Research
Catherine Noiriel - Associate Professor, Geochemistry and Reactive transport

My research objectives are to improve the understanding of reactive fluid transfers in reservoir rocks. I try to couple together experimental approaches to numerical modelling. I am interested in developing new tools to investigate hydro-chemical and mechano-chemical processes at the pore scale, with applications to environmental and energy issues such as geothermy and CO2 geological storage in order to mitigate climate change. From the experimental point of view, I am a huge fan of 3D X-ray micro-tomography imaging to characterise evolving geometries through time, and quantify mineral or rock reactivity. 

Main research thems include:

++ Flow and reactive transport modelling in porous rocks and fractures
++ 3D Characterization of fracture and porous rock geometry using 3D X-ray micro-tomography
++ Fluid-rock interactions, focusing on dissolution and precipitation rates of minerals
++ CO2 sequestration in geological reservoirs (carbonates and sandstones)
++ Geothermal energy recovery and sustainability improvement
++ Crytal growth, crystallization pressure, and rock damaging
 



Tracking the dynamics of the fluid-mineral and fluid rock interfaces

Fluid–mineral and fluid–rock interfaces are key parameters controlling the reactivity and fate of fluids in reservoir rocks and aquifers. The interface dynamics through space and time results from complex processes involving a tight coupling between chemical reactions and transport of species as well as a strong dependence on the physical, chemical, mineralogical and structural properties of the reacting solid phases. In an article written with Cyprien Soulaine, we review the suitability of time-laspe X-ray micro-tomography imaging to track the fluid-solid interface. We also evaluate direct modelling of reactive transport from 3D digital rocks to better understand coupling between chemical reactions and flow and transport processes. See
Noiriel and Soulaine [2021] for more details.

interface
Extraction and mapping of a 333x333 µm2 fluid-rock interface from XMT imaging, and evolution of the topography with chemical processes


Geochemical reactivity of crystals and minerals

Discrepancies between kinetic rates determined in well-controlled conditions -up to several orders of magnitude- have long been reported. 
Here, X-ray micro-tomography (XMT) allows for examination of the reaction rates at the whole crystal surface. XMT imaging was performed at the Swiss Light Source. Exploring reaction rates in 3D at the crystal surface constitutes a nice bridge between micro-scale surface topography observations (e.g., with Atomic Force Microscopy, AFM, or Vertical Scanning Interferometry, VSI) and powder studies in continuously stirred reactor, and is helpful to gain a broader and more unified picture of dissolution kinetics over multiple length scales. The method integrates the contribution of the crystal faces, edges and corners as well as of the different crystal features (etch pits, cleavage, parting planes, topographic lows, macrosteps...) to the whole dissolution process.
In particular, we have shown in two studies that the crystal edges were paying a large contribution to the dissolution process of calcite.
Also, a collaborative work with Damien Daval (University of Grenoble) has permitted to validate XMT
imaging of crystal surfaces against VSI. Even if the resolution of XMT is lower and some artifacts inherent to the technique exist, we have validated this imaging method for exploring reactivity of minerals in 4D.
See Noiriel et al. [2019] and Noiriel et al. [2020] for more details. 

calcite crystal geometry evolution  dissolution rate mapped at the surface
Crystal geometry evolution (calcite) obtained after dissolution experiments in a reactor, and 3D dissolution rate mapping at the crystal surface.

calcite crystal geometry evolution
Evidence of enhanced dissolution rates at the crystal edges and corners (calcite)


Reactive transport in evolving porous media and fracture sealing

Mass transfer in rocks
result from the coupled motion of fluid and dissolved species, and chemical reactions at the water-rock interface. Description of these processes relies on parameters to characterize both transport and surface reactivity. Numerical modelling at the continuum scale is based on the advection-dispersion equations for transport and a thermo-kinetic description derived from the transition state theory for chemical reactions. Applications of reactive transport modelling to evolving geometries rely on an accurate and physical description of how the relevant parameters used to estimate mass transfer evolve, i.e., porosity, permeability, specific surface area or crystal nucleation/growth.
I have worked recently with Nicolas Seigneur (Mines Paristech) to model precipitation and evaluate the sealing capacity in single fractures. Observations and reactions rates derived from calcite precipitaion experiments in natural limestone samples were used to constrain the reactive transport code Hytec. Two main points were accounted for:
Feedback betwen fracture aperture (or porosity) reduction and evolution of the flow velocity and permeability, until sealing is complete
Preferential nucleation (critical saturation index) of calcite onto calcite compared to other mineral substrates.
Results to be (hopefully) soon published!

figure_precipitation1

Figure: (left) Initial fracture geometry and (right) calcite volume fraction precipitated in a rough fracture, showing preferential precipitation in the areas (i) near the inlet, where the supersaturation is the highest, and (ii) in the main flowpaths, where the supply of reactants is higher.

figure_precipitation2
Figure: Difference in volume fraction of calcite precipitated and permeability field between (left) a continuum description of the fracture and consideration of substrate heterogeneity and nucleation limitations at the fracture walls (middle and left).

 




Precipitation in porous media

Precipitation of mineral phases can lead to a dramatic alteration of fluid transmissivity in porous rocks. It can be induced, for instance, by injection of fluids, CO2 degassing, drying, fluid temperature changes, or biological processess. Precipitation is a complex issue, as far as both nucleation and growth mechanisms at the mineral surface, which involve free energy barriers and specific arrangment of a crystalline lattice, are superimposed to the transport of the elements from and toward the mineral surface. Here, X-ray micro-tomography has permitted to examinate the precise
layout of the new crystals and the calculation of the growth rates within porous media. We have shown that precipitation is highly dependent to the substrate on which new crystals grow, thus affecting the reduction in rock permeability.
See Noiriel et al. [2012] and Noiriel et al. [2016] for more details. This work arises from a collaboration with Carl Steefel and Li Yang at Berkeley National Lab. Imaging was performed at the Advanced Light Source.

precipitation_beforeprecipitation-after    precipitation-thin-section
Layout of crystals and fluid-solid interface displacement during precipitation of calcite in a porous medium mimmicking a sandstone (packed glass beads and carbonate grains)

precipitation_before
Crystal growth rate determination at the surface of two different types of grains from precipitation of crystals in porous media. Reprinted from Noiriel [2015]


Crystallisation pressure and rock damages

Salt precipitation in porous media can exert a force, called crystallisation pressure, that can in turn deeply damage rocks by generating new fracture networks. In this study realised during my post-doc (Noiriel et al. [2010]), we have 
examined with X-ray tomography the damages caused by salt in several porous rocks in order to better understand this coupled mechano-chemical process. The results show a high fracturation density in sandstones and limestones, leading to the creation of new preferential flow paths. 


Vosges' sandstone
Salt growth (with) and fracture-induced damage in a porous sandstone (Vosges' red sandstone)


3D fracture geometry characterisation and changes during dissolution

Fractures, which develop in low permeability rocks, are the principal path for water flow and potential contamination. I have extensively studied the 3D geometry of fractures in different rocks during reactive transport experiments, while measuring the different properties controlling the fracture permeability, such as hydraulic aperture, mechanical distribution, or surface roughness. Caracterisation of surface roughness and aperture involve different approaches (statistical parameters, fractal approch through the Hurst exponent, etc.).
fractures       Fracture walls and aperture
Example of fracture geometry evolution during            Cartography of fracture walls and aperture (2x2 mm)
dissolution (2x2 mm)

Dissolution can occur when natural environments are subject to chemical disequilibrium. This process leads to modifications of fracture topology and transmissivity by reactive fluids. Here, 3D geometry changes of the fracture are followed in course of experiment, and can better be related to permeability changes. Our main results from dozen of experiments on limestone fracture in different mineral composition point at the rock texture on the evolution of reactive transport and possible feedbacks between chemical reactions and transport :
- the development of an altered layer in clayey limestone or marl acts as a diffusive barrier which leads to an exponential decrease of the chemical fluxes. See for instance our study published in Water Reasource Research: 
Noiriel et al. [2007]
- the development of an altered layer can lead to a neegative feedback between flow (e.g. permeability decrease) and porosity increase despite dissolution.
- the presence of low reactive minerals in fracture matrix makes difficult to predict fracture development to from initial fracture geometry. There is not necessary a positive feedback between areas of higher initial permeability and the development of preferential flowpaths. See for instance
Noiriel et al. [2007] and Noiriel et al. [2013]. These two studies were performed on the same rock type, but under two differents hydrodynamic conditions.

fractures fractures
Fracture void geometry evolution during dissolution in a marly limestone, associated to a decrease in hydraulic aperture and the development of a diffusive barrier in the growing altered layer, from Noiriel et al. [2007].


Investigation of pore-scale geometry evolution during CO2 injection

We have investigated pore-scale geometry evolution of rocks injected by CO2-rich fluid, in order to better understand the positive feeback between porosity and permeabilty increase. The reactivity of rock dissolution being directly proportional to the extend of the fluid-rock interface, we have followed the interface during 4D imaging experiments. Here, the geometric surface area of the fluid-rock interface was
calculated at different stages of a flow-through reactive experiment and compared with the changes of the solution chemistry. We were able to better link the huge increase of permeability to pore-scale porcesses, i.e., the displacement of fine mud particles, and the pore roughnesse decrease. More information in these two papers: Noiriel et al. [2004] and Noiriel et al. [2005]

Fluid-rock interface displacement
Fluid-rock interface displacement in a porous crinoïdal limestone during dissolution by acid fluid.




Some examples of 3D image processing


inclusion
Fluid-inclusion in fluorite (3-phase segmentation)


porous medium

porous medium 2x2mm
Packed column of calcite (
12×6 mm) spar and glass beads and 3D extract printing (×40)


tKmébi1
tKmébi1
Specimen of thecae amobae (labelling of the grains forming the theca)





 
 

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