Patricia Gauzellino - Academia.edu (original) (raw)

Papers by Patricia Gauzellino

EGU General Assembly Conference Abstracts, Apr 1, 2012

ABSTRACT In this work it is numerically shown that methane hydrate-bearing sediments located belo... more ABSTRACT In this work it is numerically shown that methane hydrate-bearing sediments located below permafrost can be detected using electric currents as sources; the seismic signals originated where the conversion from electromagnetic to seismic energy takes place could be measured by means of geophones or accelerometers located on the surface and/or in wells. In order to appropiately model seismic wave propagation both in permafrost and gas-hydrate bearing environments, an extended Biot-type formulation taking into account the different mechanical properties of the solid matrix, ice and gas hydrates is included in Pride's electroseismic equations. The latter are considered in a two dimensional Earth, along with two different electromagnetic sources, namely an infinitely long solenoid giving rise to the PSVTM mode and an infinite current line giving rise to the SHTE mode, and complemented by absorbing boundary conditions for both the electromagnetic and poroviscoelastic portions of the model equations. The numerical solutions are obtained by means of finite elements algorithms devised to be efficiently run on parallel computers. An example consisting of a gas hydrate-bearing slab located underneath the permafrost base is presented, the obtained results indicate that the seismic response is sensitive to the methane hydrate concentration.

64th EAGE Conference & Exhibition, 2002

Mecánica Computacional, 2005

Seismic methods of subsurface exploration are based on mechanical wave propagation and the numeri... more Seismic methods of subsurface exploration are based on mechanical wave propagation and the numerical modeling of these phenomena is a worthy tool that can be applied as a complement. Since small regions of Earth’s crust are studied, it is necessary to consider absorbing boundary conditions for solving the wave equations efficiently. Therefore, this work presents a derivation of low-order absorbing boundary conditions at the artificial boundaries of the computational domain with the purpose of minimizing spurious reflections. Laboring on a surface S, which separates disturbed and undisturbed regions of the domain, the equations for the absorbing boundary conditons are derived from kinematic conditions, considering continuity of the displacements across S and dynamic conditions, using momentum equations of the wave fronts arriving normally to S and expressions for the strain energy density along S. The arguments to obtain non-reflecting artificial boundaries are carried out for the more ge...

Latin American Applied Research - An international journal, 2021

A pandemic caused by a new corona virus has spread worldwide, affecting Argentina. We implement a... more A pandemic caused by a new corona virus has spread worldwide, affecting Argentina. We implement an SEIR model to analyze the disease evolution in Buenos Aires and neighboring cities.The model parameters are calibrated using the number of casualties officially reported. Since infinite solutions honor the data, we show different cases. In all of them the reproduction ratio R0 decreasesafter early lockdown, but then raises, probably due to an increase in the community circulation of the virus. Therefore it is mandatory to reverse this growing trend in R0 by applying control strategiesto avoid a high number of infectious and dead individuals. The model provides an effective procedure to estimate epidemic parameters (fatality rate, transmission probability, infection and incubationperiods) and monitor control measures during the epidemic evolution.

En este trabajo se presenta la manera en la cual, desde la ensenanza de los metodos numericos, se... more En este trabajo se presenta la manera en la cual, desde la ensenanza de los metodos numericos, se busca vincular los contenidos especificos de la matematica aplicada con la practica profesional futura de los alumnos. La ubicacion de la asignatura en el plan de estudios de las distintas ingenierias, hace que los estudiantes que toman el curso no tengan aun conocimientos especificos de sus especialidades y por ende no se hayan enfrentado todavia a la necesidad de dar respuestas a problemas de dificil resolucion analitica; mucho menos a la resolucion de casos practicos, donde la informacion no se presenta de la forma a la que estan habituados en esta etapa de su formacion. La catedra propone un laboratorio integrador, presentando un problema que requiere una serie de resultados encadenados, que deben ser resueltos mediante distintos procedimientos numericos, desarrollando el correspondiente codigo Octave/MatLab y escribiendo un informe. Por lo tanto, es posible vincular la aplicacion d...

En este trabajo se trata de reducir el tiempo de computo en un programa de optimizacion no lineal... more En este trabajo se trata de reducir el tiempo de computo en un programa de optimizacion no lineal. Se utiliza el algoritmo FAIPA (Feasible Arc Interior Point Algorithm), de punto interior. Partiendo de un punto situado en la region admisible va moviendose siempre dentro de esa region. El calculo de la direccion de busqueda se hace a partir de tres direcciones basicas. Cada una de estas resulta de resolver un sistema de ecuaciones algebraicas lineales. Los tres sistemas tienen la misma matriz de coeficientes, diferenciandose solo en el vector de terminos independientes. El tamano de estos sistemas es igual a la cantidad de variables de diseno mas el numero de restricciones. Se propone un resolvedor de tipo LDU (es decir a traves de una factorizacion de la matriz, con L matriz triangular inferior; D matriz diagonal y U matriz triangular superior). Como es sabido la factorizacion insume una cantidad de operaciones del orden del cubo del tamano de la matriz, y las sustituciones hacia ad...

Journal of Computer Science and Technology, 2013

This paper presents a collection of finite element procedures to model seismic wave propagation a... more This paper presents a collection of finite element procedures to model seismic wave propagation at the macroscale taking into account the effects caused by heterogeneities occuring at the mesoscale. For this purpose we first apply a set of compressibility and shear experiments to representative samples of the heterogeneous fluid saturated material. In turn these experiments yield the effective coefficients of an anisotropic macroscopic medium employed for numerical simulations at the macroscale. Numerical experiments illustrate the implementation of the proposed methodology to model wave propagation at the macroscale in a patchy brine-CO2 saturated porous medium containing a dense set of parallel fractures.

The conversion of energy between seismic and electromagnetic wave fields involves relative movemen... more The conversion of energy between seismic and electromagnetic wave fields involves relative movement of ions at the rock-fluid contact surfaces in the pore space, described by Biot’s equations of motion in poroviscoelastic media coupled with Maxwell’s equations. The numerical simulation of seismoelectrograms allows to analyze full-waveform coupled seismoelectromagnetic wave propagation in fluid-saturated porous media. It is possible to observe two different responses: the coseismic response with the same waveform as a seismic wave and the interface response that occurs when a seismic wave encounters a contrast in electrical or mechanical material properties. The proposed algorithm calculates the electromagnetic field from seismic displacements, particularly fluid displacements, using the finite element method employing a parallelizable non-overlapping domain decomposition technique, which is required due to the high computational cost of the problem. The seismoelectric method allows the po...

The present technologies for the acquisition and processing of seismic data such as cross-dipole ... more The present technologies for the acquisition and processing of seismic data such as cross-dipole sonic profiles, VSPs walkaround and walkaway, or seismic multicomponent (3C) allow to measure wave propagation in different directions. This way, by making an analysis of velocity, attenuation, AVO or AVAz, a mechanical characterization of the medium anisotropy is obtained. The following work presents an analysis of wave propagation in Vaca Muerta. The different seismic behaviours, depending on the elastic symmetry and the reflection coefficient of the systems (Quintuco-Vaca Muerta and Vaca MuertaTordillo), are studied. Following this objective, a new tool based on the Finite Element Method (FEM) was developed, which allows the simulation of a full wave propagation (wave conversion modes). This simulation process generates synthetic seismograms, which are sensitive to the medium anisotropy. It also allows to build velocity models with higher accuracy for the calibration of several kinds ...

La presencia de fracturas y campos de esfuerzos direccionales en el subsuelo pueden determinarse ... more La presencia de fracturas y campos de esfuerzos direccionales en el subsuelo pueden determinarse a traves de la anisotropia de velocidades que se observa en la propagacion de las ondas sismicas. Estimar estos parametros es de importancia tanto en la prospeccion de hidrocarburos como en la mineria. Las variaciones de amplitud en la respuesta sismica con respecto a angulos verticales o polares (AVO, Amplitude Versus Offset) y angulos horizontales o acimutales (AVAz, Amplitude Versus Azimuth) son los atributos que brindan informacion sobre el estado de fracturamiento y tensiones del medio. El trabajo propuesto consiste de dos partes principales. En la primera parte se obtienen los CMP-gathers sinteticos con Abaqus-CAE para una arenisca fracturada y saturada con gas, que se encuentra confinada entre dos lutitas (shale); exponiendo una metodologia de modelado que permite superar limitaciones de hardware. En la segunda parte, se realiza el procesamiento de los datos aplicando filtros y corr...

A major cause of the attenuation levels observed in seismic data from sedimentary regions is the ... more A major cause of the attenuation levels observed in seismic data from sedimentary regions is the mesoscopic loss mechanism, caused by heterogeneities in the rock and fluid properties greater than the pore size but much smaller than the wavelengths of the fast compressional and shear waves. The main objective of this paper is to apply a numerical upscaling method to determine the plane wave complex modulus of a viscoelastic solid long-wave equivalent to a fluid saturated poroelastic (Biot’s medium) with mesoscopic-scale heterogeneities in the form of brine-CO2 patches. This is achieved by applying time-harmonic compressibility tests at a selected set of frequencies to a representative sample of bulk material. These tests are modeled as boundary value problems stated in the space-frequency domain. This numerical upscaling approach was applied using data from the CO2 sequestration Sleipner-field case. A numerical flow simulator to represent the CO2 injection and storage was combined wi...

We investigate the numerical dispersive properties of nonconforming nite element methods to solve... more We investigate the numerical dispersive properties of nonconforming nite element methods to solve the two and three dimensional elastodynamic equations. The study is performed by deriving and analysing the dispersion relations and by evaluating the derived quantities, such as the dimension-less phase and group velocities. Also the phase di erence between exact and numerical solutions is investigated. The method studied, which yields a linear spatial approximation, demonstrates to be less dispersive than conforming bilinear nite element methods yielding the same spatial degree of approximation in the two cases shown herein.

Computational Geosciences, 2021

We present a novel numerical upscaling technique for modeling the wave response of gas-hydrate be... more We present a novel numerical upscaling technique for modeling the wave response of gas-hydrate bearing sediments composed of a rock frame, gas-hydrate and water, where the hydrate consists of ice-like lattice of water molecules with methane trapped inside. These sediments are highly heterogeneous at mesoscopic scales, much smaller than the wavelength but much larger than the pore size, inducing substantial seismic wave attenuation and dispersion due to mode conversions. The proposed numerical upscaling procedure simulates the wave-induced fluid-flow loss mechanism by computing an average effective viscoelastic medium having the same behavior of the original sediment. The method determines the complex stiffness coefficients associated with the viscoelastic medium by solving numerically boundary value problems formulated in the space-frequency domain, representing compressibility and shear experiments. The procedure is applied to composite media with regions of different amounts of hydrate with patchy or periodic-layer distributions, which define an anisotropic effective viscoelastic medium, respectively. The examples demonstrate that variations in hydrate content induce strong attenuation and dispersion effects on seismic waves due to the mesoscopic loss mechanism.

Infosys Science Foundation Series, 2021

Numerical Simulation in Applied Geophysics, 2016

Storage of carbon dioxide (CO2) in deep saline aquifers and aging oil reservoirs is a valid alter... more Storage of carbon dioxide (CO2) in deep saline aquifers and aging oil reservoirs is a valid alternative approach for reducing the amount of greenhouse gases in the atmosphere. This procedure can be modeled by the combined use of multi-phase fluid flow and wave propagation. The flow simulator is used to model the CO2 injection, and seismic monitoring is applied to determine the spatiotemporal distribution of CO2 after several years of injection. The simultaneous flow of brine and CO2 is modeled with the Black-Oil formulation for two-phase flow in porous media, while wave propagation is formulated using an isotropic viscoelastic model. The CO2 saturation and pressure data computed with the flow simulator is used in a petrophysical model to determine the complex bulk and shear moduli of the formation. Wave propagation is performed using a finite element domain decomposition procedure. The simulation is used to model CO2 injection and flow and compute time-lapse seismograms corresponding to the Utsira aquifer at Sleipner field with the objective of identifying the spatio-temporal distribution of CO2 after injection.

Numerical Simulation in Applied Geophysics, 2016

Fast compressional or shear waves travelling through a fluid-saturated porous material (a Biot me... more Fast compressional or shear waves travelling through a fluid-saturated porous material (a Biot medium) containing heterogeneities on the order of centimeters (mesoscopic scale) suffer attenuation and dispersion observed in seismic data. The mesoscopic loss effect occurs because different regions of the medium may undergo different strains and fluid pressures. This in turn induces fluid flow and Biot slow waves causing energy losses and velocity dispersion. Numerical modeling of wave propagation using Biot's equations of motion takes into account this phenomenon but is computationally very expensive. In the context of Numerical Rock Physics, this chapter presents compressibility and shear time-harmonic experiments to determine an equivalent viscoelastic medium having in the average the same attenuation and velocity dispersion than the original highly heterogeneous Biot medium. Each experiment is associated with a boundary-value problem that is solved using the finite element method.

EGU General Assembly Conference Abstracts, Apr 1, 2012

ABSTRACT In this work it is numerically shown that methane hydrate-bearing sediments located belo... more ABSTRACT In this work it is numerically shown that methane hydrate-bearing sediments located below permafrost can be detected using electric currents as sources; the seismic signals originated where the conversion from electromagnetic to seismic energy takes place could be measured by means of geophones or accelerometers located on the surface and/or in wells. In order to appropiately model seismic wave propagation both in permafrost and gas-hydrate bearing environments, an extended Biot-type formulation taking into account the different mechanical properties of the solid matrix, ice and gas hydrates is included in Pride's electroseismic equations. The latter are considered in a two dimensional Earth, along with two different electromagnetic sources, namely an infinitely long solenoid giving rise to the PSVTM mode and an infinite current line giving rise to the SHTE mode, and complemented by absorbing boundary conditions for both the electromagnetic and poroviscoelastic portions of the model equations. The numerical solutions are obtained by means of finite elements algorithms devised to be efficiently run on parallel computers. An example consisting of a gas hydrate-bearing slab located underneath the permafrost base is presented, the obtained results indicate that the seismic response is sensitive to the methane hydrate concentration.

64th EAGE Conference & Exhibition, 2002

Mecánica Computacional, 2005

Seismic methods of subsurface exploration are based on mechanical wave propagation and the numeri... more Seismic methods of subsurface exploration are based on mechanical wave propagation and the numerical modeling of these phenomena is a worthy tool that can be applied as a complement. Since small regions of Earth’s crust are studied, it is necessary to consider absorbing boundary conditions for solving the wave equations efficiently. Therefore, this work presents a derivation of low-order absorbing boundary conditions at the artificial boundaries of the computational domain with the purpose of minimizing spurious reflections. Laboring on a surface S, which separates disturbed and undisturbed regions of the domain, the equations for the absorbing boundary conditons are derived from kinematic conditions, considering continuity of the displacements across S and dynamic conditions, using momentum equations of the wave fronts arriving normally to S and expressions for the strain energy density along S. The arguments to obtain non-reflecting artificial boundaries are carried out for the more ge...

Latin American Applied Research - An international journal, 2021

A pandemic caused by a new corona virus has spread worldwide, affecting Argentina. We implement a... more A pandemic caused by a new corona virus has spread worldwide, affecting Argentina. We implement an SEIR model to analyze the disease evolution in Buenos Aires and neighboring cities.The model parameters are calibrated using the number of casualties officially reported. Since infinite solutions honor the data, we show different cases. In all of them the reproduction ratio R0 decreasesafter early lockdown, but then raises, probably due to an increase in the community circulation of the virus. Therefore it is mandatory to reverse this growing trend in R0 by applying control strategiesto avoid a high number of infectious and dead individuals. The model provides an effective procedure to estimate epidemic parameters (fatality rate, transmission probability, infection and incubationperiods) and monitor control measures during the epidemic evolution.

En este trabajo se presenta la manera en la cual, desde la ensenanza de los metodos numericos, se... more En este trabajo se presenta la manera en la cual, desde la ensenanza de los metodos numericos, se busca vincular los contenidos especificos de la matematica aplicada con la practica profesional futura de los alumnos. La ubicacion de la asignatura en el plan de estudios de las distintas ingenierias, hace que los estudiantes que toman el curso no tengan aun conocimientos especificos de sus especialidades y por ende no se hayan enfrentado todavia a la necesidad de dar respuestas a problemas de dificil resolucion analitica; mucho menos a la resolucion de casos practicos, donde la informacion no se presenta de la forma a la que estan habituados en esta etapa de su formacion. La catedra propone un laboratorio integrador, presentando un problema que requiere una serie de resultados encadenados, que deben ser resueltos mediante distintos procedimientos numericos, desarrollando el correspondiente codigo Octave/MatLab y escribiendo un informe. Por lo tanto, es posible vincular la aplicacion d...

En este trabajo se trata de reducir el tiempo de computo en un programa de optimizacion no lineal... more En este trabajo se trata de reducir el tiempo de computo en un programa de optimizacion no lineal. Se utiliza el algoritmo FAIPA (Feasible Arc Interior Point Algorithm), de punto interior. Partiendo de un punto situado en la region admisible va moviendose siempre dentro de esa region. El calculo de la direccion de busqueda se hace a partir de tres direcciones basicas. Cada una de estas resulta de resolver un sistema de ecuaciones algebraicas lineales. Los tres sistemas tienen la misma matriz de coeficientes, diferenciandose solo en el vector de terminos independientes. El tamano de estos sistemas es igual a la cantidad de variables de diseno mas el numero de restricciones. Se propone un resolvedor de tipo LDU (es decir a traves de una factorizacion de la matriz, con L matriz triangular inferior; D matriz diagonal y U matriz triangular superior). Como es sabido la factorizacion insume una cantidad de operaciones del orden del cubo del tamano de la matriz, y las sustituciones hacia ad...

Journal of Computer Science and Technology, 2013

This paper presents a collection of finite element procedures to model seismic wave propagation a... more This paper presents a collection of finite element procedures to model seismic wave propagation at the macroscale taking into account the effects caused by heterogeneities occuring at the mesoscale. For this purpose we first apply a set of compressibility and shear experiments to representative samples of the heterogeneous fluid saturated material. In turn these experiments yield the effective coefficients of an anisotropic macroscopic medium employed for numerical simulations at the macroscale. Numerical experiments illustrate the implementation of the proposed methodology to model wave propagation at the macroscale in a patchy brine-CO2 saturated porous medium containing a dense set of parallel fractures.

The conversion of energy between seismic and electromagnetic wave fields involves relative movemen... more The conversion of energy between seismic and electromagnetic wave fields involves relative movement of ions at the rock-fluid contact surfaces in the pore space, described by Biot’s equations of motion in poroviscoelastic media coupled with Maxwell’s equations. The numerical simulation of seismoelectrograms allows to analyze full-waveform coupled seismoelectromagnetic wave propagation in fluid-saturated porous media. It is possible to observe two different responses: the coseismic response with the same waveform as a seismic wave and the interface response that occurs when a seismic wave encounters a contrast in electrical or mechanical material properties. The proposed algorithm calculates the electromagnetic field from seismic displacements, particularly fluid displacements, using the finite element method employing a parallelizable non-overlapping domain decomposition technique, which is required due to the high computational cost of the problem. The seismoelectric method allows the po...

The present technologies for the acquisition and processing of seismic data such as cross-dipole ... more The present technologies for the acquisition and processing of seismic data such as cross-dipole sonic profiles, VSPs walkaround and walkaway, or seismic multicomponent (3C) allow to measure wave propagation in different directions. This way, by making an analysis of velocity, attenuation, AVO or AVAz, a mechanical characterization of the medium anisotropy is obtained. The following work presents an analysis of wave propagation in Vaca Muerta. The different seismic behaviours, depending on the elastic symmetry and the reflection coefficient of the systems (Quintuco-Vaca Muerta and Vaca MuertaTordillo), are studied. Following this objective, a new tool based on the Finite Element Method (FEM) was developed, which allows the simulation of a full wave propagation (wave conversion modes). This simulation process generates synthetic seismograms, which are sensitive to the medium anisotropy. It also allows to build velocity models with higher accuracy for the calibration of several kinds ...

La presencia de fracturas y campos de esfuerzos direccionales en el subsuelo pueden determinarse ... more La presencia de fracturas y campos de esfuerzos direccionales en el subsuelo pueden determinarse a traves de la anisotropia de velocidades que se observa en la propagacion de las ondas sismicas. Estimar estos parametros es de importancia tanto en la prospeccion de hidrocarburos como en la mineria. Las variaciones de amplitud en la respuesta sismica con respecto a angulos verticales o polares (AVO, Amplitude Versus Offset) y angulos horizontales o acimutales (AVAz, Amplitude Versus Azimuth) son los atributos que brindan informacion sobre el estado de fracturamiento y tensiones del medio. El trabajo propuesto consiste de dos partes principales. En la primera parte se obtienen los CMP-gathers sinteticos con Abaqus-CAE para una arenisca fracturada y saturada con gas, que se encuentra confinada entre dos lutitas (shale); exponiendo una metodologia de modelado que permite superar limitaciones de hardware. En la segunda parte, se realiza el procesamiento de los datos aplicando filtros y corr...

A major cause of the attenuation levels observed in seismic data from sedimentary regions is the ... more A major cause of the attenuation levels observed in seismic data from sedimentary regions is the mesoscopic loss mechanism, caused by heterogeneities in the rock and fluid properties greater than the pore size but much smaller than the wavelengths of the fast compressional and shear waves. The main objective of this paper is to apply a numerical upscaling method to determine the plane wave complex modulus of a viscoelastic solid long-wave equivalent to a fluid saturated poroelastic (Biot’s medium) with mesoscopic-scale heterogeneities in the form of brine-CO2 patches. This is achieved by applying time-harmonic compressibility tests at a selected set of frequencies to a representative sample of bulk material. These tests are modeled as boundary value problems stated in the space-frequency domain. This numerical upscaling approach was applied using data from the CO2 sequestration Sleipner-field case. A numerical flow simulator to represent the CO2 injection and storage was combined wi...

We investigate the numerical dispersive properties of nonconforming nite element methods to solve... more We investigate the numerical dispersive properties of nonconforming nite element methods to solve the two and three dimensional elastodynamic equations. The study is performed by deriving and analysing the dispersion relations and by evaluating the derived quantities, such as the dimension-less phase and group velocities. Also the phase di erence between exact and numerical solutions is investigated. The method studied, which yields a linear spatial approximation, demonstrates to be less dispersive than conforming bilinear nite element methods yielding the same spatial degree of approximation in the two cases shown herein.

Computational Geosciences, 2021

We present a novel numerical upscaling technique for modeling the wave response of gas-hydrate be... more We present a novel numerical upscaling technique for modeling the wave response of gas-hydrate bearing sediments composed of a rock frame, gas-hydrate and water, where the hydrate consists of ice-like lattice of water molecules with methane trapped inside. These sediments are highly heterogeneous at mesoscopic scales, much smaller than the wavelength but much larger than the pore size, inducing substantial seismic wave attenuation and dispersion due to mode conversions. The proposed numerical upscaling procedure simulates the wave-induced fluid-flow loss mechanism by computing an average effective viscoelastic medium having the same behavior of the original sediment. The method determines the complex stiffness coefficients associated with the viscoelastic medium by solving numerically boundary value problems formulated in the space-frequency domain, representing compressibility and shear experiments. The procedure is applied to composite media with regions of different amounts of hydrate with patchy or periodic-layer distributions, which define an anisotropic effective viscoelastic medium, respectively. The examples demonstrate that variations in hydrate content induce strong attenuation and dispersion effects on seismic waves due to the mesoscopic loss mechanism.

Infosys Science Foundation Series, 2021

Numerical Simulation in Applied Geophysics, 2016

Storage of carbon dioxide (CO2) in deep saline aquifers and aging oil reservoirs is a valid alter... more Storage of carbon dioxide (CO2) in deep saline aquifers and aging oil reservoirs is a valid alternative approach for reducing the amount of greenhouse gases in the atmosphere. This procedure can be modeled by the combined use of multi-phase fluid flow and wave propagation. The flow simulator is used to model the CO2 injection, and seismic monitoring is applied to determine the spatiotemporal distribution of CO2 after several years of injection. The simultaneous flow of brine and CO2 is modeled with the Black-Oil formulation for two-phase flow in porous media, while wave propagation is formulated using an isotropic viscoelastic model. The CO2 saturation and pressure data computed with the flow simulator is used in a petrophysical model to determine the complex bulk and shear moduli of the formation. Wave propagation is performed using a finite element domain decomposition procedure. The simulation is used to model CO2 injection and flow and compute time-lapse seismograms corresponding to the Utsira aquifer at Sleipner field with the objective of identifying the spatio-temporal distribution of CO2 after injection.

Numerical Simulation in Applied Geophysics, 2016

Fast compressional or shear waves travelling through a fluid-saturated porous material (a Biot me... more Fast compressional or shear waves travelling through a fluid-saturated porous material (a Biot medium) containing heterogeneities on the order of centimeters (mesoscopic scale) suffer attenuation and dispersion observed in seismic data. The mesoscopic loss effect occurs because different regions of the medium may undergo different strains and fluid pressures. This in turn induces fluid flow and Biot slow waves causing energy losses and velocity dispersion. Numerical modeling of wave propagation using Biot's equations of motion takes into account this phenomenon but is computationally very expensive. In the context of Numerical Rock Physics, this chapter presents compressibility and shear time-harmonic experiments to determine an equivalent viscoelastic medium having in the average the same attenuation and velocity dispersion than the original highly heterogeneous Biot medium. Each experiment is associated with a boundary-value problem that is solved using the finite element method.