These research projects structured around 4 cross-disciplinary scientific work packages (WPs) that address the fundamental question of how complex rheologies influence the dynamics of both the shallow and the deep Earth and industrial applications. Interdisciplinarity is ensured by three means: (1) by the association in all WPs of projects focusing on fundamental and applied problems, (2) via the academic and industrial secondments, which involve the use of different methods and work in different environments, and (3) by collaborations between ESRs working on similar objects/questions, but with different methods (transverse research themes). These transverse research themes, which will be jointly animated by a senior researcher and an ESR, are:
- Mantle dynamics and plate tectonics, which reunites ESR’s projects 1, 6, 7, 8, 9, 11, 15, 16
- Multiple deformations mechanisms and composite rheologies, which includes ESR’s projects 1, 3, 5, 7, 8, 10, 11, 16.
- Faults rheology and dynamics, which includes ESR’s projects 2, 4, 6, 10, 14, 16.
- Fluid-rock interactions, which includes ESR’s projects 3, 8, 12, 14
- Rocksalt deformation, which includes ESR’s projects 3, 13
- Microfracturing and induced seismicity, which includes ESR’s projects 2, 12, 14.
- Deformation and anisotropy of physical properties, which includes ESR’s projects 1, 6, 11, 13.
WP1: Experimental characterization of complex rheologies - Coordinators: D. Mainprice (CNRS-GM) & C. Spiers (UU)
This WP groups 5 projects centred on the experimental characterization of rheology in the laboratory.
ESR1 Rheology of the lithospheric mantle.
Supervisors: S. Demouchy, D. Mainprice (CNRS-GM). Secondments : Univ. Durham & Schlumberger
Objectives: Constrain the rheology of the lithospheric mantle through deformation experiments on olivine single crystals and aggregates at 800-1100°C and pressure ~ 300MPa via deformation experiments in a Paterson Press
Expected Results: Flow laws for the lithospheric mantle; experiments performed to variable finite strain will allow to analyse the hardening behaviour and the strain localization due to interactions between the crystal anisotropy and the boundary conditions. Microstructural characterization by SEM-EBSD (Montpellier) and TEM (coll. P. Cordier, Univ. Lille) will permit correlation of the mechanical behaviour with the evolution of the intracrystalline strain fields and dislocation structure. In-situ analysis of microseismicity during the experiments will allow characterizing the ductile-brittle transition.
ESR2 Effects of fault rheology on microseismicity.
Supervisors : A. Niemeijer,H. Paulssen (UU).Secondments : Univ. Bristol & Baker Hughes
Objectives: Assess potential hazards associated with induced seismicity by (1) investigating the effects of fault rheology on microseismic (acoustic emission) signatures in the laboratory, focusing on the factors that control nucleation of aseismic versus microseismic rupture at low slip velocities; (2) comparing laboratory-scale microseismicity with records of reservoir-scale seismicity from oil, gas and geothermal fields
Expected Results: Identification of the factors controlling the transition from aseismic to (micro)seismic slip on fault rock materials relevant to the oil, gas and geothermal energy industry. Develop a better understanding of the scaling relations for seismic events from the laboratory to the reservoir scale.
ESR3. Quantifying the role of coupled solution transfer and frictional/brittle processes in controlling the rheology, transport and containment properties of rocksalt.
Supervisors: C. Spiers, S. Hangx (UU). Secondments : UCL & AkzoNobel
Objectives: This project aims a) to develop mechanism-based models describing porosity-permeability development in deforming salt due to competition between fluid-assisted crack growth and crack healing/sealing processes, b) to determine the influence of these processes on creep, and c) to determine how fluid-phase additives can be used to manipulate the mechanical and transport properties of salt. The results obtained will be relevant to better predicting the stability and containment capacity of solution-mined storage caverns in rocksalt, the flow properties of granular salt products and the behaviour of crustal rock and fault systems under hydro- or geothermal conditions.
Expected Results: New, quantitative, mechanism-based constitutive models describing the rheological behaviour, transport properties and containment capacity of rocksalt in the regime where fluid-assisted microcracking and crack healing/sealing compete, and where pressure solution and sintering (neck growth) effects compete with frictional granular flow.
ESR4. The role of diffusion creep mechanisms, activated at seismic slip rates by frictional heating, in controlling dynamic fault weakening and earthquake propagation.
Supervisors: N. De Paola, S. Nielsen, R.E. Holdsworth (UDUR) Secondments : Geosciences Montpellier & Geospatial Research Ltd.
Objectives: Preliminary results from high velocity friction experiments, performed in the Rock Mechanics laboratory at Durham, show that superplastic flow may control the strength of fine-grained rocks deforming at high strain rates and temperatures. This project aims to: 1) Describe the friction of earthquake faults by experiments at seismic slip rates; 2) Constrain strain rates and temperatures leading to activation of diffusion creep by microstructural analyses on the nanoscale material of experimental and natural slip zones; 3) Model the flow stresses predicted by diffusion creep constitutive laws, using natural and experimental slip zones parameters, and compare them with those values measured in the laboratory. The results obtained will be used to test whether the activation of grain size-sensitive diffusion creep mechanisms can account for the weakening of faults observed in experiments performed at seismic slip rates.
Expected Results: A better understanding of earthquake propagation processes in the upper crust by the proposition of a new, mechanism-based model to explain the observed weakening of faults, when deforming at seismic slip rates, by the activation of grain size-sensitive, diffusion creep mechanisms. The expected results may impact on seismic risk assessments.
ESR5. Rheology and deformation of glass under extreme conditions.
Supervisors: B. Kaus (JGU) & C. Kunisch (Schott). Secondments : Geosciences Montpellier
Objectives: The rheology of glass is essentially measured by indentation tests at room temperature, but the present picture is too coarse, as the deformation is heterogeneous and the actual pressure and temperature beneath the indentor tip cannot be measured. The proposed association of numerical models and experiments at elevated temperatures (below the glass transition temperature) and moderate pressure with precise determination of both strain and stress will allow to determine the influence of pressure on the glass mechanical behaviour. This will lead to a better understanding of how glass interacts with other materials (such as metals) and open the possibility to use glass for new (and extreme) industrial applications.
Expected Results: Constrain the rheology of various glass types under high pressures
ESR10 . Creep of granular materials: from fault gouge to reservoir rock.
Supervisors: T.M. Mitchell , P.G. Meredith, N. Brantut (UCL). Secondments: Univ. Utrecht & Geospatial research Ltd
Objectives: (1) Characterization of the microphysical deformation processes associated with creep of granular aggregates (quartz and phyllosilicates) under pressure and temperature conditions commensurate with those at depth in the brittle crust. (2) Quantification of the evolution of associated physical and transport properties; compressional and shear wave velocities, acoustic emission statistics and locations, and permeability. (3) Development of a physics-based rate-dependent constitutive deformation model to enable extrapolation of experimental data to crustal spatial and timescales
Expected Results: New and unique holistic datset describing rate dependent deformation of granular aggregates. A fully coupled fluid flow and deformation model. Model outputs describing granular deformation in fault zones and reservoirs.
WP 2: Laboratory modelling of complex rheologies - Coord.: F. Funiciello (UniRoma3) & A. Davaille (CNRS-FAST)
The 3 projects that compose this WP have in common the use of physical models and analog materials to study the effects of the complex rheology of Earth materials on the planet dynamics.
ESR6. Unraveling the subduction earthquake cycle through analogue modelling and the analysis of natural data.
Supervisors: F. Funiciello (UNIROMA3). Secondments: Geosciences Montpellier & MP Strumenti
Objectives: Constrain the role of the rheology of the subduction plane and of the underlying mantle on the subduction earthquakes cycle by (1) formulating a conceptual model for the earthquake cycle, based on statistical analysis of natural data from convergent margins; and (2) validating the model by means of scaled laboratory experiments using a broad range of materials with different rheologies
Expected Results: A conceptual model for the earthquake cycle based on rheological laws for subduction plane and of the underlying mantle
ESR7. Convective instabilities in colloidal dispersions.
Supervisors: N. Ribe & A. Davaille (CNRS-FAST). Secondments: Univ. Mainz (JGU)& SCHOTT
Objectives: Investigate the origin and morphology of convective instabilities in colloidal dispersions, using a model rheology based on the extensive rheometrical database that has been built up at FAST since 2010
Expected Results: A better understanding of the rheology of aqueous silica colloidal dispersions as a function of the concentration of the dispersed phase; a better understanding of the physical processes producing of plate tectonics in the laboratory models and in the Earth.
ESR8. From viscous plumes to dikes and fractures: influence of the rheology on the lithospheric response to planetary mantle upwellings.
Supervisors: A. Davaille (CNRS-FAST). Secondments: ETH & Reykjavik Geothermal
Objectives: Investigate the conditions responsible for the different responses to mantle plume impacts, including volcanic plateaus, volcanoes, triple-junction rifting, and coronae by laboratory experiments using polymer gels and colloids, whose rheologies combine viscous, elastic and plastic aspects.
Expected Results: Regime diagrams and scaling laws derived from the experiments will allow the results to be applied to planetary dynamics.
WP3. Numerical modelling of complex rheologies - Coord.: B. Kaus (JGU) & P. Tackley (ETH)
This WP reunites 5 numerical modelling projects. Three of these projects analyze the role of history-dependent rheologies on plate tectonics and mantle convection. The fourth project works on a shorter time and smaller spatial scale, focusing on the interactions between fluids and deformation in geothermal reservoirs.
ESR9. Plate tectonics: strain localization due to anisotropy in the lithospheric mantle.
Supervisors: A Tommasi (Geosciences Montpellier). Secondments: ETH & APERAM
Objectives: Investigate the role of an anisotropy of physical properties due to preferred orientation of olivine crystals in the lithospheric mantle on global plate tectonics using a 3-D multiscale approach combining finite-element models of lithosphere-scale deformation with viscoplastic self-consistent simulations of evolving anisotropic physical properties. For this, we will develop new modelling routines for simulating the evolution of mechanical anisotropy function of the deformation history. These models will be used for studying the reactivation of lithospheric structures on the formation of new plate boundaries.
Expected Results: A better understanding of the processes allowing for strain localization in the ductile regime; a parameterized description of deformation-induced mechanical anisotropy that can be incorporated into 3-D convection codes.
ESR12. Modelling crack propagation and fluid injection (hydrofracturing) applied to geothermics.
Supervisors: B. Kaus (JGU) & H. Deckert (IGEM). Secondments: Univ. Bristol & GMuG
Objectives: (1) Develop new software to model hydrofracturing in heterogeneous viscoelastoplastic rocks in 3D using massively parallel high-performance computers; (2) Perform systematic simulations to understand how stress states and heterogeneities affect crack propagation, (3) Compare the simulations with natural data and (4) with laboratory experiments
Expected Results: A new massively-parallel 3D code capable of simulating hydrofracturing in poro-viscoelastoplastic rocks and allowing to quantify how hydrofracturing influences the local state of stress and the effective rheology of the reservoir
ESR15. Large-scale mantle dynamics: Influence of evolving microstructures.
Supervisors: P. Tackley, T. Gerya (ETH). Secondments: Univ. Mainz (JGU) & Rockfield
Objectives: Investigate numerically how evolving grain texture, including grain size and alignment (anisotropy) influences three different aspects of plate tectonics and mantle dynamics: (i) how reactivation of previous plate boundaries, in particular continental rifting, is influenced by history-dependent rheology arising from microstructural properties (ii) how lithospheric weakening may be caused by grain evolution including pinning by minor phases, (iii) the influence of grain-size evolution and anisotropy on large-scale mantle dynamics, including weakness of subducting slabs caused by grain-size reduction at phase transitions, and deep mantle anisotropy
Expected Results: New models allowing to study the feedbacks between microstructural evolution and rheology, A greater understanding of the role of microstructural evolution on the arisal of plate tectonics.
ESR16 . Rheological controls of seismicity along lithospheric plate boundaries.
Supervisors: T. Gerya, P. Tackley, Y. van Dinther (ETH). Secondments: Uniroma TRE & Schlumberger
Objectives: Investigate the rheological controls of spatio-temporal variability of seismicity along convergent, divergent and transform plate boundaries using a seismo-thermo-mechanical (STM) geodynamic modelling approach, comprising 3 steps: (i) modelling long-term seismicity patterns for three different lithospheric boundary types and understand differences between them, (ii) modelling transient seismicity associated with emerging plate boundaries (iii) studying how history-dependent rheology arising from brittle fracturing, microstructural changes, hydration/dehydration reactions and fluid/melt percolation affects the spatiotemporal variability of seismicity.
Expected Results: Gain insight into the evolution of seismicity distribution and earthquake cycles at plate boundaries.
WP4. Seismological investigations of deformation and rheology - Coord.: C. Thomas (WWU) & J.M. Kendall (UBRIS)
The 3 projects that compose this WP have in common the use of seismic anisotropy to indirectly study the deformation and the rheology in the Earth.
ESR11 . Anisotropy and structure of the D" region.
Supervisors: C. Thomas (WWU). Secondments: Univ. Bristol & GMuG
Objectives: Objectives: Constrain the convective flow pattern and the rheology at the base of the lower mantle (D" layer) via a systematic search for reflectors from/within D" using recently developed array techniques and source- and receiver arrays. Interpretation of the amplitude, polarity, and frequency content of the reflections from different azimuths sampling one region through calculated reflectivity based on mineral physics constraints and geodynamical models.
Expected Results: Map of D" anisotropy and flow pattern for several regions and knowledge of influence of mantle convection on development of anisotropy. Constraints on D" mineralogy through detected anisotropy.
ESR13 . Development of seismic anisotropy in deforming salt bodies.
Supervisors: J.Wookey (UBRIS). Secondments: Univ. Bristol & GMuG
Objectives: Objectives: The precise location of salt bodies by seismic methods is fundamental in petroleum exploration, as oil and gas accumulate below or along their flanks. Rocksalt has very different properties from surrounding sediments; it is generally higher in seismic velocity, lower in permeability and lower in density and viscosity, what leads to upward mobility in the form of sheets and diapirs. Flow results, however, in seismic anisotropy, which has to be considered in the treatment of the seismic data. The aim of this project is to develop multiscale models for predicting crystal preferred orientations produced by rocksalt deformation in sedimentary basins and the resulting seismic anisotropy.
Expected Results: Better seismic imaging of salt bodies, which often form oil and gas traps .
ESR14 . Seismic methods to estimate the strength of cracks and fractures.
Supervisors: J.M. Kendall, J.P. Verdon (UBRIS). Secondments:UCL & Reykjavij Geothermal
Objectives: Objectives: Use of seismic anisotropy to monitor the evolution of cracks and fractures and the resulting secondary porosity and fluid flow in reservoirs. The ESR will will develop methods for fracture characterisation using measurements of seismic anisotropy and attenuation and apply these methods for analysing recently collected microseismic datasets from two distinct settings: an oil reservoir where hydraulic fracture stimulation has been monitored; a naturally fractured geothermal reservoir on a deforming volcano, where microseismic events have been located and calibrated. A specific interest is in recently developed methods to estimate fracture compliance, which is a key indicator of permeability in these settings.
Expected Results: New methods for monitoring the spatial and temporal the evolution of cracks and fractures and its effect on the secondary porosity and fluid flow in reservoirs.