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UPC: C/ Jordi Girona 31, (08034 - Barcelona) - IDAEA: C/ Jordi Girona 18-26, (08034 - Barcelona)

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How to quantify mixing and upscale reaction in heterogeneous porous media

Webinar cycle in Hydrogeology and geochemistry

EACH THURSDAY (free of charge)

live in: https://meet.google.com/snb-qdkn-eex   

HYDROGEOLOGY GROUP

(Assoc

iated Unit CSIC-UPC, Barcelona)

Next webinar: Thursday, 27 May, 2021

Starting time: 12:15 (Central European Time)

Duration: 1h

 

This week's guest speaker: Alexandre Puyguiraud


Abstract:
We upscale reactive mixing using effective dispersion coefficients to
capture the combined effect of pore-scale heterogeneity and molecular
diffusion on the evolution of the mixing interface between two initially
segregated dissolved species. These effective dispersion coefficients
are defined as the average spatial variance of the solute plume that
evolves from a pointlike injection (the transport Green function).
We numerically investigate the effective longitudinal dispersion
coefficients in two porous media of different structure heterogeneity
and through different Péclet number regimes for each medium. We find
that, as distance traveled increases (or time spent), the solute
experiences the pore-scale velocity field heterogeneity due to advection
and transverse diffusion, resulting in an evolution of the dispersion
coefficients. They evolve from the value of molecular diffusion at early
time, then undergo an advection dominated regime, to finally reach the
value of hydrodynamic dispersion at late times. Thus, at times smaller
than the diffusion time over a characteristic pore length, the effective
dispersion coefficients can be significantly smaller than the
hydrodynamic dispersion coefficients. Therefore, mismatches between
pore-scale reaction data from experiment or simulations and Darcy scale
predictions based on temporally constant hydrodynamic dispersion can be
explained through these differences. We use the effective dispersion
coefficients to approximate the transport Green function and to quantify
the incomplete mixing occurring at the pore-scale. We evaluate the
evolution of two initially segregated species via this methodology. The
dispersive lamella approach accurately predicts the evolution of the
product mass of an instantaneous bimolecular reaction obtained from
direct numerical simulations. These results shed some new light on
pore-scale mixing, the notion of incomplete mixing, and its predictionand upscaling in terms of an effective mixing model.

Link presentation

 

How could the largest earthquake in any underground gas storage be induced at Castor?

Webinar cycle in Hydrogeology and geochemistry

EACH THURSDAY (free of charge)

live in: https://meet.google.com/snb-qdkn-eex   

HYDROGEOLOGY GROUP

(Associated Unit CSIC-UPC, Barcelona)

Next webinar: Thursday, 10 Juny, 2021

Starting time: 12:15 (Central European Time)

Duration: 1h

 

This week's guest speaker: Victor Vilarrasa, Researcher CSIC

 

Abstract

The Underground Gas Storage (UGS) project of Castor, Spain, caused the three largest earthquakes (M4.08, M4.01 and M3.97) ever induced by any of the more than 640 UGS facilities all around the world. Injection of cushion gas, which lasted for 15 days, induced hundreds of seismic events, with the largest earthquakes being felt by the local population despite the platform was located some 20 km off the coast. The project was finally cancelled, implying an investment compensation to the operating company that may cost up to 4.73 billion euros to Spanish citizens. The largest magnitude earthquakes at Castor have the following interesting features: 1) they occurred 20 days after the stop of injection, 2) they nucleated between 4 to 10 km, much deeper than the injection depth, i.e., 1.7 km, and 3) they are the largest ever induced in a UGS. We have proposed a plausible combination of triggering mechanisms that explains these features of the induced seismicity (Vilarrasa et al., 2021). First, gas injection reactivated, through pore pressure buildup and buoyancy, the critically stressed Amposta fault, which bounded the storage formation. The Amposta fault crept even after the stop of injection because of the permanent effect of buoyancy caused by the injected gas. The progressive accumulation of aseismic slip of the Amposta fault eventually reactivated a critically stressed unmapped deep fault through shear slip stress transfer. Once this deep fault was reactivated, the sequence of earthquakes was induced by shear slip stress transfer, with transient deformation-induced pore pressure changes likely controlling the delay between earthquakes. The high risk of inducing seismicity at Castor would have been identified prior to gas injection by analyzing fault stability.

 

You can see the seminar in our page www.h2ogeo.upc.edu

Title: Numerical Analysis of the Effect of Heterogeneity on Enhanced Dissolution of CO2 Due to Gravity Driven Convection

Webinar cycle in Hydrogeology and geochemistry

EACH THURSDAY (free of charge)

live in: https://meet.google.com/snb-qdkn-eex   

 HYDROGEOLOGY GROUP

(Associated Unit CSIC-UPC, Barcelona)

 Next webinar: Thursday, 3 Juny, 2021

Starting time: 12:15 (Central European Time)

Duration: 1h

 

This week's guest speaker: Yufei Wang



Abstract:
Solution trapping of CO2 in brine plays an important role in long-term
geological sequestration of CO2. The dissolution of overlying gaseous
CO2 will increase the density of brine, causing gravity-driven
convection (GDC) in brine phase and thus significantly increasing the
solution trapping efficiency. To date, we do not have an efficient
formula to predict the GDC-induced dissolution rate in heterogeneous
fields. The challenge is to find the most related character of the
field, from which we can efficiently predict the dissolution rate. Here,
with aid of systematically numerical simulations, we study how GDC is
affected by the effect of permeability heterogeneity including layered
formation, and obtain two physically sound empirical formulas to predict
the dissolution rate based on the field characters.
Analysis of the results shows that (1) the GDC-induced dissolution rate
(F) is proportional to the vertical flow connectivity, in which flow
connectivity is characterized by the dimensionless effective
permeability; (2) F is proportional to the vertical finger tip velocity,
which is characterized by the dimensionless maximum cross-sectional mean
absolute vertical velocity; (3) in anisotropic formation, the
dissolution rate is also proportional to the square root of the ratio of
vertical to horizontal flow connectivity. All the simulations are
conducted on length and time scales much smaller than those in the
regional scale. The results from these small-scale simulations can be
employed as a source term for the regional-scale simulations, where the
coarse grid size may not precisely capture the GDC.

 

Link presentation

Title: Numerical simulation of coupled processes in a single fracture employing a continuum approach

Webinar cycle in Hydrogeology and geochemistry

EACH THURSDAY (free of charge)

live in: https://meet.google.com/snb-qdkn-eex   

HYDROGEOLOGY GROUP

(Associated Unit CSIC-UPC, Barcelona)

Next webinar: Thursday, 20 May, 2021

Starting time: 12:15 (Central European Time)

Duration: 1h

 

This week's guest speaker: Iman Vaezi

Abstract

Fractures control fluid flow and the coupled geomechanical response of geological media in many geo-engineering applications. For instance, fractures dominate fluid flow and deformation in enhanced geothermal systems, underground radioactive waste repositories and CO2 storage. Coupled thermo-hydro-mechanical processes in rock masses are a result of perturbations in the pore pressure, as in fluid injection and/or production, and/or temperature, as in cold fluid injection and disposal of radioactive waste. For example, fractures open as a result of pore pressure increase, which simultaneously increases permeability and reduces overpressure.

Geo-engineering and geo-energy applications involve large portion of rock mass that include several fractures. Numerical computations of coupled processes occurring in rock masses while considering a large number of fractures pose several challenges. I will present a study in which we firstly focus on a simple problem to fully understand the hydro-mechanical behavior of a single fracture subjected to a constant injection flow rate. We use the FEM software CODE_BRIGHT, which solves the thermo-hydro-mechanical governing equations in a fully coupled way. Since standard FEM can solve equations in continuum media, we investigate the behavior of a single fracture by analyzing the hydro-mechanical parameters that control the fracture response in continuum fashion. However, simulating fractures with the real aperture is not simply feasible, hence, we search the equivalent properties of thicker fractures that are more feasible to be discretized in large-scale models with several fractures.

 

Natural Attenuation of heavy metals via secondary hydrozincite precipitation in an abandoned Pb-Zn mine in the Aran Valley, Spain

Webinar cycle in Hydrogeology and geochemistry

EACH THURSDAY (free of charge)

live in: https://meet.google.com/snb-qdkn-eex   

 

HYDROGEOLOGY GROUP

(Associated Unit CSIC-UPC, Barcelona)

 

Next webinar: Thursday, 13 May, 2021

Starting time: 12:15 (Central European Time)

Duration: 1h

 

 

 

This week’s Guest Speaker : Max G. Giannetta (IDAEA, CSIC)


Títle:
Natural Attenuation of heavy metals via secondary hydrozincite
precipitation in an abandoned Pb-Zn mine in the Aran Valley, Spain

Abstract:
The Aran Valley has a long history of mining activities (~1740-1950).
Many of the abandoned mining sites such as tunnels and processing
facilities have not been properly reclaimed. Further, these sites can
often be characterized by elevated levels of heavy metals due to the
dissolution of left-over ore material. This in turn, may pose an
environmental risk to the adjacent ecosystem.
The Victoria Mine in the Aran Valley was active until 1950. The
underground mine targeted sphalerite (ZnS) while limestone is present in
abundance. Today the relict tunnels and shafts are exposed to air and
flowing water provoking oxidative dissolution and contemporary microbial
activity alongside secondary precipitation of minerals. Surface waters
within and below the mine would be considered dangerous if consumed by
humans due to elevated levels of Cd (up to ~28 ppb). The source of
dissolved Cd is almost certainly the solid ZnS, which is abnormally rich
in Cd (upwards of ~5000 ppm).
Biomineralization of hydrozincite has been demonstrated as a naturally
occurring process in the presents of abundant dissolved zinc, carbonate,
and sunlight. However, biomineralization of hydrozincite without
sunlight has yet to be discovered. Further, this mineral can act as a
sink for Cd, therefore understanding the controls of its formation can
be useful for predicting heavy metal availability.
The outflow water of the Victoria Mine poses an environmental risk due
to the elevated concentrations of Cd (27.5 ± 6.5 ppb), however, these
concentrations would be higher if hydrozincite was not forming and
acting as a sink for the cadmium. Biomineralization of hydrozincite by
microorganisms, though no proven at present, could be possible because
(1) microorganisms consistent with biomineralization of calcite found in
the DNA analysis and (2) the variable morphologies of hydrozincite which indicate there is more than one avenue for precipitation.

 

Link presentation

Lagrangian methods for modelling reactive transport in heterogeneous aquifers

Webinar cycle in Hydrogeology and geochemistry

EACH THURSDAY (free of charge)

live in: https://meet.google.com/snb-qdkn-eex   

HYDROGEOLOGY GROUP

(Associated Unit CSIC-UPC, Barcelona)

Next webinar: Thursday, 6 May, 2021

Starting time: 12:15 (Central European Time)

Duration: 1h

  This week’s Guest Speaker: Rodrigo Perez, ITN phD Student.

 

Title of the talk: Lagrangian methods for modelling reactive transport in
heterogeneous aquifers

 

Abstract:

Particle or Lagrangian methods have shown several advantages
when considered for the resolution of solute transport problems in
heterogeneous domains. Specifically, their inherent capacity for
capturing high complexity spatial features and the absence of artificial
diffusion observed in grid-based models, stand as some of their more
attractive qualities which are highly relevant when considered for
reactive transport processes. This seminar discuss two Lagrangian
formulations and their potential as modelling approach specifically in
the context of reactive transport modelling. Discussed methods are
Smoothed Particle Hydrodynamics (SPH) and Random Walk Particle Tracking
(RWPT). Theoretical and practical aspects related to software
implementation will be discussed.

 

Link presentation

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