aux propriétés macroscopiques

16:20 Atig et al.: Contactless measurement of the mechanical properties of methane hydrate at pore scales 16:40 Venet et al.: Cascades of hydrate filaments promoted by a porous substrate, activated charcoal 17:00 Le et al.: Grain ‐scale morphology and distribution of methane hydrates formed in sand sediment under excess gas conditions

7 Journées Hydrates, Brest, 09‐13 septembre 2019

17:20 – 19h30 : Session 3 : Posters, échanges et buffet

 Le Menn et al.: Quantitative study of CO2‐CH4 and N2‐CH4 mixed clathrate hydrates using gas chromatography, Raman and IR reflectance spectroscopy: Application to icy moons  Lemaire et al.: Influence of alkaline feldspars‐surrogates on the formation kinetic and the selectivity of CO2‐N2 mixed hydrates: investigation by neutron scattering and Raman spectroscopy  Espert et al.: Using quantum mechanics modeling for investigating the structural properties of strong acid hydrates  Bazinet et al.: Study of Methane Hydrate Formation in Fontainebleau Sand Using X‐Ray Computed Tomography: Methodological development

8 Journées Hydrates, Brest, 09‐13 septembre 2019

Mardi 10 septembre 2019

08:30 – 09:00 : Accueil café

09:00 – 09:45 Plénière : P. Le Mélinaire « Desalination using clathrate hydrate »

09:45 – 12h15 : Session 4 : Hydrates naturels : Géosciences et Planétologie

09:45 Garziglia et al.: Insights into the characterization of gas hydrate‐bearing sediments from in situ geotechnical and acoustic measurements 10:05 Alavoine et al.: Mechanical homogenization of gas hydrate bearing soils 10:25 Burnol et al.: GARAH: a GeoERA project addressing knowledge gaps to allow gas hydrate assessment of the European continental margin

10:45 – 11:15 : Pause café

11:15 Lemaire et al.: Influence of alkaline feldspars‐surrogates on the formation kinetic and the selectivity of CO2‐N2 mixed hydrates under astrophysical and geophysical conditions 11:35 Schmidt et al.: Clathrate hydrate on planet Mars: at present time and in the past 11:55 Tobie et al.: Clathrate hydrates in the icy worlds of the Solar system

12:15 – 14:00 : Pause déjeuner

14:45 – 17:00 : Plénière : P. Glennat « Hydrates & Production pétrolière »

09:45 – 12h15 : Session 5 : Procédés innovants

14:45 Legoix et al.: Stability of mixed CH4‐CO2‐N2 hydrates and mass transfer during gas exchange 15:05 Martinez‐Escandell et al.: High‐performance of gas hydrates confined in nanoporous solid for CH4 and CO2 storage 15:25 Le et al.: Investigation of the exchange kinetic between methane and carbon dioxide in gas hydrates: application to CO2 capture from flue gas analogs

15:45 – 16:00 : Pause café

9 Journées Hydrates, Brest, 09‐13 septembre 2019

16:00 Pons et al.: Gestion de la vapeur dans les boucles de refroidissement secondaire à hydrates de gaz 16:20 Almeida et al.: Flow loop experiments to study gas hydrate formation in gas‐ water‐oil systems 16:40 Bouillot et al.: « TITRE A VENIR »

17:00 – 17:45 : Table ronde autour des problématiques industrielles

19:00 : Dîner conférence

10 Journées Hydrates, Brest, 09‐13 septembre 2019

Mercredi 11 septembre 2019

08:30 – 09:00 : Accueil café

09:00 – 09:45 Plénière : H. Lu « TITRE A VENIR »

09:45 – 10h35 : Session 6 : Géosciences et Hydrates naturels

09:45 Métais et al.: Modification of formation kinetics and of gas selectivity in “artificial” sedimentary gas hydrates thanks to silica nano/micro‐beads 10:05 Benmesbah et al.: Etude cinétique et thermodynamique des hydrates de gaz en milieu poreux : applications aux hydrates sédimentaires et aux procédés de stockage du froid

10:25 – 11:00 : Pause café

11:00 Theocharis et al.: Elastic parameters of hydrate‐bearing sands using DEM 11:20 Riboulot et al.: Freshwater lake to salt‐water sea causing widespread hydrate dissociation in the Black Sea

11:40 – 12:00 Mot de clôture

12:00 : Fin des Journées Hydrates

12:30 – 16:00 Comité de Pilotage du GdR

11 Journées Hydrates, Brest, 09‐13 septembre 2019

Jeudi 12 septembre 2019

09:30 – 12:30 : Accueil des élèves d’établissements secondaires du Finistère (Vague 1) : Ateliers scientifiques de découverte des géosciences marines (Groupes 1, 2 et 3)

12:30 – 14:00 : Pause déjeuner

14:00 – 17:00 : Accueil des élèves d’établissements secondaires du Finistère (Vague 2) : Ateliers scientifiques de découverte des géosciences marines (Groupes 4, 5 et 6)

Vendredi 13 septembre 2019

09:30 – 12:30 : Accueil des élèves d’établissements primaires (Classes de CM1 / CM2) du Finistère Ateliers scientifiques de découverte des géosciences marines (Groupe 1, 2 et 3)

13:00 : Fin des Journées « Scolaires »

12 Journées Hydrates, Brest, 09‐13 septembre 2019

LIST OF PARTICIPANTS

 ABADIE Emilie, Total E&P CSTJF – Pau, France ([email protected])  ALAVOINE Axelle, École Nationale des Ponts et Chaussées – Marne‐la‐Vallée, France ([email protected])  ALMEIDA Vinicius, École des Mines de Saint‐Etienne – Saint‐Etienne, France (vinicius.de‐ [email protected])  ATIG Dyhia, Univ. de Pau et des Pays de l'Adour – Pau, France (dyhia.atig@univ‐pau.fr)  BAZINET Laurène, Ifremer Brest – Plouzané, France ([email protected])  BENMESBAH Fatima Doria, Ifremer/IRSTEA–Plouzané, France ([email protected])  BOUILLOT Baptiste, École des Mines de Saint‐Etienne – Saint‐Etienne, France ([email protected])  BOURGEOIS Lydie, ISM, Univ. de Bordeaux – Talence, France (lydie.bourgeois@u‐ bordeaux.fr)  BROSETA Daniel, LFC‐R, Univ. de Pau et des Pays de l'Adour – Pau, France (daniel.broseta@univ‐pau.fr)  BURNOL André, BRGM – Orléans, France ([email protected])  CHABAB Salaheddine, Ecole des Mines de Paritech, Paris – France (salaheddine.chabab@mines‐paritech.fr)  CHABOT Baptiste, École Nationale des Ponts et Chaussées – Marne‐la‐Vallée, France ([email protected])  CHAZALLON Bertrand, PhLAM, Univ. de Lille – Lille, France (bertrand.chazallon@univ‐lille.fr)  DE LAURE Emmanuel, École Nationale des Ponts et Chaussées – Marne‐la‐Vallée, France ([email protected])  DELAHAYE Anthony, Irstea – Antony, France ([email protected])  DESMEDT Arnaud, ISM, CNRS, Univ. Bordeaux – Talence, France (arnaud.desmedt@u‐ bordeaux.fr)  DESPLANCHE Sarah, ISM, Univ. de Bordeaux – Talence, France (sarah.desplanche@u‐ bordeaux.fr)  DICHARRY Christophe, LFCR, Univ. de Pau et des Pays de l'Adour – Pau, France (christophe.dicharry@univ‐pau.fr)  DONVAL Jean‐Pierre, Ifremer Brest – Plouzané, France ([email protected])  DUPRE Stéphanie, Ifremer Brest – Plouzané, France ([email protected])  ESPERT Sophie, DIPC, Univ. Politècnica de València – San Sebastian, Spain ([email protected]‐bordeaux.fr)  ESTUBLIER Audrey , IFPEN – Paris, France ([email protected])  FANDINO‐TORRES Olivia, Ifremer Brest – Plouzané, France ([email protected])  GARZIGLIA Sébastien, Ifremer Brest – Plouzané, France (sebastien.garziglial@ifremer)  GELI Louis, Ifremer Brest – Plouzané, France ([email protected])  GLENAT Philippe, Total E&P CSTJF – Pau, France France ([email protected])  GUIMPIER Charlène, ISM, UMR 5255 CNRS, Univ. de Bordeaux – Talence, France ([email protected])  LE MELINAIRE Pascal,……., (pln@b‐gh.com)  LE MENN Erwan, CNRS, Univ. de Nantes, France (erwan.lemenn@univ‐nantes.fr)  LE Quang‐Du, Univ. de Lille – Lille, France (quang‐[email protected])

13 Journées Hydrates, Brest, 09‐13 septembre 2019

 LE Thi‐Xiu, École Nationale des Ponts et Chaussées – Marne‐la‐Vallée, France (thi‐ [email protected])  LEGOIX, Ludovic, ISM, Univ. de Bordeaux & Univ. de Lille – Talence, France (ludovic.legoix@univ‐lille.fr)  LEMAIRE Marine, École des Ponts ParisTech – Marne‐la‐Vallée, France ([email protected])  LEMAIRE Morgane, ISM, Univ. de Bordeaux & Univ. de Lille – Talence, France (morgane.lemaire@univ‐lille.fr)  LE MELINAIRE Pascal,……., (pln@b‐gh.com)  LE MENN Erwan, CNRS, Univ. de Nantes, France (erwan.lemenn@univ‐nantes.fr)  LESAGE Elodie, Université Paris Sud – Orsay, France (frederic.schmidt@u‐psud.fr)  LU Hailong, , Université de Peking, – Pekin, Chine ([email protected])  MARTIN‐GONDRE Ludovic, Institut UTINAM / Groupe Space – Besançon France (ludovic.martin@univ‐fcompte.fr)  MÉTAIS Cyrielle, ISM – Talence, France (cyrielle.metais@u‐bordeaux.fr)  ONDREAS Hélène, Ifremer Brest – Plouzané, France ([email protected])  PATT Antoine, Laboratoire Interdisciplinaire Carnot de Bourgogne, Univ. Bourgogne Franche‐Comté – Dijon, France (antoine.patt@u‐bourgogne.fr)  PICAUD Sylvain, Institut UTINAM, Univ. Franche Comte – Besançon, France (sylvain.picaud@univ‐fcomte.fr)  PONS Michel, LIMSI, CNRS – Orsay, France ([email protected])  RIBOULOT Vincent, Ifremer Brest – Plouzané, France ([email protected])  RINNERT Emmanuel, Ifremer Brest – Plouzané, France ([email protected])  RODRIGUEZ MACHINE Carla Thais, Univ. de Lille, France (carla‐thais.rodriguez‐ machine@univ‐lille.fr)  ROUXEL Olivier, Ifremer Brest – Plouzané, France ([email protected])  RUFFINE Livio, Ifremer Brest – Plouzané, France ([email protected])  SCALABRIN Carla, Ifremer Brest – Plouzané, France ([email protected])  SCHMIDT Frédéric, Université Paris Sud – Orsay, France – (frederic.schmidt@u‐psud.fr)  SILVESTRE‐ALBERO Joaquim, DIC, Univ. Alicante, Espagne ([email protected])  SIMON Jean‐Marc, ICB, Univ. de Bourgogne – Dijon, France (jmsimon@u‐bourgogne.fr)  SINQUIN Anne, IFPEN – Paris, France ([email protected])  TALEB Farah, Ifremer Brest – Plouzané, France (farah‐[email protected])  TANG Anh Minh, École des Ponts ParisTech – Marne‐la‐Vallée, France (anh‐ [email protected])  THEOCHARIS Alexandros, École Nationale des Ponts et Chaussées – Marne‐la‐Vallée, France ([email protected])  TOBIE Gabriel, Univ. de Nantes, France (Gabriel.Tobie@univ‐nantes.fr)  TOFFIN Laurent, Ifremer Brest – Plouzané, France ([email protected])  TRINQUIER Anne, Ifremer Brest – Plouzané, France ([email protected])  VENET Saphir, Université de Pau, France (saphir.venet@univ‐pau.fr)

14 Journées Hydrates, Brest, 09‐13 septembre 2019

LIST OF ABSTRACTS

15 Journées Hydrates, Brest, 09‐13 septembre 2019

16 Journées Hydrates, Brest, 09‐13 septembre 2019

Gas‐hydrate Pockmarks in deep water Nigeria: formation, evolution and related hazards

Nabil Sultan*

*Ifremer, REM/GM/LAD, centre de Bretagne – [email protected]

The PREOWEI field is located in the Gulf of Guinea on the west coast of central Africa, south of Nigeria and seaward of the modern Niger Delta. The PREOWEI field is characterized by the presence of numerous circular to sub‐circular features of different shapes and sizes ranging from a small ring depression surrounding an irregular floor to more typical pockmarks with uniform depression. Acquired geophysical, geotechnical and sedimentological data show the presence of a common internal architecture of the pockmark structures with inner sediments rich in free gas and gas hydrates at shallow depths below the seafloor. The aim of this talk is to summarize key findings undertaken during the last decade based on different scientific ocean expeditions (NERIS 1&2, ERIG3D and Guineco‐MeBo). One of the main finding concerns the importance of the hydrate dissolution and the evolution of the hydrate‐pockmarks in the PREOWEI field (Figure 1). Moreover and due to the temperature and pressure conditions of the PREOWEI site and the evidence of gas infiltration to the shallow subsurface, free gas and gas hydrates are considered as a major hazard source. Recent activities based on advanced numerical analyses have revealed the importance of such hazard analysis for engineering subsea structure developments.

Figure 1. Sketch (a to f) of different steps in pockmark evolution during hydrate formation and dissolution.

17 Journées Hydrates, Brest, 09‐13 septembre 2019

Guest Trapping and Selectivity within mixed Clathrate Hydrates: a Grand Canonical Monte Carlo Study coupled with thermodynamic modelling

A. Patt1,2, J. M. Simon1, S. Picaud2, J. M. Salazar1

1 Laboratoire Interdisciplinaire Carnot de Bourgogne UMR 6303, 9 Av. Alain Savary, F‐ 21078 Dijon, France 2 Institut UTINAM UMR 6213, 41 bis Av. de l’Observatoire, 25010 Besançon, France

Naturally occurring clathrate hydrates are at the heart of important environmental concerns and are also subjects and/or means of study for astrophysicists (O. Mousis et al.; Faraday Discuss. 147 (2010) 509). In situ conditions generally imply the presence of gas mixtures in the hydrate forming system. The question of the competition between the different molecular species in the process of clathration is then raised. Namely, the selectivity is of interest to determine the most stable hydrates formed for given compositions of gas mixtures. Among the clathrate hydrates of interest for extraterrestrial environments are the N2, CO, and mixed N2‐CO hydrates (O. Mousis et al.; Astrophys. J. 691 (2009) 1780). They are involved in the models of the formation of planetesimals and planetary atmospheres. A better understanding of the trapping capabilities of those hydrates can help providing constraints on the chemical abundances of astrophysical environments.

To that end, Grand Canonical Monte Carlo (GCMC) simulations constitute a useful and effective tool to study those properties. In continuity with the adsorption analogy used to model the equilibria of clathrate hydrates in the van der Waals – Platteeuw theory, GCMC simulations can give the quantity of trapped, or adsorbed‐like, molecules in a clathrate hydrate as a function of the chemical potential or applied pressure.

In the case of the mixed hydrate, we report a significant selectivity towards CO, in agreement with experimental work (C. Pétuya, Ph.D. thesis, 2017), especially at low temperatures. A two‐site adsorption behavior is evidenced for structure II hydrates considered in this work: the small cages being more likely filled than the large ones. Additionally, we show that the Ideal Adsorbed Solution Theory (IAST) gives results which are in excellent agreement with those of our binary GCMC simulations (A. Patt et al.; J. Phys. Chem. C 122 (2018) 18432). The influence of the gas phase composition on the molecular selectivity is highlighted from both GCMC and IAST calculations, for which we obtained qualitative agreements with experiments. After focusing on N2 and CO hydrates, the study has been extended to other hydrates such as CO2, CH4, C2H6, and the corresponding mixtures.

18 Journées Hydrates, Brest, 09‐13 septembre 2019

How different formation pathways impact the structure and separation efficiency in CO2‐N2 gas mixtures using TBAB Semi‐clathrate Hydrates

C.T. Rodriguez1, Q‐D. Le1, C. Focsa1, C. Pirim1, B. Chazallon1

1 Univ. Lille, CNRS, UMR 8523 – PhLAM ‐ Physique des Lasers Atomes et Molécules, CERLA – Centre d’Etudes et de Recherche Lasers et Applications, F‐59000, Lille, France

Since several years a great effort has been devoted to reduce carbon dioxide (CO2) emissions from anthropogenic activities (e.g. thermal power plants and steel making industries). However, the also increasing energy demand worldwide makes the utilization of natural gases and fossil fuel resources still essential for the process. These emissions are composed mainly of CO2+N2 gas mixtures (with a CO2 concentration varying between 5 and 40%) (D’alessandro, D. M.; Smit, B.; Long. J. R.; Angew. Chem. Int. (2010) 6058‐6082), causing a negative impact in the composition of the atmosphere with the dramatic increase of greenhouse gas concentrations. One way to overcome this problem at the short to mid‐term is to apply CO2 Capture and Storage technology (CCS), for which continuous research efforts are being deployed for the optimization of the process. In this context, the Hydrate‐Based Separation Process (HSBP) represents a promising alternative to the existing technologies, for which a number of drawbacks have been pointed out from the energetic and environmental point of view. Specifically, in the hydrate technology, thermodynamic promoters can be added to water in order to mitigate the operative conditions suitable for an optimized process. Ionic salts (tetra‐n‐butyl ammonium bromide (TBAB)) dissolved in water induce hydrates formation at specific p, T conditions and can remove CO2 from a gas stream by guest‐gas encapsulation (Hashimoto, H.; Yamaguchi, T.; Ozeki, H.; Muromachi, S.; Sci. Rep. (2017) 1‐10). Literature on TBAB semi‐clathrates has mostly focused on the study of low concentrations of salt samples while studies for high concentrations (e.g. 35%) are lacking. In order to diminish this major gap in the literature, this research examines the CO2 capture in a sample formed from (10%CO2+90%N2)‐35%TBAB‐H2O at a pressure of 3.7MPa in a high‐pressure optical reactor with two distinct temperature protocols typically used in hydrate processes. The objective is to investigate the influence of the formation protocol on the structure and separation efficiency of the gas mixture at several temperatures on approaching the dissociation temperature. Protocol 1 represents a multi‐cycling fast cooling whereas protocol 2 represents a step‐by‐step slow cooling. The samples are analyzed by micro‐Raman spectroscopy and optical macroscopy. A new experimental dissociation temperature is found for our gas mixture at T=287.8K ± 0.3K. In terms of structure, the encapsulation of the guest‐gases leads to a structural transition as previously observed (Chazallon, B.; Ziskind, M.; Carpentier, Y.; Focsa, C.; J. Phys. Chem. 118 (2014) 13440‐13452). Raman analysis reveals the influence of the structure on the selectivity by the measure of the separation factor (S.F). Structure type A is shown to perform better for the separation than structure type B or the polymorphic phase. Further, Protocol 2 shows a better performance than protocol 1. Finally, S.F changes while approaching dissociation along with an evolution of structure for the hydrate.

Ackowledgement: the authors thank the Région Hauts‐de‐France, the Ministère de

19 Journées Hydrates, Brest, 09‐13 septembre 2019 l’Enseignement Supérieur et de la Recherche and the European Fund for Regional Economic Development for their financial support (CPER CLIMIBIO).

20 Journées Hydrates, Brest, 09‐13 septembre 2019

Structural stability of CO clathrate hydrates using DFT calculations

Claire Petuya1,2, Ludovic Martin‐Gondre3, Cyrielle Métais1,3,4 and Arnaud Desmedt1

1 Institut des Sciences Moléculaires (ISM) – Univ. Bordeaux, Talence, France 2 NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA 3 Institut UTINAM – Univ. Bourgogne Franche‐Compté, Besançon, France 4 Institut Laure Langevin (ILL), Grenoble, France

Contact : ludovic.martin@univ‐fcompte.fr

Carbon monoxide (CO) hydrate might be considered an important component of the carbon cycle in the solar system since CO gas is one of the peredominant forms of carbon. Intriguing fundamental properties have also been reported: the CO hydrate initially forms in the sl structure (kinetically favored) and transforms into the sll structure (thermodynamically stable) (Zhu, J., Du, S., Yu, X., Zhang, J., Xu, H., Vogel, S.C., Germann, T.C., Francisco, J.S., Izumi, F., Momma, K., Kawamura, Y., Jin? C. and Zhao, Y., Nat. Commun. 5, (2014) 4128). Understanding and predicting the gas hydrate structural stability then become essential. The aim of this work is thereby, to study the structural and energetic properties of the CO hydrate using density functional theory (DFT) calculations. Performed on a complete unit cell (sl and sll), DFT derived energy calculations lead indeed to the sll structure most thermodynamically stable. In addition, increasing the CO content in the large cages has a stabilizing effect on the sll structure, while it destabilizes the sl structure in agreement with recent experimental results as shown in Fig. 1 (Petuya, C., Martin‐Gondre, L., Aurel, P., Damay, F. and Desmedt, A., J. Chem; Phys. 150 2019) 184705).

Figure 1: Calculated binding energy as a function of the large cage occupancy

21 Journées Hydrates, Brest, 09‐13 septembre 2019

Thermodynamic study of the phase equilibria in the gas‐water‐ (NaCl) systems using electrolyte CPA EoS

S. Chabab1, A. Valtz1, A. Chapoy1, 2, C. Coquelet1

1 Mines ParisTech, PSL University, Centre of Thermodynamics of Processes, 35 rue Saint Honoré, 77305 Fontainebleau Cedex, France 2 Institute of Petroleum Engineering, Heriot‐Watt University, Hydrates, Flow Assurance & Phase Equilibria Research Group, Edinburgh EH14 4AS, Scotland,UK

Carbon dioxide emissions, which is the main greenhouse gas (in terms of quantity) produced by human activity, are constantly increasing, mainly due to the exploitation and use of fossil fuels. One of the possible solutions, that is of great interest to industrial actors in the gas sector, is to capture, transport and store carbon dioxide in deep geological formations (salt caverns, saline aquifers, etc.). In these underground geological environments, the gas (CO2) is in contact with saline water, and depending on pressure and temperature conditions, CO2 hydrates can be formed (especially in the case of CO2 storage as hydrate in deep oceans). The flue gases from oxy‐fuel combustion are mainly composed of CO2, O2 and steam. As part of the ANR FLUIDSTORY project, one possibility is to store these CO2‐rich emissions in salt caverns and use them later for methanation. During the transport or extraction of the CO2+O2 mixture from the cavities, the rapid pressure drops can lead to condensation of water and then the formation of hydrates, which in turns can leads to the clogging of pipelines.

The knowledge of phase equilibria as well as the hydrate stability zone of the CO2‐ O2‐ H2O and CO2‐H2O‐salt systems is of great importance. To achieve this, it is essential to develop a thermodynamic model that is sufficiently accurate under the operating conditions of transport and storage. This requires the availability of reliable experimental data for this type of system. In this work, measurements of gas hydrate dissociation for CO2 in the presence of NaCl and for the CO2/O2 mixture were carried out with an experimental setup based on the isochoric method.

Fig. 1 : The e‐PR‐CPA model in terms of Helmholtz energy.

A new electrolyte thermodynamic model (e‐PR‐CPA), which takes into account all molecular and electrolyte interactions (Fig. 1), has been developed. This model has been successfully applied to predict the solubility of CO2 and other gases (CH4, O2, H2, etc.) in brine solution as well as the water content in a wide range of pressure, temperature and salinity. The van der Waals and Platteeuw (vdWP) theory was combined with the e‐PR‐ CPA model to predict the hydrate forming conditions in the presence of electrolytes. The developed model (e‐PR‐CPA + vdWP) captures very well the effect of electrolytes (NaCl) on the CH4 (for validation) and CO2 hydrate stability zone. The model predictions are in good agreement with the experimental measured and literature data.

22 Journées Hydrates, Brest, 09‐13 septembre 2019

Contactless measurement of the mechanical properties of methane hydrate at pore scales

D. Atig1, D. Broseta, J‐M. Pereira2, R. Brown3

1CNRS/ TOTAL/ UNIV PAU & PAYS ADOUR E2S UPPA, Laboratoire des fluides complexes et de leurs reservoirs, UMR5150, 64000 Pau, France.

2Laboratoire Navier, UMR 8205, Ecole des Ponts Paris‐Tech, IFSTTAR, CNRS, UPE, Champs‐ sur‐Marne, France.

3CNRS/ TOTAL/ UNIV PAU & PAYS ADOUR E2S UPPA, Institut des sciences analytiques et de physico‐chimie pour l’environnement et les materiaux, UMR5254, 64000 Pau, France.

Gas hydrates are ubiquitous on earth, notably at the edge of the continental margins and on the seafloor, where they contribute to the stability of marine sediments by their cohesion and their adhesion to mineral surfaces. Nowadays there is a great motivation to study the mechanical behavior of gas hydrates, due to their interests in many energy and environmental applications. So far, the behavior of gas hydrate bearing sediments depends largely on the distribution of gas hydrate within the pore space. However, the behavior of gas hydrate is little or not studied at pore scale. In the literature, three common “pore habits” are distinguished, considering the existence only of water and hydrate, but not free gas: pore filing, load bearing and cementing. Recently, studies confirmed the presence and the abundance of a new pore habit, referred to as “mineral coating”: a few micron‐thin polycrystalline hydrate shell, not directly covering the sediment particles, but riding on an equally thin layer of intervening water, sandwiched between the substrate and the gas. In this study, using optical microscopy, the formation and growth of these shells are investigated across a water/methane meniscus in glass‐micron capillaries used as model pores, at 15 MPa of methane pressure. Then by developing a new contactless tensile test in combination with image processing, mechanical properties of these hydrate shells are determined. At low enough temperature, the hydrate first grows as a crust over the meniscus and continues advancing slowly on the gas side as a ‘halo’ riding over a water film on the glass. The halo comes to rest and adheres to the glass after an annealing period, effectively completing a hydrate shell (the crust and the halo) that isolates the water from the gas. During annealing at constant temperature, image processing shows homogeneous crystal growth of the hydrate shell. Tensile tests are carried out by generating thermally induced depression in the water compartment at constant methane pressure. Methane hydrate presents an elastoplastic behavior before brittle fracture. Tensile strength and elastic modulus are estimated as a function of annealing time (from 4 to 7 hours) and annealing supercooling (40.3 to 21.8°C). Both are higher at low temperatures, whereas annealing time seems not to affect the elastic modulus, but the hydrate is more resistant at short annealing time. Our data contribute to fitting the 5 orders of magnitude gap between molecular simulations and current experiment at mm to cm scale.

23 Journées Hydrates, Brest, 09‐13 septembre 2019

Cascades of hydrate filaments promoted by a porous substrate, activated charcoal

S. Venet1, R. Brown2, D. Broseta1

1 Laboratoire des fluids complexes et de leurs reservoirs (LFCR), UMR CNRS 5150, Université de Pau et des Pays de l’Adour, Av. de l’Université, B.P. 1155, 64013 Pau Cedex, France 2 Institut des sciences analytiques et de physico‐chimie pour l’environnement et les matériaux (IPREM), UMR CNRS 5254, Université de Pau et des Pays de l’Adour, Hélioparc, 2 AV. P. Angot; 64053 Pau Cedex, France

An unusual gas hydrate morphology, referred to here as “hydrate filaments” or “hydrate fibres”, is observed in the presence of activated charcoal beads (diam. ca. 400 µm) under the right conditions of pressure and temperature and bead saturation. This morphology ensures rapid and uninterrupted hydrate growth, unlike the usual, self‐ frustrating growth of conventional polycrystalline hydrate films at water/guest interfaces. We use transmission optical microscopy to investigate the growth mechanisms, using cyclopentane (CP) as the hydrate‐former, because, although its formation requires prior freezing of water into ice, the hydrate is stable at ambient pressure below a temperature of 7 °C In order to understand the phenomena involved in this novel growth process, which has potential applications for water treatment and desalination, we use a single charcoal bead placed in a square borosilicate capillary used as an optical cell. The temperature is well controlled over a wide range, from ‐30 °C to room temperature. The capillary is initially filled with liquid water and CP, and the bead is most often positioned initially at the interface (meniscus) between these two phases, either by introducing from the CP side or from the water side. Growth of filaments is most effective when the bead is pre‐saturated with CP. Filaments radiate widely from the bead (several times the bead diameter). In some experiments, the guided flow of bubbles indicates the filaments are hollow. Possible mechanisms for continuous hydrate growth will be discussed, particularly the problem how growth of continuous hydrate filaments out of the porous substrate, sidesteps a self‐extinguishing crust, e.g. is the process similar to hydrate halos reported by Touil et al.1?

[1] Touil, A.; Broseta, D.; Hobeika, N.; Figure 2: Growth of hydrates in the form of filaments grown from an activated charcoal bead observed under Brown. R.; Langmuir 33 (2017) 41. optical microscopy (scale bar 500µm). The bead, initially loaded with CP, lies in water near a CP/water inteface, now covered with a polycristalline, self- inhibiting crust of hydrate. 24 Journées Hydrates, Brest, 09‐13 septembre 2019

Grain‐scale morphology and distribution of methane hydrates formed in sand sediment under excess gas conditions

1 1 2 1 2 1 3 1 T.X. Le , M. Bornert , R. Brown , P. Aimedieu , D. Broseta , B. Chabot , A. King , A.M. Tang

1 Laboratoire Navier (UMR8205 IFSTTAR‐ENPC‐CNRS), Université Paris Est, Marne‐la‐vallée, France 2 L'Université de Pau et des Pays de l'Adour, France ; 3 Synchrotron SOLEIL, France

Physical/Mechanical properties of sediments containing methane hydrates (MH) depend considerably on hydrate morphologies and distribution within the porous space. Studies on MH morphologies and pore distribution in sediments are thus of importance for interpretations of geophysical data and reservoir‐scale simulation in the scope of methane gas production. X‐ray computed tomography (XRCT), synchrotron radiation X‐Ray computed tomography (SXRCT) and optical microscopy have been used to investigate pore‐scale morphologies and pore distribution of hydrates in sediments. However, it is really challenging due to not only the need of special experimental setups (high pressure and low temperature should be maintained) but also poor XRCT image contrast between methane hydrate and water. In this study, MH growth and morphologies in sandy sediments under excess gas conditions were investigated by using SXRCT combined with Optical Microscopy. Both pure and saline waters were used. Mechanisms of MH nucleation/growth are brought to light thanks to high temporal resolution of SXRCT and Optical Microscopy. Furthermore, observed MH morphologies and pore repartition compared to existing models (cements, load bearing and pore‐filling) are discussed. Water moves from menisci to form MH around nearby sand surfaces. MH morphologies in sample are not only heterogeneous at the pore scale but also at the sample scale due to water migration. Different types of MH morphologies (example shown in Figure 1) could exist in the sample.

Figure 3. Images showing different morphologies of MH: (a) crystals; (b) layer (Image dimensions: 0.63 mm x 0.63 mm)

25 Journées Hydrates, Brest, 09‐13 septembre 2019

Insights into the characterization of gas hydrate‐bearing sediments from in situ geotechnical and acoustic measurements

Garziglia, S., Taleb, F., Sultan, N

Characterizing the structure and mechanical behaviour of sediments containing gas hydrates is critical in assessing the potential for slope instabilities as a result either of hydrocarbon exploitation activities or environmental changes. Concerns over the metastable nature of gas hydrates have led to a series of investigations aiming at capturing trends in geotechnical properties as a function of the hydrate content together with the characteristics of the host matrix under varying stress and thermal conditions. Most efforts in this direction have relied on the use of synthetic samples under laboratory‐controlled conditions. Some of the trends that emerged have been confirmed through the analysis of natural samples collected with pressure corers. The cost of such sampling systems along with the difficulties to preserve hydrate in their stability conditions has sustained interest in in situ testing methods. Piezocone sounding is one of the method that has long been considered as particularly well‐ suited as it can provide, at the same time, continuous profiles of three independent measurements. With the resolution of 2 cm, such profiles are efficient means of picturing the structure of the subsurface and quantifying the associated changes in mechanical properties. To complete the characterization of the medium at a similar fine scale, hydrate contents can be derived from acoustic soundings. Other methods such as dissipation tests can be carried out with piezometer instruments to determine the permeability properties of the medium. The aim of this presentation is to synthesize the insight gained by using these different in situ methods in two distinct areas located offshore Nigeria and in the Black Sea. Those insights first relate to the characterization of the influence of the quantity and morphology of hydrates on the properties of their host fine‐grained sediments. They also proved useful in understanding the processes controlling the large scale distribution of hydrates in sediments in high gas flux systems.

26 Journées Hydrates, Brest, 09‐13 septembre 2019

Mechanical homogenization of gas hydrate bearing soils

A. Alavoine1, P. Dangla1, J.‐M. Pereira1

1 Université Paris‐Est, Laboratoire Navier, UMR 8205 (ENPC‐IFSTTAR‐CNRS), Marne‐la‐Vallée, France

The research regarding the geomechanics of natural gas hydrate reservoirs in oceanic sediments of permafrost regions has increased these last two decades. The growing interest in the potential energy resource that such deposits represent has raised environmental concerns. Indeed, the dissociation of gas hydrates in soil layers of the seafloor can lead to instabilities and landslides for example (Kayen, R.; Lee, H.; Marine Geotechnology 10 (1991) 125‐141). The complexity of the microstructure of soils containing gas hydrates makes it difficult to model through simple macroscopic mechanical laws. One must take into account characteristics like hydrate volume fraction, morphology and location in porous media. Numerical homogenisation techniques allow us to study the apparent behaviour of heterogeneous microstructures. We use a Fast Fourier Transform based (FFT) method (Gélébart, L.;Mondon‐Cancel, R.; Comput. Mater. Sci. 77 (2013) 430‐439) to homogenise the mechanical response of different types of microstructures. Nonlinear mechanical laws like elastoplasticity can be used for the phases composing the material. Real microstructures can be homogenised since the technique is based on a space discretisation into pixels. Furthermore, this numerical solution can be used in multi‐scale approaches or to develop constitutive laws

27 Journées Hydrates, Brest, 09‐13 septembre 2019

GARAH: a GeoERA project addressing knowledge gaps to allow gas hydrate assessment of the European continental margin A. Burnol1, I. Thinon1, H. Aochi1, S. Stephant1, Ricardo León2

1 BRGM, 3 avenue Claude Guillemin, 45060, Orléans, France 2 Geological survey of Spain (IGME), Rios Rosas 23, 28003 Madrid, Spain

The main variables controlling the gas hydrate stability zone (GHSZ) are: gas‐composition; geothermal gradient; pressure (bathymetry); and seafloor temperature. The lack of a complete available dataset (geological and oceanographic data) in the European continental margin zone limits our knowledge about key factors controlling the base of GHSZ.

The GeoERA GARAH project (2018‐2021) aims to address gaps in knowledge, and build the pan‐European gas‐hydrate data infra‐structure necessary to allow assessment of the European continental margin. This includes objectives to: 1) Develop a harmonized database of European gas‐hydrate data; 2) Identify specific areas of interest or having critical knowledge gaps which would benefit from further research; 3) Provide recommendations on how future data should be collected and stored to be fully interoperable. These objectives will provide critical information for assessments relating to geohazards and risks, assessments of the abundance of sediment‐hosted gas‐hydrates, and evaluations of the role that CO2‐rich hydrates might play for a geological storage of CO2 in deep‐sea sediments (deep offshore option).

In some areas like the Bay of Biscay and west Galician margins, there is a low density of data. This year, BRGM contribution was to upload new data concerning this area: thickness of post‐rift sedimentary layer; Major faults from a bibliographic synthesis; the location of the theoretical base of the GHSZ supposing a mixed CO2 hydrate with 3.6 mol% N2 in CO2 (Burnol, A; Gas Hydrates 2: Geoscience Issues and Potential Industrial Applications, John Wiley & Sons, Inc.(2008) 267‐284).

In the next steps of the project, a multi‐risk approach will be taken using this database to study the potential link between destabilization of gas hydrate and other geohazards like natural seismicity. GARAH project will thus play a crucial role in advancing our knowledge about, and modelling of, gas‐hydrate stability along European margins.

Acknowledgment GARAH project. GeoERA ‐ GeoE.171.002

28 Journées Hydrates, Brest, 09‐13 septembre 2019

Influence of alkaline feldspars‐surrogates on the formation kinetic and the

selectivity of CO2‐N2 mixed hydrates under astrophysical and geophysical conditions

Morgane LEMAIRE1,2, Marc DUSSAUZE2, Claire PETUYA3, Vivian NASSIF4, Claire PIRIM1, Bertrand CHAZALLON1, Arnaud DESMEDT2

1Univ. Lille, CNRS, UMR 8523 ‐ PhLAM‐ Physique des Lasers Atomes et Molécules, F‐59000 Lille, France 2Univ. Bordeaux, CNRS UMR 5255 ISM‐ Institut des Sciences Moléculaires, 33405 Talence, France 3JPL NASA PASADENA, 4800 Oak Grove Dr, 91109, Pasadena, U.S 4Institut Laue Langevin / Institut NEEL CNRS/UGA UPR2940, 38042 Grenoble, France

Clathrate hydrates can be found in a variety of natural environments: marine hydrate‐ bearing sediments, polar ice cores, atmospheric aerosols1,2. Furthermore, they possess a large potential for useful technical and industrial applications in energy and environmental fields, such as the prevention of hydrate plugging in oil and gas pipelines, the exploitation of natural gas hydrates in deep ocean’s sediments or permafrost regions, the storage and 3,4,5,6 transportation of natural gas in solid hydrate form, and CO2 capture and storage . In this work, special interest is given to the natural sediment influence on the CO2/N2 mixed hydrate. Aluminosilicates (sodium, calcium and potassium feldspar) are minerals that could be found on Earth as well as on planets7, moons8 or meteorites8 with Si‐Al substitution and charged with alkaline. This replacement allows them to have both larger reaction and hydrophobic 2 surface, promoting CO2‐hydrate dissociation. Our recent study, using the high‐resolution neutron two‐axis powder diffractometer (D1B‐ILL) showed that alkaline surrogates act like inhibitor of the gas hydrate kinetics of formation. Indeed, the alkaline‐silicate surrogate could interact with the carbon dioxide and the ice to form carbonates, preventing the hydrate formation. In order to subsequently investigate their influence on gas hydrate properties, the selectivity analysis has been carried out on the 50%CO2‐N2 mixed gas hydrate by means of confocal Raman microspectrometry. It is shown that the presence of alkaline ions influenced this parameter by decreasing CO2 selectivity. Thus, the chemical composition of the surrogates, in particular the alkaline, plays a key role in the gas hydrates formation. The second objective of this work was to understand the influence of these surrogates on the gas hydrates formation under astrophysical conditions – not well known to the best of our knowledge. Indeed, most experimental investigations of gas hydrates are performed by using gas hydrates formed under high pressure and high temperature (with respect to astrophysical conditions.9,10 In this work, water‐gas deposition experiments have been performed at astrophysical conditions (i.e. low temperatures and mbar pressure) to form N2‐ hydrate and CO2‐hydrate. In‐situ micro‐Raman spectroscopy, appropriated technique to investigate gas hydrate11, are used to explore various conditions of formation. It is revealed that the suitable condition for the hydrate formation appears to be a multi‐layered process.

29 Journées Hydrates, Brest, 09‐13 septembre 2019

Such a result is particularly relevant with respect to the dwarfs planets and some moons, that might enable the formation of a multi‐layered ice in contact with gases.12,13

Acknowledgements: This work is supported by ANR‐15‐CE29‐0016 MI2C. The Institut Laue Langevin is thanked for provision of beam times. Jennifer Noble (PhLAM – Univ. Lille) is thanked for fruitful and helpful discussions. (1) Moridis G. J. et al, SPE Reservoir Eval. Eng. 2009, 12 (5), 745−771. (2) Broseta D., et al., Wiley‐ISTE:London, 2017 (3) Seo Y. et al, J. Chem. Eng. Data 2008, 53, 2833–2837. (4) Kvamme,B. et al, J. Nat. Gas Sci. Eng. 2015. (5) Linga P. et al, Environ. Sci. Technol. 2008, 42, 315–320. (6) Eslamimanesh A. et al, Chem. Eng. Sci. 2012, 81, 319–328. (7) Deer W.A. et al, Geological Society¸2004, London. (8) Castillo‐ Rogez J. et al., Meteorit. Planet. Sci.¸2018, 9, 1820‐1843. (9) Hallbrucker A., J. Chem. Soc. Faraday Trans., 1994, 90(2), 293‐295.//(10) Lunine J.L., Stevenson D.J., Astrophys. J., 1985, 58, 493‐531 (11) Chazallon B., et al., In : Broseta D., et al., Wiley‐ISTE:London, 2017 (12) Mitri G., Showman A.P., Icarus, 2008, 193(2), 387‐396.//(13) Travis B.J., Schubert G., Icarus, 2015, 250, 32‐42.

30 Journées Hydrates, Brest, 09‐13 septembre 2019

Clathrate hydrate on planet Mars: at present time and in the past

F. Schmidt1, G. Cruz‐Mermy1, E. Lesage1

1 GEOPS, Université Paris‐Sud, CNRS, France

Clathrate hydrate has been proposed to be present in various geological context in the Martian history. We propose here to review the condition and the implication of such phase.

At present time: methane has been detected by various techniques in the atmosphere of Mars, but observations are really puzzling because they suggest a very short (few weeks) lifetime, in comparison with the known chemistry expectation (tens of years). Methane has been proposed to as a phase to trap CH4 but also to release it rapidly. Abnormal preservation of methane clathrate has been proposed to solve this open question. Also, clathrate may be present in the polar cap of Mars because of the co‐existence of both water and CO2 ices.

In the past: Most volcanic sulfur released to the early Mars atmosphere could have been trapped in the upper cryosphere under the form of CO2‐SO2 clathrates. Huge amounts of sulfur, up to the equivalent of a ~1 bar atmosphere of SO2, would have been stored in the Noachian (~4Gy) upper cryosphere, then massively released to the atmosphere during the Hesperian (~3.5 Gy) due to rapidly decreasing CO2 atmospheric pressure. It could have resulted in the formation of the large sulfate deposits observed mainly in Hesperian terrains, whereas no or little sulfates are found at the Noachian. We point out the fact that CO2‐SO2 clathrates formed through a progressive enrichment of a preexisting reservoir of CO2 clathrates and discuss processes potentially involved in the slow formation of a SO2‐rich upper cryosphere. We show that episodes of sudden destabilization at the Hesperian may generate 1000 ppmv of SO2 in the atmosphere and contribute to maintaining the surface temperature above the water freezing point.

31 Journées Hydrates, Brest, 09‐13 septembre 2019

Clathrate hydrates in the icy worlds of the Solar system

G. Tobie1, E. Le Menn1, L. Bezacier1, Bollengier O.1, Choblet G.1, C. Fauguerolles1, O. Grasset1, Harel, L. 1, Le Mouélic S.1, Marais, H.1, Massé, M.1, Morizet Y.1, Nna Mvondo, D.1, Oancea, A.1, Robidel, R.1

1 Laboratoire de Planétologie et Géodynamique, UMR‐CNRS 6112, Université de Nantes, France

Beyond Mars, most of the solid bodies of the solar system contains water ice in large quantities, potentially up to 50% of their mass. Space exploration of the Outer solar system has revealed that several icy bodies harbor liquid water underneath their cold icy surface, where large quantities of gas compounds may be stored in the form of clathrate hydrate (Tobie et al. ApJ 752:125 (2012)) The most spectacular discovery of these two last decades was the observation by the Cassini spacecraft of water vapour and icy grains erupting from the south pole of Saturn’s moon Enceladus. After ten years of exploration of Saturn’s system by the Cassini‐Huygens mission, it was understood that this eruption was directly connected to a subsurface ocean, only a few kilometers beneath the surface (Choblet et al. Nature Astro. 1 (2017) 841‐947, Postberg et al. Nature 558 (2019) 564‐568). By flying through the watery plume, Cassini samples for the first time materials coming from an extraterrestrial water reservoir. Evidence of water vapor erupting from Europa’s surface has been also reported (e.g. Roth et al. Science 343 (2014) 171‐174), indicating that oceanic materials may be sampled on this moon also by a future exploration mission.

These different discoveries indicate that active chemical exchanges are still operating on some of these moons and that gas clathrate hydrate may play a crucial role. In this context, during these last ten years, the LPG developed a joint approach combining observation, experimentation and numerical modeling to understand the implications of gas clathrate hydrate for the long‐term evolution and present‐day activity of icy moons. This includes high‐pressure experiments (up to 5 GPa) to determine the phase diagram of clathrate hydrates (mostly CO2 (Bollengier et al. GCA 19 (2013) 322‐339) and CH4 (Bezacier et al. PEPI 229 (2014) 144‐152) in the interior conditions of large icy worlds, acquisition of reference IR spectra of gas clathrate hydrate at low pressure and low temperature conditions ((Oancea et al. Icarus 221(2012) 900‐910), Nna Mvondo et al. Icarus (in revision)) in order to anticipate their detection at the surface of icy moons, numerical modeling on the interior structure to determine the stability range of clathrate hydrate and their possible transport to the surface (Tobie et al. ApJ 752:125 (2012), Choblet et al. Icarus 285 (2017) 252‐262)). This presentation will provide an overview of the work that has been performed these last years by our group to address the role of clathrate hydrate on the thermo‐chemical evolution of icy moons.

32 Journées Hydrates, Brest, 09‐13 septembre 2019

Stability of mixed CH4‐CO2‐N2 hydrates and mass transfer during gas exchange

L.N. Legoix1,2,*, L. Ruffine2, C. Deusner1 and M. Haeckel1

1 GEOMAR, Helmholtz Centre for Ocean Research Kiel, Wischhofst. 1‐3, D‐24148 Kiel, Germany 2 IFREMER, Institut Français de Recherche pour l’Exploitation de la Mer, Géosciencers Marines, 29280 Plouzané, France *Actual affiliation : Université de Lille, PhLAM‐Physique des Lasers Atomes et Molécules, F‐ 59000 Lille, France

The CCS processes (i.e., Carbon Capture and Storage) are gaining interest to decrease the atmospheric emissions of CO2. Clathrate hydrates are components suggested to separate CO2 from flue gas (i.e., contains mainly N2 and CO2) produced by industries, with the help or not of a hydrate promoter (Kang, S.‐P. and Lee, H.; Environ. Sci. Technol. 34 (2000) 20). Concerning the sequestration, the deep‐sea sediments are considered to be a possible alternative to other geological methods to sequester CO2 in the hydrate form (Ohgaki, K. et al.; J. Chem. Eng. Jpn 26 (1993) 5). However, the presence of N2 with CO2 could enhance the process of carbon sequestration, that opens the possibility to sequester directly a flue gas without using a separation process (Park, D.‐Y. et al.; Proc. Natl. Aca. Sci 103 (2006) 34). In this work (Legoig, L.N.; Diss. CAU Kiel (2019)), several laboratories experiments were done to give insights on CO2 sequestration in nature as a hydrate deposit. The phase equilibria data of CO2‐CH4 hydrates with a liquid CO2 phase shows that it is possible to store CO2 at higher temperature when CH4 is present. Then, the mechanisms of CH4 replacement by CO2 were studied. Finally, a series of high‐pressure experiments to study the behavior of a fluid downstream a well for the sequestration of a flue gas were done. The shrinking core kinetics, based on the diffusion of guest molecules in hydrates, makes the gas exchange slow. However, CO2 is still preferentially retained compared to N2, and CH4 were produced during both gas injections and depressurizations steps.

33 Journées Hydrates, Brest, 09‐13 septembre 2019

High performance of gas hydrates confined in nanoporous solids for CH4 and CO2 storage

M. Martínez‐Escandell*, M.E. Casco, C. Cuadrado‐Collados, J. Silvestre‐Albero

1 Laboratorio de Materiales Avanzados, Universidad de Alicante, Alicante, Spain

*Presenting author’s e‐mail: [email protected]

Introduction The discovery of sediments deep under sea and in the permafrost containing methane molecules in the form of gas hydrate has opened a wide range of potential applications for energy storage. Gas hydrates are crystalline inclusion compounds that are formed when small guest molecules contact water in specific pressure and temperature conditions (below 10ºC, above 3.5 MPa).1 In the specific case of methane (the main component of natural gas), sI hydrates can store one molecule of methane for every six molecules of water, i.e. a maximum of 180 volumes (STP) per volume. Hence, artificial methane hydrates can be anticipated as a feasible alternative for storage and transportation of natural gas at much lower cost and safer than the current technologies, e.g. liquid natural gas and compressed natural gas. Despite the promising performance of gas hydrates, their nucleation and growth is an interfacial phenomena associated with very slow kinetics. However, recent studies from our research group have shown that activated carbons with a widely developed porous structure and a proper surface chemistry can promote the nucleate and growth of gas hydrates (methane) under milder conditions than nature (2ºC and 4‐6 MPa), with faster kinetics (within minutes) and with a stoichiometry that mimics natural hydrates.2 Interestingly, the performance of these confined hydrates highly depends not only in the textural properties of the host carbon structure (pore size and shape) but also in the surface chemistry. Last but not least, the nucleation and growth kinetics are highly sensible to the nature of the liquid media, e.g. to the presence of a saline environment.3

Materials and Methods

Activated carbon material has been prepared by chemical activation with anhydrous KOH of a mesophase pitch from a VR residue, using a KOH:precursor ratio 6:1 (w/w). The mesophase pitch and the KOH were initially mixed in a ball mill for 30 min, and subsequently the mixture was submitted to an activation treatment in a horizontal furnace at 1073 K for 2h, under a nitrogen flow of 100 mL/min. The final material was washed with 10% HCl solution and distilled water until neutral pH. For the adsorption experiments in wet conditions, the petroleum‐pitch activated carbon (PP‐ AC) was humidified under water‐supplying conditions denoted by Rw. Relative humidity conditions were modified to achieve sample under‐ and over‐saturated.

34 Journées Hydrates, Brest, 09‐13 septembre 2019

High‐pressure methane and CO2 adsorption measurements were performed in a homemade fully automated equipment designed and constructed by the LMA group. Adsorption measurements were performed up to 10 MPa at 2ºC.

Results and Discussion

High‐pressure methane and CO2 adsorption measurements clearly show that the pre‐ humidification of the carbon material with ultrapure water gives rise to a sudden increase in the amount of methane adsorbed, preferentially in volumetric basis. The increase storage capacity in wet carbons must be attributed to the formation of gas hydrates in the confined nanospace of the carbon material, as deduced from synchrotron X‐ray diffraction measurements.2 Furthermore, the presence of the carbon material as a host structure allows to improve the kinetics compared to the bulk hydrates. These confined hydrates can be used to store either CH4 or CO2, upon request. Interestingly, the scenario changes dramatically in the presence of seawater. Under these conditions the extent of hydrate formation decreases, preferentially at 2ºC (see Fig. 1). Furthermore, the presence of salt inhibits the nucleation process as reflected by a shift in the threshold pressure to higher values.

Te mp = 2º C 80

60

wt.) (% 40 CH4 n 20 H O/AC 2 Seawater/AC 0 0246810 P(MPa)

Figure 1. High‐pressure methane adsorption/desorption isotherms in sample PP‐ AC in pure and seawater environment.

Conclusions These results show that properly designed activated carbon materials can be used as a host structure to promote the formation of gas hydrates. These confined hydrates exhibit larger kinetics compared to their bulk counterparts. Furthermore, under confined environment CH4 can be easily replaced by CO2, thus opening the gate towards the application of natural methane hydrates as a long‐term CO2 reservoir. However, these processes are altered in the presence of salty water, preferentially at temperature around ice melting, with an inhibition of the gas hydrate.

Acknowledgment This work was supported by MINECO (Project MAT2016‐80285‐P) and GV (Project PROMETEOII/2014/004).

35 Journées Hydrates, Brest, 09‐13 septembre 2019

References

1. Sloan, E.D. (1998). “Clathrate of natural gases”, Marcel Dekker. New York. 2. Casco, M., Silvestre‐Albero, J., Ramirez‐Cuesta, A.J., Rey, F., Jordá, J.L. et al. (2015). Methane hydrates in confined nanospace can surpass nature, Nature Commun., 6, 6432 3. Cuadrado‐Collados, C., Fauth, F., Such‐Basañez, I., Martínez‐Escandell, M., Silvestre‐ Albero, J. (2017) Methane hydrate formation in the confined nanospace of activated carbons in seawater environment. Microp. Mesop. Mater.,255 220‐225

36 Journées Hydrates, Brest, 09‐13 septembre 2019

Investigation of the exchange kinetic between methane and carbon dioxide in gas hydrates: application to CO2 capture from flue gas analogs

Q.D. LE, C.T. RODRIGUEZ , C. PIRIM , B. CHAZALLON*

1 Univ. Lille, CNRS, UMR 8523 – PhLAM ‐ Physique des Lasers Atomes et Molécules, CERLA – Centre d’Etudes et de Recherche Lasers et Applications, F‐59000, Lille, France. Corresponding: bertrand.chazallon@univ‐lille.fr (B. Chazallon).

Abstract: Recovering methane (CH4) from natural gas hydrate deposits using carbon dioxide (CO2) injection is currently of interest, as it shows potential for producing an energy resource while mitigating CO2 emissions through CO2 sequestration in the meantime. Here, the kinetic of methane replacement by carbon dioxide in synthetic methane hydrates is evaluated by monitoring the change of pressure as a function of time during exchange processes. CO2 gas is captured within synthetic methane hydrates formed at different conditions of pressure and temperature. Both the exchange kinetic and the CO2 capture process are found to depend upon various factors, such as the driving forces applied for methane hydrates formation, the composition of the incoming CO2‐based gas stream, and the stirring speed during gas exchange. Effect of the driving force ∆P, which measures the pressure difference between the dissociation pressure and the formation pressure, has been tested between 6 MPa and 8 MPa for CH4 and 3.6 and 11.4 MPa for both pure CO2 and binary CO2‐N2 gas streams. At a temperature of 277K, the exchange kinetic with pure CO2 is greatly improved (by a factor ~60) when stirring is applied. Also, the kinetic is also improved by a factor ~5 when the exchange is performed on methane hydrates formed at higher pressure (8MPa), revealing how important the driving force applied to form methane hydrates is on the subsequent exchange kinetic. In contrast, the kinetic is reduced when exchange is carried out using a CO2‐N2 gas mixture.

Keywords: Kinetic; Thermodynamic; Gas hydrate; CH4‐CO2 replacement technology; driving force; Capture CO2

B. Chazallon, M. Ziskind, Y. Carpentier, and C. Focsa, “CO2 Capture using semi‐clathrates of quaternary ammonium salt: Structure change induced by CO2and N2 enclathration,” J. Phys. Chem. B, vol. 118, no. 47, pp. 13440–13452, Nov. 2014.

B. Chazallon and C. Pirim, “Selectivity and CO2 capture efficiency in CO2‐N2 clathrate hydrates investigated by in‐situ Raman spectroscopy,” Chem. Eng. J., vol. 342, pp. 171–183, Jun. 2018.

Acknowledgement: This work is supported by Interreg EU project Carbon2Value (2017‐ 2020)

37 Journées Hydrates, Brest, 09‐13 septembre 2019

Gestion de la vapeur dans les boucles de refroidissement secondaire à hydrates de gaz

M. Pons1, Z. Youssef1, A. Delahaye2, L. Fournaison2

1 LIMSI, CNRS, Université Paris‐Saclay, Bât 507 Rue du Belvédère, 91405 Orsay Cedex 2 Irstea, UR GPAN, 1 Rue Pierre‐Gilles de Gennes, 92761 Antony

Comparé aux coulis de glace (relativement connus), l’usage d’un coulis d’hydrate de gaz pour distribuer du froid se traduit par des phénomènes nouveaux. En effet, la décomposition des cristaux lors de la « fourniture de froid » génère du gaz (!) dont la densité est beaucoup plus faible que celle du coulis (re !), ce qui soulève deux questions. 1/ Ce gaz doit‐il continuer à circuler avec le coulis dans le réseau de distribution, dans lequel les utilisateurs sont habituellement desservis « en série » plutôt que « en parallèle » ? 2/ Quelles conséquences la présence du gaz a‐t‐elle sur le volume du réservoir de stockage de coulis, en termes de volumes et de pression ? Ces questions ont été étudiées à partir de données publiées [Compingt et al., 2009] sur un système de distribution de froid par coulis de glace (quantité de froid demandée, masse et volume de stockage), et ce pour deux types de coulis d’hydrates (de CO2 et mixte de CO2+TBPB), et pour deux configurations de stockage du gaz, soit sans soit avec compression. Les volumes nécessaires à l’ensemble du système de stockage (coulis + gaz) sont calculés en fonction des paramètres de fonctionnement du réseau et comparés au cas référence [Compingt et al., 2009].

Compingt, A., Blanc, P., Quidort, A.. 8th IIR Conf. Phase Change Materials and Slurries for Refrigeration and Air Conditioning. Kauffeld, M. (Ed.), Karlsruhe, Germany (2009), pp. 135‐ 144.

38 Journées Hydrates, Brest, 09‐13 septembre 2019

Flow loop experiments to study gas hydrate formation in gas‐water‐oil systems

V. ALMEIDA1, A. CAMEIRAO1, J‐M. HERRI1, P. GLENAT2

1 Centre SPIN, Ecole des Mines de Saint‐Etienne, 158 Cours Fauriel, 42023 Saint‐Etienne, France 2 TOTAL S.A.– CSTJF, Avenue Larribau, 64018 Pau Cedex, France

The formation of gas hydrates is a common problem in deep sea oil and gas pipelines, due to the low temperature and high pressure of these systems. Thermodynamic hydrate inhibitors (THIs) and kinetic hydrate inhibitors (KHIs) are the additives normally used by the industry to avoid hydrate formation. The THIs reduce the freezing temperature for hydrates formation. The disadvantages of THIs is that they require large volumes to be effective, they are costly and environmental unfriendly. The KHIs do not change the hydrate formation mechanisms and do not reduce the size of particles, but they delay the hydrates formation. KHIs are effective for a limited subcooling only. Alternatively, low dosage anti‐agglomerants (AAs) additives can be used. They are expected to reduce the particles size and prevent their agglomeration. Recent works reported in the literature have shown that some AAs reduce blockage for low water cuts systems, but they are not very effective for high water cuts scenarios. Consequently, investigations on high water cuts systems are still ongoing to understand the impact of several types of AAs, salt concentration and flow pattern on hydrates crystallization and transport. The focus of some recent research has been the use of salt to improve the effectiveness of AAs. The purpose of the present work is to study gas hydrate formation in pipelines by doing flowloop experiments. The Archimedes flowloop at Mines Saint‐Etienne (see [1] and [2]) is used for the tests, which are performed with Kerdane, water and gas. Recent improvements include the installation of acoustic emission probes to track hydrate formation, agglomeration and deposition. Preliminary experiments show that, with acoustic emission, chord length distributions and pressure drop measurements, it is possible to track the hydrate particles and identify deposition. Another improvement on the experimental apparatus was the installation of a permittivity probe, that helps identifying the continuous phase and the inversion of phase for some scenarios after crystallization. The first tests were at 30, 50, 80 and 100% water cuts, using methane. The objective of future experiments is to use natural gas and an AA additive with salt, focusing on high water cut systems. In addition, with the recent added acoustic emission and permittivity probes, we expect to be able to characterize the flow pattern before and after hydrate formation and classify the hydrate severity according to the observed flow patterns.

[1] Melchuna, A., Cameirao, A., Herri, J‐M., Glenat, P. Topological modeling of methane hydrate crystallization from low to high water cut emulsion systems. Fluid Phase Equilib., Vol. 413, pp. 158 – 169 (2016).

[2] Pham, T.K. Experimental study and modelling on methane hydrates crystallization under flow from a water‐oil dispersion at high water cut. PhD Thesis, 334 p., Mines Saint Etienne, France (2018).

39 Journées Hydrates, Brest, 09‐13 septembre 2019

Modification of formation kinetics and of gas selectivity in “artificial” sedimentary gas hydrates thanks to silica nano/micro‐beads.

C. Métais 1,2,3, J. Ollivier 1, L. Martin‐Gondre 2, A. Desmedt 3

1Institut Laue Langevin (ILL), Grenoble, France 2 Institut UTINAM, Besançon, France 3 Institut des Sciences Moléculaires (ISM), Bordeaux, France

Clathrate hydrates (also called gas hydrates) are nanoporous crystalline solids composed of hydrogen‐bonded water molecules forming cages within which gaseous molecules are encapsulated. They are naturally present on Earth, on permafrost regions and on oceans floors, but also on other comets and planets of the Solar System. [1] This natural occurrence makes them relevant for many geophysical and astrophysical applications [2]. In natural media, they are formed in the presence of sediments. What influence do these sediments have on the physico‐chemical properties and the formation of gas hydrates? Answering this question is of prime importance to fully understand the properties of these systems [3].

We have studied the properties of mixed gas hydrates, i.e., co‐encapsulating two gaseous species formed from CO2, N2 and CH4 gas mixtures. The substrate was an artificial environment, using silica beads (diameter ranging from 0.075 to 250 m) as an idealized environment to substitute to the natural sediments. Several properties have been investigated: the molecular selectivity (i.e. which gaseous specie is preferentially trapped), the gas diffusion at the silica/hydrate interface, the formation kinetics of mixed clathrate hydrates and the structural stability of these system. Both theoretical and experimental techniques have been used to study all these properties: Raman spectroscopy, quasi‐elastic neutron scattering, neutron diffraction, small angle neutron scattering and quantum mechanics DFT calculations.

The theoretical results made it possible to study the structural and energy stability of two pure hydrates as a function of the amount of gas trapped inside. In addition, the experimental results obtained show that the sediment surrogates have an influence on the properties of gas hydrates, such as the improvement of the molecular selectivity within the mixed hydrate or the strong modification of the formation kinetics. Some of these results will be presented and discussed.

[1] D. BROSETA, L. RUFFINE, A. DESMEDT Eds. Gas hydrates 1: Fundamentals, characterization and modeling. Wiley: London, 2017 [2] L. RUFFINE, D. BROSETA, A. DESMEDT Eds. Gas hydrates 2: Geosciences and applications. Wiley: London, 2018. [3] http://mi2c.hydrate.eu; website of ANR MI2C « Approche Multi‐échelle de l'impact d'impuretés minérales sur le piégeage de gaz dans des clathrates hydrates »

40 Journées Hydrates, Brest, 09‐13 septembre 2019

Etude cinétique et thermodynamique des hydrates de gaz en milieu poreux : applications aux hydrates sédimentaires et aux procédés de stockage du froid F.Benmesbah1,2, L.Ruffine1, P.Clain²,3, V.Osswald², O.Fandino‐Torres1, L.Fournaison², A.Delahaye²

1 IFREMER, Département Ressources physiques et Ecosystèmes de fond de Mer (REM), Unité des Géosciences Marines, 29280 Plouzané, France 2 IRSTEA, Département Ecotechnologie, Unité Génie des Procédés Frigorifiques, 1 rue Pierre‐ Gilles de Gennes, CS 10030; 92761 Antony Cedex 3Leonard de Vinci Pôle Universitaire, Research Center, 12 avenue Léonard de Vinci, 92916, Paris La Défense, France

Les hydrates de gaz sont abordés dans une grande variété de sujets scientifiques, notamment les géosciences et les procédés industriels tels que la production et le stockage du froid. Dans ces deux domaines en particulier, l’étude des mécanismes de formation et de dissociation des hydrates de gaz en milieux poreux est primordiale pour mieux comprendre la dynamique des hydrates de gaz présents dans les sédiments des marges continentales et optimiser les procédés de stockage du froid. La formation des hydrates de gaz dans des milieux poreux tels que le sable constitue un défi en raison des variations continues de perméabilité absolue et relative, le type de morphologie et l’hétérogénéité de la distribution des hydrates dans une telle matrice. Des paramètres tels que la saturation en eau, le débit d’injection du gaz, la taille des particules ainsi que la nature du milieu poreux peuvent affecter fortement les mécanismes liés à la formation des hydrates. Cette étude vise à comprendre l’effet de ces paramètres sur la cinétique de formation des hydrates et leur capacité de stockage du gaz en milieux poreux. Deux dispositifs expérimentaux, disponibles à Ifremer et Irstea, ont été utilisé dans le but de croiser les connaissances et les méthodologies développées dans les deux laboratoires, afin de générer des données complémentaires de cinétique et de thermodynamique, et ainsi mieux caractériser le processus de formation des hydrates en milieu poreux. A Ifremer, le premier dispositif développé consiste en une cellule haute pression pour étudier l’influence de trois paramètres : la saturation en eau, le débit volumique du gaz et la taille des particules de la matrice sableuse sur la cinétique de formation des hydrates et sur leur capacité de stockage du gaz. Les principaux résultats donnent des temps d’induction relativement aléatoire, confirmant le caractère stochastique de la formation des hydrates. La distribution des hydrates est également très contrastée d’une expérimentation à une autre, et cela, même en conservant les mêmes paramètres expérimentaux. Cette hétérogénéité s’observe dans la trajectoire de la pression dans le réacteur au cours de l’expérimentation. Ainsi, la distribution des hydrates semble aussi stochastique que le temps d’induction, empêchant ainsi une consommation totale de l’eau même dans des conditions d’excès de gaz. A Irstea, le second dispositif utilisé consiste en un banc d’analyse thermique différentielle développé spécifiquement pour caractériser les hydrates de gaz. Ce dispositif permettra l’étude de l’influence de la nature du milieu poreux sur la cinétique de formation des hydrates de gaz et leurs propriétés thermodynamiques.

41 Journées Hydrates, Brest, 09‐13 septembre 2019

Elastic parameters of hydrate‐bearing sands using DEM

A. I. Theocharis1, J.‐N. Roux1, V. Langlois1

1Laboratoire Navier, Université Paris‐Est, UMR 8205 (Ecole des Ponts ParisTech – Ifsttar – CNRS), Marne‐la‐Vallée, France

Hydrates are solid compounds, looking like ice, that include hydrocarbons trapped within a crystal structure of water. They are found underground and underwater most frequently in the form of hydrate‐bearing sands, are probably the largest source of hydrocarbons globally and could be part of a solution to global warming, whereas they also constitute a geohazard that may trigger catastrophic mechanical instabilities. In this work hydrate‐bearing sands are analyzed at their grain scale, focusing on their mechanical behavior and particularly their elasticity, using the Discrete Element Method. Based on the assumption that hydrate‐ bearing sands consist of grains and intergranular hydrate bonds, a new contact cement model is proposed for cemented spherical particles; this model is used in order to accurately measure the elastic properties of the material. A parametric analysis considering the density and coordination number of different DEM samples reveals how several microstructural variables affect the elasticity of the simulated materials. The significant parameters defining the elastic response of the material are found to be the mean bond stiffness and the coordination number (Fig. 1). Finally, the elastic results are compared with two well‐known mean field approaches, Voigt’s approach and Dvorkin’s Contact Cement Theory (CCT), in order to test the accuracy of these methods for hydrate‐bearing sands. Results show that Voigt results evolve similarly with what is observed in DEM and work clearly as an upper limit. Dvorkin’s CCT provides results which are systematically inaccurate with respect to DEM results no matter the assumptions on its critical variables.

(a) (b) Fig. 1: Elastic moduli (a) bulk and (b) shear of hydrate‐bearing sands for several DEM samples, normalized with mean bond stiffness, versus coordination number (a is the radius of the cement and d the particle diameter) (gc stands for grain coating)

42 Journées Hydrates, Brest, 09‐13 septembre 2019

Freshwater lake to salt water sea causing widespread hydrate dissociation in the black sea

V. Riboulot, S. Ker, et al.

IFREMER, REM‐GM, BP70, 29280 Plouzané, France

The Black Sea deserves attention for decades partly due to the fact that the Danube deep‐ sea fan is one of the largest sediment depositional systems in the world, and also because it is considered the world's most isolated sea, the largest anoxic water body on the planet and a prolific petroleum basin. Due to the high sediment accumulation rate with high input of organic materials from the Danube River, the Black sea sediment offshore the Danube delta is rich in microbial gas. Seismic data in the area show widespread occurrence of Bottom Seismic Reflector, indicative of extensive development of hydrate accumulations (Ker et al., 2019). The geomorphological analysis of the continental slope north‐east of the Danube canyon reveals complex sedimentary processes such as seafloor erosion and instability, mass wasting, gas hydrate accumulations and fluid migration features. The imprint of geomorphology seems to dictate the location of gas seeps (GHASS cruise, DOI: 10.17600/15000500). More than 1400 gas seeps within the water column have been detected between 200 m and 800 m water depth using acoustic records. Only 2% of gas flares were detected within the Gas Hydrate Stability Zone (GHSZ). At the landward termination of the GHSZ, numerous gas seeps within the water column are detected. These results suggest a geomorphological control of the degassing processes at the seafloor constrained by the occurrence of gas hydrates (Riboulot et al., 2017). In addition, the study of the gas hydrate dynamics in the Black Sea showed hydrate dissociation due to salt diffusion is the dominant process occurring between 660 m and 720 m of water depth (Riboulot et al., 2018). Indeed, the Black Sea was a freshwater lake before 9000 year B.P. After the reconnection with the Mediterranean Sea via the Bosphorus strait, the salinity content at the sea bottom increased up to the current concentration. Geotechnical simulation results, based on the analysis of a consistent multidisciplinary dataset, predict that recent and forthcoming salt diffusion within the sediment may destabilize gas hydrates by shrinking the extension and thickness of their thermodynamic stability zone. The communication will present scenarios of simulation on how the existing gas hydrate stability zone will evolve over time, and will subsequently trigger destabilization of gas hydrates covering at least 2800 square kilometres of the Black Sea margin. This process is predicted to occur in a region prone to kilometre‐scale slope failures which may trigger the release of 4.2 x 1010 to 2.1 x 1011 m3 of methane into the sea. Ker, S., Thomas, Y., Riboulot, V., Sultan, N., Bernard, C., Scalabrin, C., Ion, G., Marsset, B., 2019. Anomalously deep BSR related to a transient state of the gas hydrate system in the western Black Sea. Geochemistry, Geophysics, Geosystems 20, 442‐459. Riboulot, V., Cattaneo, A., Scalabrin, C., Gaillot, A., Jouet, G., Ballas, G., Marsset, T., Garziglia, S., Ker, S., 2017. Control of the geomorphology and gas hydrate extent on widespread gas emissions offshore Romania. BSGF‐Earth Sciences Bulletin 188, 26.

43 Journées Hydrates, Brest, 09‐13 septembre 2019

Riboulot, V., Ker, S., Sultan, N., Thomas, Y., Marsset, B., Scalabrin, C., Ruffine, L., Boulart, C., Ion, G., 2018. Freshwater lake to salt‐water sea causing widespread hydrate dissociation in the Black Sea. Nature communications 9, 117.

44 Journées Hydrates, Brest, 09‐13 septembre 2019

LIST OF POSTERS

45 Journées Hydrates, Brest, 09‐13 septembre 2019

46 Journées Hydrates, Brest, 09‐13 septembre 2019

Quantitative study of CO2‐CH4 and N2‐CH4 mixed clathrate hydrates using gas chromatography, Raman and IR reflectance spectroscopy: Application to icy moons E. Le Menn1, G. Tobie1, H. Marais1, D. Nna Mvondo1, A. Oancea1, C. Faugerolles1, O. Grasset1, S. Le Mouélic1

1 Laboratoire de Planétologie et Géodynamique, UMR‐CNRS 6112, Université de Nantes, France

Icy moons are complex water‐rich environments, where carbon dioxide, methane, nitrogen and other volatile species co‐exist with water ice and liquid water at depth. The existence of a massive atmosphere composed primarily of N2 and CH4 on Saturn’s moon Titan as well as the detection of CO2 and CH4 in the vapour plume emanating from the south pole of Enceladus suggests chemical exchanges with the icy surface and subsurface, potentially involving clathrate hydrates. Based on IR spectra of CO2 clathrate hydrate experimentally acquired at LPG (Nantes) (Oancea et al. Icarus 221(2012) 900‐910), CO2 clathrate hydrate has been identified at the surface of Enceladus (Combe et al. Icarus 317 (2019) 491‐508), which constitute the first detection of clahtrate hydrate outside the Earth. Future missions to Jupiter and Saturn’s systems may potentially reveal other gas clathrates. Acquiring reference data is essential for the analysis and interpretation of future observations. In this context, we have performed two series of experimentations on H2O‐CH4‐N2 and H20‐ CH4‐CO2 systems. Mixed clathrate hydrates were synthetized in control conditions using an autoclave coupled to a gas chromatographer. The molar composition of the synthetized clathrates for various gas composition were monitored using gas chromatography. We observe an enrichment of CH4 over the N2 in the considered range of reactant mole fraction (0.04 ≤ CH4 ≤ 0.7)(Nna MVondo et al. in revision). Preliminary results obtained on the CH4‐ CO2 system indicate an enrichment of CO2 in the considered range of reactant mole fraction (0. 4 ≤ CH ≤ 0.85). 4 For each synthesized sample, near‐infrared spectroscopy from 10000 – 2000 cm‐1 (1 to 5 μm) as well as Raman scattering from 50 – 4000 cm‐1 were carried out, in order to identify discriminating criteria for possible detection by remote and in‐situ observations of icy bodies of the outer Solar System. For each type of clathrate, we have identified the characteristic absorption band in the infrared. Our experimental results indicate that the identification of

CH4‐N2 binary clathrate and CH4‐CO2 clathrate is from IR reflectance spectra is possible, though challenging. It remains, however, difficult to constrain precisely the composition of detected clathrates. The best approach remains in‐situ Raman spectroscopy, which may be possible in future landing missions, such the Dragonfly mission to Titan just selected by NASA, or other missions to Europa, Enceladus and Triton currently under evaluation by NASA and ESA.

47 Journées Hydrates, Brest, 09‐13 septembre 2019

48 Journées Hydrates, Brest, 09‐13 septembre 2019

Influence of alkaline feldspars‐surrogates on the formation kinetic and the selectivity of

CO2‐N2 mixed hydrates: investigation by neutron scattering and Raman spectroscopy

Morgane LEMAIRE1,2, Marc DUSSAUZE2, Claire PETUYA3, Vivian NASSIF4, Bertrand CHAZALLON1, Arnaud DESMEDT2

1Univ. Lille, CNRS, UMR 8523 ‐ PhLAM‐ Physique des Lasers Atomes et Molécules, F‐59000 Lille, France 2Univ. Bordeaux, CNRS UMR 5255 ISM‐ Institut des Sciences Moléculaires, 33405 Talence, France 3JPL NASA PASADENA, 4800 Oak Grove Dr, 91109, Pasadena, U.S 4Institut Laue Langevin / Institut NEEL CNRS/UGA UPR2940, 38042 Grenoble, France

A lot of methods have been developed to extract hydrocarbons from hydrate‐bearing sediments.1,2 These different approaches based on promoting the in situ dissociation of gas hydrates, also produce some sand that leaded engineering, economic, environmental and safety issues.2,3 An alternative approach is the methane recovery by carbon dioxide replacement in natural gas hydrates. This method is more efficient with CO2‐N2 gas mixture, 3,4 instead of pure CO2, because of the preferential cage occupancy of the CO2. Petuya et al. 4 (2018) showed that, for this gas mixture, the N2 would not impede the hydrate formation and CO2 may trigger mixed hydrate formation. Because of the industrial relevance, special interest is given to the natural sediment influence on this mixed hydrate. Natural gas hydrates are found more easily in coarse sediments whose size exceeds 125 μm thanks to the grater permeability but with a low formation kinetic. When the grains are less than 125 μm, the mineralogical surface in contact with water and gas is increased thus promoting gas hydrate formation.5 Aluminosilicates (sodium, calcium and potassium feldspar) are minerals with Si‐Al substitution and charged with alkaline. This replacement allows them to have both 6 larger reaction and hydrophobic surface, promoting CO2‐hydrate dissociation. Our recent study, using the high‐resolution neutron two‐axis powder diffractometer (D1B‐ILL) showed that alkaline surrogates (sodium and calcium silicate) act like inhibitor of the induction time but allow to reach the diffusion plateau faster than a silica powder substrate. This inhibitory behaviour on the formation kinetics of CO2‐hydrate and CO2‐N2 mixed hydrate may be attributed to reactions between the surrogate, the ice and the host gas. Indeed, the alkaline‐ silicate surrogate could interact with the carbon dioxide and the ice to form some carbonates, that act like an inhibitor of hydrate formation. Moreover, additional investigations using Raman microspectroscopy, shows that carbonate formation is recurrent, both with sodium and calcium silicate. In order to further investigate their influence on gas hydrate properties, the selectivity studies were carried out with 50%CO2‐N2 mixed gas hydrate, showing that the presence of alkaline ions influenced this parameter by decreasing

CO2 selectivity. Indeed, the more the surrogate is charged with alkaline, the more the mixed

49 Journées Hydrates, Brest, 09‐13 septembre 2019

hydrate is selective in N2. Thus, the chemical composition of the surrogates, in particular the alkaline, plays a key role in the gas hydrates formation. Acknowledgements: This work is supported by ANR‐15‐CE29‐0016 MI2C. References: (1) Moridis G. J. et al, SPE Reservoir Eval. Eng. 2009, 12 (5), 745−771. // (2) Boswell R., Fire in the ice, 2013, 412, 386‐7614, http://www.netl.doe.gov/ research/oil‐and‐ gas/methane‐hydrates/fire‐in‐the‐ice. // (3) Qin J. and Kuhs W.F., J. Chem. Eng. Data, 2015, 60, 369–375. // (4) Petuya C. et al., Chem. Commun. 2018, 54, 4290‐4293. // (5) Sun S. C. et al., J CHEM Thermodyn. 2014, 69, 118‐124. // (6) Kumar A. et al., Fuel. 2013, 105, 4175‐ 4187.

50 Journées Hydrates, Brest, 09‐13 septembre 2019

Using quantum mechanics modeling for investigating the structural properties of strong acid hydrates

S. Espert 1,2, D. Sanchez Portal2, A. Desmedt 1 1 Groupe Spectroscopie Moléculaire, ISM UMR5255 CNRS ‐ Univ. Bordeaux, 33405 Talence, France 2 Centro de Física de Materiales CSIC‐UPV/EHU and DIPC, Paseo Manuel de Lardizabal 5, E‐ 20018, Donostia – San Sebastián, Spain.

Designing new devices dedicated to energy storage and production is at the center of nowadays concerns. In this area, the development of new electrolyte is of prime importance. Clathrate hydrates systems represent an opportunity as a new electrolyte for fuel cells recently patented [1], for which fundamental questions are opened. Clathrate hydrates are nanoporous ice‐like structure, where H‐bonded water molecules form cages within which guest molecule can be trapped [2]. These systems possess interesting properties depending on the nature of the invited molecules, due to their nanostructuration and to their specific physical‐chemistry properties [3]. In the case of gas hydrates, the guest molecules are gaseous species and new approaches for gas storage and separation (CO2, CH4, H2 etc) are thus developed [4]. When acidic species are encapsulated, clathrate hydrates are classified as super‐protonic conductivitor, due to the encapsulation of anionic species generating delocalized protons into the cationic cage network [5,6,7]. The best conductivity is found for strong acid molecules and more specifically for the HPF6 hydrates [8,9].

One important issue in the HPF6 hydrates is associated with the existence of impurities (e.g. H3PO4) due to the high reactivity of the fluorine anion. They have been identified by means of Raman scattering and conductivity measurements reveal the importance of these impurities in the proton mobility [8]. Locating these impurities at a molecular scale is a fundamental question for improving the electrolytic properties of the strong acid hydrates. Quantum mechanics calculations are appropriated tools for investigating such a property in the Density Functional Theory (DFT) approximation. The stability of the strong acid hydrates including impurities has been computed for various DFT parameters. One of the challenge was to select the appropriated functional for describing a system exhibiting weak interactions such as H‐bond, together with strongly localized ionic interactions between the species. These calculations yield to construct a stable strong acid hydrate incorporating impurities. This static model can then be used to perform molecular dynamics (MD) simulations in order to introduce the kinetic energy in addition to the potential energy to reproduce the hydrate. To take into account for the ionic character of the system, these simulations have been performed in the frame of the first principle approximation by means of DFT‐MD simulations. It yields to produce atomic trajectories reproducing the proton mobility and thus provide information to understand the underlying factors governing the super‐protonic conductivity mechanism. The validation of this advanced quantum mechanics calculations is envisaged in the near future, through the comparison of MD‐derived scattering laws with experimental ones obtained by means of (quasi‐elastic) neutron scattering.

51 Journées Hydrates, Brest, 09‐13 septembre 2019

[1] Desmedt et al, patent FR 18 53886, 4 may 2018. [2] E.D. Sloan and C.A. Koh, Clathrate Hydrates of Natural Gases, 2008; Taylor & Francis‐CRC Press: Boca Raton, FL. [3] Broseta et al, Gas hydrates 1: Fundamentals, Characterization and Modeling, 2017; WILEY‐ISTE, London. [4] Ruffine et al, Gas hydrates 2: Geosciences and Applications, 2018; WILEY‐ISTE, London. [5] Desmedt et al, J. Chem. Phys. 121(23) (2004) 11916–11926 [6] Desmedt et al, Solid State Ionics, 252 (2013) 19‐25 [7] Bedouret et al, J. Phys. Chem. B, 118 (2014) 13357‐13364. [8] Cha et al, J. Phys. Chem. C,112 (2008) 13332‐13335. [9] Desplanche S., PhD Univ. Bordeaux (2018) – articles in preparation.

52 Journées Hydrates, Brest, 09‐13 septembre 2019

Study of Methane Hydrate Formation in Fontainebleau Sand Using X‐Ray Computed Tomography L. Bazinet1, F. Benmesbah1,2, M. Rovere1, O. Fandino1, L. Ruffine1, L. Fournaison², A. Delahaye², P. Clain², 3, V. Osswald²

1 IFREMER, Dép Ressources Physiques et Ecosystèmes de Fond de Mer (REM), Unité des Géosciences Marines, 29280 Plouzané 2 IRSTEA, Dép Ecotechnologie, Unité Génie des Procédés Frigorifiques, 1 Rue Pierre‐Gilles de Gennes, CS 10030; 92761 Antony Cedex 3 Leonard de Vinci Pôle Universitaire, 12 Av Léonard de Vinci, 92916, Paris La Défense

Natural gas hydrates occur abundantly in nature, such as in the Artic regions and in marine sediments. The formers grow in the oceanic slopes of the continental margins at water depths in between 350 and 5000 meters and they entrapped a large amount of gas primarily formed by microorganisms that live in the deep sediment. The massive hydrate dissociation could lead to a landslide or slope failure resulting in an instability of the oil platforms or, due to their proximity to the cost, even tsunamis. Often marine gas hydrates are associated with chemosynthetic communities living at cold seeps as they represent a tremendous reservoir of methane used for energy. In nature, the hydrate distribution is a function of several parameters such as the mineralogy of the sediment, the degree of saturation in water and the mode of transport of the gas in the porous space. The study of the influence of these parameters on the distribution of hydrates would make it possible to better estimate their volume in marine sediments.

Amongst potential applications of gas hydrates being under investigations include industrial processes such as cold storage and distribution in refrigeration. The use of a porous medium will influence the hydrate formation kinetics and will work as a hydrate promoter without altering their stability. Understanding the mechanisms of hydrate formation in porous media are key for the optimization and exploitation of novel refrigeration systems.

The objective of this work, led both by Ifremer and Irstea, is to study the influence of the degree of saturation in water on the distribution of methane hydrates. Hydrates are formed in a matrix of Fontainebleau sand with different degrees of saturation using a high‐pressure cell equipped with separated gas and water injection devices in order to reproduce the seafloor fluid circulation. Water and hydrate distribution in the porous media are analyze by X‐Ray Computed Tomography. In this communication, we will present the methodology developed for the CT Scan analysis, and preleminary results from recent experiments.

53 Journées Hydrates, Brest, 09‐13 septembre 2019

54 Journées Hydrates, Brest, 09‐13 septembre 2019

NOTES

55 Journées Hydrates, Brest, 09‐13 septembre 2019

56 Journées Hydrates, Brest, 09‐13 septembre 2019

57 Journées Hydrates, Brest, 09‐13 septembre 2019

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