14 de Diciembre a las 12:15h
Módulo D2 Planta Baja Aula CIHS
Is diffusion the same as mixing?
"Advection dispersion equation is the formulation most widely used to model solute transport in porous media. The dispersion term covers both: spreading of the plumes and mixing of the solute. In order to define the dispersion flux, concentration gradient is used. Because the two processes produce different effects, it is desired a distinction in the formulation. We propose a discussion about the very fundamental concepts of these processes (especially mixing and/or diffusion) which leads to a new formulation. A case study and results will be also presented."
a cargo de
a cargo de: BERTA GÓMEZ (UPC-CSIC)
Jueves 18 de enero a las 12:15 h
Departamento de Ingeniería Civil y Ambienta, Modulo D2-Aula CIHS, Planta Baja
Fracture failure is usually simulated by means of complex constitutive laws (i.e., plasticity, viscoelasticity, viscoplasticity, creep, etc.) which do not adequately represent the behavior of stiff, fragile rocks when their elastic limit is reached. The interest in the failure mechanism of this type of rocks has increased in the last years due to the progress of geological activities involving injection of fluids at depth (i.e., geological storage of CO2, enhanced geothermal energy or hydraulic fracturing operations). These applications usually provoke the creation of new fractures and/or the propagation of the pre-existing ones. Moreover, they may induce seismicity even after the shut-in, which is still not completely understood.
In the framework of the EU - FracRisk project, we want to improve the understanding of the failure process in fragile rocks and develop new methods to correctly simulate and predict the failure area in real fracking sites. In this regard, two methods to solve shear and tensile failure have been developed in the hydromechanical-application of the finite element framework Kratos. The first method is based on the analytical solution of Okada (1992), which is included in an iterative process to allow the simulation of the domino effect due to consecutive failure events that may take place. This is a straightforward method which avoids numerical issues but the underlying assumptions impose some restrictions to the modeling of real problems. In order to overcome these drawbacks, a novel numerical method has been developed. This method entails the construction of a Failure Matrix, which consists of the stress state variations in each fracture element due to a perturbation applied to each of them. Therefore, the superposition of the contribution to failure of each fracture element is considered. This Failure Matrix is specific for each model and it is built in a step previous to the beginning of the simulation.
The application of these methods allows us to correctly simulate failure in fragile rocks and to predict failure area and occurrence of seismicity during hydraulic fracturing operations.
a cargo de: Jordi Palau (CSIC-IDAEA)
Jueves 11 de Enero a las 12:15 h en Departamento de Ingeniería del Terreno, Aula CIHS, Planta Baja
Groundwater contamination by halogenated hydrocarbons like chlorinated ethanes is a major environmental problem and it has an adverse impact on water resources. In order to evaluate the fate and long-term impact of halogenated hydrocarbons in the aquifer, understanding of in situ contaminant transformation reactions is essential. Contaminant remediation schemes designed to enhance in situ degradation need to consider the reaction pathways by which contaminant transformation occurs and the rate of those reactions. However, the high susceptibility of chlorinated ethanes to be transformed via distinct degradation pathways complicates the assessment of their fate in the subsurface. This study investigates for the first time the use of a multi-element (C, Cl and H) isotope approach to identify the degradation pathways of 1,2-dichlorethane using five microbial cultures. In addition, this approach was tested in two contaminated field sites. The results demonstrated the potential of a multi-element isotope approach to identify 1,2-dichlorethane degradation pathways in groundwater, which opens further possibilities for pathway identification in future field studies.
SEMINARIO GRUPO DE HIDROLOGÍA SUBTERRANEA (UPC-CSIC)
Día: 30 de noviembre
Lugar: Aula del CIHS, Modulo D2, UPC
Autor: AHMAD ZAREI
Amirkabir University of Technology - Tehran Polytechnic.
Abstract: To attain the maximum production in hydrocarbon reservoirs, the use of enhanced oil recovery (EOR) methods is required. One EOR method consists in injecting gas, e.g., methane or CO2, in order to compensate the reservoir pressure decline and subsequently improving hydrocarbon production. This method causes stress changes in the injection region and may affect the geomechanical stability of the caprock. Caprocks of the studied carbonate reservoirs present complex structures and are highly layered, with alternating marl, salt, anhydride, shale and sandstone layers. Furthermore, information on geomechanical properties of these formations is scarce. These limitations and complexities highlight the challenges of performing comprehensive geomechanical studies to assess the short- and long-term integrity of the caprock during gas injection treatments. The overall objective of this research is to gain understanding of the geomechanical response of a fractured reservoir and its caprock to gas injection and to identify the regions of the caprock which are prone to undergo tensile or shear failure during the several cycles of production-injection along the reservoir lifecycle. To this end, thermo-hydro-mechanical coupled numerical modeling of gas injection in naturally fractured carbonate reservoirs, simulating the pressure buildup and temperature change in the fractures during the gas injection procedure will be performed
a cargo de
Investigador Científico del CSIC
Jueves 23 de Noviembre a las 12:15 h en Departamento de Ingeniería del Terreno, Aula CIHS, Planta Baja
Well-mixed flow-through experiments are used to study the dissolution kinetics of K-montmorillonite at 25 °C, acidic pH (2-4) and 0.01 M ionic strength. The variations of Si, Al and Mg over time result in high releases of Si and Mg and Al deficit and also in long periods of incongruent dissolution before reaching stoichiometric steady state. 1D RT simulations of the experimental data are performed to quantitatively interpret the evolution of the released cations and to elucidate the stoichiometry of the reaction.