Speaker: Consuelo Garcia Zavala

Date: Thursday 16th of November 2023, 1:15pm.

Abstract:

Lithium plays an essential role in global decarbonisation as lithium-based batteries are widely used in renewable energy and electric vehicles. The so-called “Lithium Triangle” extends over part of Chile, Argentina, and Bolivia, and holds around half of the world’s estimated reserves of lithium in the “salars”. Lithium extraction in this arid region raises challenges for the socio-ecological systems, which include fragile ecosystems and indigenous communities. Addressing these challenges requires companies to operationalise sustainability goals assuring continuous improvement of social and environmental performance, for which mining companies usually use socio-environmental management instruments. The question of whether these instruments are adequate to address the main social and environmental issues considering the particularities of this extractive activity taking place in unique geographic settings remains to be assessed. This project aims to understand the main socio-environmental issues associated with lithium extraction in the Lithium Triangle; and, through case studies, to assess whether existing socio-environmental assessment instruments are adequate for this activity and the complexity of this region.

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Category: Seminar

Speaker: Anne-Julie Tinet

Date: Thursday 5th of October 2023, 1:15pm.

Abstract:

Comprendre et modéliser le transport des contaminants est nécessaire pour évaluer la durée de vie et l’impact des sources de pollution et optimiser les stratégies de remédiation. Le transfert des contaminants de la phase NAPL (Non-Aqueous Phase Liquids) vers l'aquifère est un problème multi-échelle avec différents mécanismes de transport dans les phases et aux interfaces. Dans un 1^er temps, des simulations à l’échelle du pore sont réalisées avec COMSOL en considérant un NAPL multicomposant avec pour objectif l’étude du coefficient d’échange. En effet, les modèles à l'échelle macroscopique comprennent des équations de transport pour chaque phase qui sont couplées par un ou plusieurs coefficients d'échange de masse. Alors que ces coefficients, qui intègrent les impacts des différentes caractéristiques à l'échelle des pores (géométrie des pores, distribution des phases, vitesse d'écoulement), jouent un rôle clé dans le devenir de la source de pollution, ils sont généralement approximés, pour une saturation de phase donnée, par une valeur constante estimée à partir de corrélations empiriques. Dans un 2^e temps, des simulations macroscopiques de la dissolution de NAPL au niveau de la source de pollution représentée par un milieu hétérogène sont réalisées en faisant varier les conditions opératoires. Les courbes d’évolution des contaminants dissous prédites par la modélisation directe seront alors comparées aux résultats issus d’un modèle macroscopique 1D obtenu par changement d’échelle.

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Category: Seminar

Speaker: Enrico Scarpa

Date: Thursday 9th of November 2023, 1:15pm.

Abstract:

Starting from the 1990s, channel modeling research has been exploring how to replicate channel systems and examining the influence of modeling parameters on hydrocarbon recovery. Today, amid our strong commitment to ecological transitions, some of these investigations are shifting toward applications in CO2 storage and geothermal energy production. However, little attention has been directed towards understanding how facies elements within deposits affect the flow and heat transfer in geothermal energy systems. Often, small-scale heterogeneities in rock types are not represented in reservoir modeling due to the complexity of the geological models and the lack of data. This oversight leads to neglecting the reservoir connectivity of channel deposits. To tackle this absence, I aim to analyze how layers of shale within turbidite channels impact the performance of geothermal reservoirs. By using an appropriate stratigraphic grid setup, the volumes of the channels and the shale layers are preserved, allowing for the stochastic simulation of physical properties. Consequently, I will explore two geological scenarios: one with varied channels and another incorporating varied channels with shale layers. Using simple dynamic measurements, I will quantify the flow outcomes and compare these models. Results show that shale layers affect energy production, but the time for thermal breakthrough remains steady in both scenarios. This preliminary investigation prompts the inquiry of whether enhanced model realism is necessary for geothermal energy extraction.

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Category: Seminar

Speaker: Giusi Ruggiero

Date: Friday 29th of September 2023, 1:15pm.

Abstract:

In this talk I review some basic notions and mathematical tools in the  stochastic modeling of uncertainties and their quatification for large-scale computational models discussed during the 'Uncertainty Quantification Workshop' held at the Isaac Newton Institute of Mathematical Sciences at the University of Cambridge.

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Category: Seminar

Speaker: Jeremie Giraud

Date: Wednesday 8th of November 2023, 1:15pm.

Abstract:

This seminar will be divided into two main parts: In the first part, I will present an updated version of abstract S1214 that I presented in August at the IAMG 2023 Annual Meeting (Trondheim): I will introduce a trans-dimensional inversion technique for 3D gravity inversion, extending a multi-level set approach using signed-distance functions to model rock unit interfaces. It accommodates an unknown number of rock units through a birth-and-death process, allowing the addition or removal of units. It also allows the recovery of rock unit geometry and densities. In this presentation, I will show an application example in an undercover imaging scenario using data from the Boulia region (Queensland, Australia). Results suggest the presence of rock units concealed from surface geology and show the potential for the method to recover hidden geological features. In the second part, I will present some the non-scientific things I learned through my now-completed Marie Skłodowska-Curie Fellowship. The work that I will present was funded by the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 101032994.

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Category: Seminar

Speaker: Rachit Gautam

Date: Thursday 21st of September 2023, 1:15pm.

Abstract:

Toba caldera, the Earth's largest Quaternary volcanic complex, is located in north Sumatra at the forearc of the Sumatra subduction zone, along the Great Sumatran fault and the Investigator Fracture Zone. Its latest and largest known eruption to date, known as Youngest Toba eruption, occured 74,000 years ago and opened the central caldera hosting Lake Toba. In this study, I analysed earthquake waveform (passive seismic) data recorded by 42 three-component seismometers located across the caldera to measure and map total attenuation, scattering attenuation and absorption attenuation separately in 3D space. The coda normalisation method was used to measure total attenuation, S-wave peak delay measurements was used to quantify scattering attenuation and late time coda quality factor as marker for absorption attenuation. I was able to successfully perform total attenuation and peak-delay (scattering) analysis which produced high resolution and highly detailed 3D tomographic maps of my study area up to the depth of $\sim$15 km. The results of my study show that the crust beneath Toba caldera and the area south of it is highly heterogeneous. Multiple areas exhibiting high attenuation anomaly could be located at different depths beneath the southern part of Toba which I interpret as Magma bodies or the reservoirs containing magma derived materials (magmatic fluids, gases, etc.).

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Category: Seminar

Speaker: Massimiliano Schiavo

Date: Thursday 19th of October 2023, 1:15pm.

Abstract:

Groundwater pathways are permeable corridors where major subsurface discharges are conveyed. The ability to identify preferential groundwater pathways is crucial for a proper understanding of complex hydrogeological systems. These can be identified within a probabilistic framework upon two main ways of thinking, i.e. upon considering their delineation from an energy-based or a geologically-based perspective, both pursued from a geostatistical interpretation of available data. While both two methodologies rely upon geological data, like borehole and stratigraphic information, the former aims to identify the local aquifer bottom surface, and the latter considers only mostly permeable aquifer locations as suitable for being carved by a groundwater pathway. Both ways allow an in-depth understanding of the energetic and entropic behavior of such delineated pathways, consistent with other numerical, piezometric, and hydrogeological sources of information.

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Category: Seminar

Speaker: Juan Sebastian Osorno Bolivar

Date: Thursday 20th of July 2023, 1:15pm.

Abstract:

The restoration techniques that provide means for structural geologists to better understand the tectonic history of present-day geometries have been developed in a geomechanically consistent approach for more than 50 years. These usually involve linear elastic material properties, although the small deformation assumption does not hold in most case studies. Nonlinear elastic and plastic rheologies can model large deformations but they do not yield a time reversible scheme because of energy dissipation phenomena which cannot be recovered at geological timescales. Viscous deformations of geological layers described by Stokes equations have been shown to circumvent these obstacles. The goal of the present paper is to develop an inversion scheme for the effective viscosity of the geological materials at play, relying on the exploration of the admissible space based on an objective function related to the horizontality of the top surface. To perform the inversion, methods that have a strong performance solving ill-conditioned problems are considered: Covariance Matrix Adaptation Evolution Strategy (CMA-ES), Particle Swarm Optimization (PSO), Simulated Annealing, Random Search and Grid Search, all available in the GNIR library (Mazuyer et al., 2018). We apply the proposed approach to a synthetic 2D model of a faulted graben generated in the FAIStokes program (Schuh-Senlis et al., 2020).

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Category: Seminar

Speaker: Julien Herrero

Date: Thursday 12th of October 2023, 1:15pm.

Abstract:

This study presents a novel approach to handle structural uncertainties in the interpretation of stratigraphic structures using a transdimensional sampler, the reversible jump Markov chain Monte Carlo (RJMCMC) algorithm. Moving beyond conventional reservoir simulation models which use a fixed number of layers, the layering size is treated as variable. Hence, the number and position of model layers are unknowns to be determined by the inverse problem. The proposed method extends the application of one-dimensional RJMCMC by introducing a dip parameter, enabling the simulation of sedimentary wedges and erosional features around a well, which is not typically accounted for in standard layer-cake models used for instance in well test interpretation. To keep the model dimension low, a two-dimensional, piecewise constant permeability field is determined for each layering configuration. This inverse method, tested on a synthetic well log, facilitates robust interpretations of geological reservoir geometries and could improve the prediction of permeability spatial distribution in sedimentary settings. Demonstrating successful recovery of target models, the study opens interesting perspectives both for near-well subsurface models and full field reservoir models, and identifies the need for future work on allowing interface intersections to simulate more complex stratigraphic structures.

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Category: Seminar