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Geomechanics and energy

The Geomechanics and energy research axis covers the following applications : Geological radioactive waste disposal, CO2 geological storage, Petroleum geomechanics, Marine geotechnics.

Geological radioactive waste disposal

(Y.J. Cui, P. Delage, S. Ghabezloo, J.M. Pereira, A. Pouya, J. Sulem, A.M. Tang)

These research works are performed in collaboration with ANDRA, CEA, ONDRAF/EURIDICE (Belgium) and NAGRA (Switzerland) in the framework of different projects (TIMODAZ European project (2006-2010) and the participation in Geomechanics research laboratories group of ANDRA 2007-2010 and 2011-2014). These research works focus on the behaviour of engineered and geological barriers (clays and argillaceous rocks) with a particular attention to the role of thermo-hydro-mechanical (THM) couplings and damage on their sustainability and long term sealing.

TIMODAZ European project (2006-2010) focused on the impact of the temperature on the behaviour and damage of argillaceous rocks (Ph.D. thesis of Mohammad Monfared, ALERT Geomaterials European Ph.D. prize 2011). In this framework a new hollow cylinder triaxial apparatus has been developed for studying the THM behaviour of very low permeability materials. The experimental results confirmed the self-sealing capacity of the cracks in argillaceous materials and the possibility of the reactivation of the plans of mechanical weakness by thermal pressurization of the pore fluid. The contraction of an argillaceous rock under an increasing temperature (similar to the case of normally consolidated clays) and also a thermal hardening phenomenon have been demonstrated for the first time. The same triaxial apparatus has been used for study of the Callovo-Oxfordian argillaceous rock (COx) from the underground laboratory of ANDRA at Bure (Ph.D. thesis of M. Mohajerani, 2001 and H. Menaceur started in 2011).

In collaboration with the Belgian National Agency for Radioactive Waste (ONDRAF/EURIDICE), the time-dependent behaviour of the Boom clay (Ph.D. theis of Le, 2008) and also the effect of salinity on the hydro-mechanical behaviour of clays from various potential storage sites (post-doc of Deng, 2009, Ph.D. thesis of X.P. Nguyen, 2013) have been studied. An elasto-plastic modelling of the thermo-mechanical behaviour of the hard clays has been performed (Ph.D. thesis of Hong, 2013). The anisotropic behaviour of the Boom clay is also studied in the Ph.D. thesis of Dao (started in 2011) and the behaviour of the Boom clay/compacted bentonite interface is studied in the post-doc of Chen (2012).

Afin d’évaluer la possibilité d’utiliser l’argilite broyée comme matériau de scellement pour le stockage de déchets nucléaire sur le site de Bure, une étude a été réalisée, en collaboration avec l’ANDRA, sur le mélange argilite broyée/bentonite MX80 ensuite (thèse de Wang, 2012). Les résultats obtenus ont montré le rôle dominant de la bentonite sur la pression de gonflement du mélange et les interactions physico-chimiques entre différents matériaux et fluides. In collaboration with IRSN, the hydro-mechanical behaviour of a bentonite/sand mixture has been studied (Ph.D. thesis of Wang, 2012). This study has then been extended to the long-term behaviour through identification of the microstructural evolutions of the soils with different initial states (Ph.D. thesis of S. Saba, started in 2010). The thermo-hydro-mechanical modelling of damage-plasticity coupling in multiphase porous media has been developed (Ph.D. thesis of C. Arson, ALERT Geomaterials European Ph.D. prize 2010 and S. Le Pense, started in 2010). The hydro-mechanical behaviour of the excavation damaged zone (EDZ) has also been studied by development of equivalent continuous models and analytical and numerical homogenization methods. The equivalent permeability of the unsaturated cracked porous media has also been studied and analytical and numerical solutions have been obtained.

CO2 geological storage

(S. Ghabezloo, J.M. Pereira, A. Pouya, J. Sulem, in collaboration with T. Fen-Chong from Porous media team and M. Vandamme from Multi-scale team)

The researches on CO2 geological storage are performed in the framework of ANR, ADEME and CO2 chair projects and collaborations with Total, BRGM, ENTPE. Within Navier laboratory, collaborations are conducted with Porous media and Multi-scale teams. The research works concern the experimental characterization and modelling if the coupled THCM behaviour of the interface between the materials of the storage site (cement, reservoir rock, cap-rock) (Ph.D. thesis of V. Vallin, started in 2010), study of the influence of drying induced by CO2 injection in the reservoir rock on its hydro-mechanical properties (Ph.D. thesis of F. Osselin, started in 2010), modelling the equivalent permeability of cracked porous media (Ph.D. thesis of M.N. Vu, 2012), evolution of the fracture properties of rocks in contact with CO2 (Ph.D. thesis of G. Suhett-Helmer, started in 2011), hydro-mechanical behaviour of faults and induced seismicity during CO2 injection (FISIC ANR project, Ph.D. thesis of V.L. Nguyen, started in 2012), CO2 injectivity in coal bed (post-doc of N. Espinoza).

An experimental device for simultaneous percolation of supercritical CO2 and brine in rocks under realistic stress and temperature conditions has been developed. This apparatus is used for studying the effect of pore network clogging and/or solid matrix damage due to the crystallization of the salt initially dissolved in the brine. A thermodynamics and poromechanics framework of salt crystallization in the context of CO2 storage has been developed.

Petroleum geomechanics

(J. Canou, P. Delage, J.C. Dupla, S. Ghabezloo, J. Sulem)

This research area is developed in collaboration with Total, IFPEN, IFSTTAR, university of Lille on different issues including the behaviour of oil-well cements, exploitation of oil sands by steam injection (SAGD : Steam Assisted Gravity Drainage), produced water re-injection, evaluation of the permeability of reservoir sands.

The research carried out on the integrity of cement lining in oil wells, submitted to various coupled mechanical and thermal loadings, during oil production and CO2 storage in depleted reservoirs, has been conducted since 2005, in particular in collaboration with Total, within the framework of three consecutive Ph.D. thesis (S. Ghabezloo, 2008, Ph.D. prize of ENPC and Ph.D. prize of Université Paris-Est, Ph.D. thesis of M.H. Vu, 2011 and Ph.D. thesis of N. Agofack, started in 2010). The study of the behaviour of oil-well cements in well conditions (high pressure, high temperature) is performed by combining laboratory experiments, microstructural characterization and observation, homogenization methods and also theoretical and numerical analysis and modelling. These studies are performed on the behaviour of hardened cement paste and also the behaviour of cement paste during hydration under thermo-hydro-mechanical solicitations. Within the framework of a Ph.D. thesis (D.H. Doan, 2011) in collaboration with IFPEN on the steam-assisted gravity drainage (SAGD) of Athabasca oil sands (Canada), a detailed investigation has been performed on the damage induced to the sand by gas exsolution. The phenomenon of progressive clogging of the granular structure of sandy oil reservoirs, and corresponding permeability reduction has been observed during the re-injection of the produced water. In collaboration with Total, an experimental and theoretical research is conducted on the transport and deposition of solid particles in a porous medium under fluid flow (Ph.D. thesis of S. Feia, started in 2011).

Marine geotechnics

(P. Delage, J.M. Pereira)

This research focuses on the evaluation of the geotechnical risks related to the presence of gas in marine sediments (CITEPH projects, CLAROM industrial consortium, post-docs of S.S. Torisu, 2009-2010 and D. Manzanal, 2011-2012). It is aimed to characterize the behaviour of deep marine sediments for optimisation of the offshore foundations design and the stability of sub-marine slopes. An empirical model taking into account the microstructure breakdown and time dependent effects has been developed in collaboration with Hong-Kong University (Béatrice Baudet). This model has then been implemented in a finite element code taking into account the presence of dissolved or free gas.

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