Seismic Spectral Monitoring of CO2 in a Geological Reservoir

Peak frequency is a spectral seismic attribute widely used for reservoir thickness estimation and hydrocarbon detection. In this work we apply this attribute in the context of the geological storage of carbon dioxide (CO2) and analyze its reliability as a thickness estimator for the gas accumulation. To model the vertical distribution of CO2, we solve the Buckley-Leverett equation with discontinuous flux function. A matrix reflectivity algorithm then computes, in the frequency domain, the seismic reflectivity. We find that the peak frequency variability due to CO2 saturation does not alter significantly its correlation with the accumulation thickness. We then extend the applicability of the spectral attribute by examining its time-lapse response to the evolution of the injected CO2 volume within a reservoir. We find that a description of the CO2-brine contact as well as the evaluation of the reservoir’s caprock sealing capacity can be obtained from this implementation. Peak-frequency time-lapse signatures when the CO2 forms an up-going front, evolves into a growing accumulation and leaks into the caprock are identified.Fil: Gómez, Julián Luis. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ravazzoli, Claudia Leonor. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Seismic reflectivity of a carbon dioxide flux

 In the context of the geological storage of carbon dioxide (CO2), thecharacterization of the injected CO2 in a reservoir is of primeimportance for volume capacity evaluation and long-term siteperformance. In this article, we aim to characterize a CO2 accumulationin a deep layered aquifer by means of its seismic reflectivity. Formodeling the vertical distribution of CO2 saturation in the reservoir,we solve the Buckley-Leverett equation with discontinuous flux function,which describes two-phase flow in porous stratified media. To solve thisequation numerically we employ a finite-difference relaxation scheme.The scheme entails an upwinding reconstruction for the spatialderivatives and an implicit-explicit Runge-Kutta scheme for timeintegrations. Once the vertical distribution of CO2 is obtained, we usea matrix propagator algorithm to compute in the frequency domain, thegeneralized reflectivity of the reservoir due to the injected gas. Thebehavior of this reflectivity controls the amplitude of seismic wavereflections and strongly conditions the detectability of the CO2 volumein the space-time domain. The numerical approach used in this article iseasy to implement and allows to quantify the reflectivity of the carbondioxide distribution in a practical way. We show that the frequencybehavior of the reservoir reflectivity may help to interpret thevertical accumulation of CO2, which can be useful as a basis fortime-lapse geophysical monitoring.Fil: Gómez, Julián Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; ArgentinaFil: Ravazzoli, Claudia Leonor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; Argentin

Seismic reflectivity of a carbon dioxide flux

In the context of the geological storage of carbon dioxide (CO2), thecharacterization of the injected CO2 in a reservoir is of primeimportance for volume capacity evaluation and long-term siteperformance. In this article, we aim to characterize a CO2 accumulationin a deep layered aquifer by means of its seismic reflectivity. Formodeling the vertical distribution of CO2 saturation in the reservoir,we solve the Buckley-Leverett equation with discontinuous flux function,which describes two-phase flow in porous stratified media. To solve thisequation numerically we employ a finite-difference relaxation scheme.The scheme entails an upwinding reconstruction for the spatialderivatives and an implicit-explicit Runge-Kutta scheme for timeintegrations. Once the vertical distribution of CO2 is obtained, we usea matrix propagator algorithm to compute in the frequency domain, thegeneralized reflectivity of the reservoir due to the injected gas. Thebehavior of this reflectivity controls the amplitude of seismic wavereflections and strongly conditions the detectability of the CO2 volumein the space-time domain. The numerical approach used in this article iseasy to implement and allows to quantify the reflectivity of the carbondioxide distribution in a practical way. We show that the frequencybehavior of the reservoir reflectivity may help to interpret thevertical accumulation of CO2, which can be useful as a basis fortime-lapse geophysical monitoring.Facultad de Ciencias Astronómicas y Geofísica

Seismic spectral monitoring of CO2 in a geological reservoir

Peak frequency is a spectral seismic attribute widely used for reservoir thickness estimation and hydrocarbon detection. In this work we apply this attribute in the context of the geological storage of carbon dioxide (CO2) and analyze its reliability as a thickness estimator for the gas accumulation. To model the vertical distribution of CO2, we solve the Buckley-Leverett equation with discontinuous flux function. A matrix reflectivity algorithm then computes, in the frequency domain, the seismic reflectivity. We find that the peak frequency variability due to CO2 saturation does not alter significantly its correlation with the accumulation thickness. We then extend the applicability of the spectral attribute by examining its time-lapse response to the evolution of the injected CO2 volume within a reservoir. We find that a description of the CO2-brine contact as well as the evaluation of the reservoir’s caprock sealing capacity can be obtained from this implementation. Peak-frequency time-lapse signatures when the CO2 forms an up-going front, evolves into a growing accumulation and leaks into the caprock are identified.Facultad de Ciencias Astronómicas y Geofísica

Reflection characteristics of linear carbon dioxide transition layers

Seismic monitoring of underground CO2 accumulations is a subject of growing interest in applied geophysics. Due to their large impedance contrasts, attention is focused on accumulations of high CO2 saturation in most cases. However, low-saturation zones with dispersed carbon dioxide, or saturation transition layers, may have an important role inthe propagation of waves within the reservoir, giving rise to amplitude and phase changes of the seismic signals. With this motivation, we studied the reflectivity response of a simple reservoir model with a given CO2 saturation-depth profile, on a theoretical basis. We investigated the influence of the overall saturation, vertical extent, and spatial fluiddistribution of a carbon dioxide transition zone in the reflectivity of a reservoir. The parametric analysis entails the computation of the generalized P-wave reflection coefficient and its variations with ray angle (AVA) and frequency (AVF). The combined analysis of AVA and AVF can help to characterize and monitor CO2 transition layers within geological storage sites.Fil: Gómez, Julián Luis. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Ravazzoli, Claudia Leonor. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Geofísica Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

On the static and dynamic behavior of fluid saturated composite porous solids: A homogenization approach

The macroscopic description of the dynamical behavior of a porous solid composed of two nonwelded solid phases saturated by a single-phase fluid is derived using two-space homogenization techniques for periodic structures. The pore size is assumed to be small compared to the macroscopic scale under consideration. At the microscopic scale the two solids are described by the linear elastic equations, and the fluid by the linearized Navier-Stokes equations, with appropriate boundary conditions at the solid-solid and solid-fluid interfaces. The nonwelded interface between the two solid phases is represented by displacement and/or velocity discontinuities proportional to the stresses across the interface, while the stresses are assumed to be continuous. After performing the homogenization procedure, constitutive relations, Darcy's and Biot's type dynamic equations for the saturated composite porous material are obtained.Facultad de Ciencias Astronómicas y Geofísica

Identification of velocity variations in a seismic cube using neural networks

This research allow to infer that from seismic section and well data it is possible to determine velocity anomalies variations in layers with thicknesses below to the seismic resolution using neuronal networks.Applications in Artificial Intelligence - Learning and Neural NetsRed de Universidades con Carreras en Informática (RedUNCI

Análisis petro-elástico de velocidades P y S en muestras de la formación Vaca Muerta

La formación Vaca Muerta es una de las principales rocas madre en la cuenca Neuquina, la que durante los últimos años ha cobrado gran notoriedad y relevancia como reservorio para la producción de hidrocarburos no convencionales. La misma está constituida por sedimentitas marinas tipo shales, denominadas margas bituminosas, debido a su alto contenido de materia orgánica. Con el fin de lograr una completa caracterización de estos reservorios, la empresa YPF realizó a partir de 2010 estudios petrofísicos, mineralógicos, geoquímicos, geomecánicos y ultrasónicos sobre un conjunto de muestras de tal formación, extraídas a partir de testigos de pozos. Asimismo, efectuaron análisis PVT para la tipificación de los fluidos del reservorio a la temperatura y presión in situ. La integración de tal conjunto de datos para la calibración de modelos de física de rocas apropiados para estos ambientes constituye la principal motivación de este trabajo. Esta temática ha despertado el interés de numerosos autores quienes han propuesto diversos modelos físicos y workflows para respresentar el comportamiento elástico de estos medios, los que por lo general exhiben anisotropía transversal. Los diferentes modelos tienen el fin de relacionar los parámetros de interés en estos ambientes con las magnitudes observables, tales como velocidades sísmicas, densidad, impedancias elásticas y reflectividades. En el presente trabajo se testean diferentes teorías de medios elásticos y poroelásticos efectivos, integrando la información disponible a los modelos. Considerando la hipótesis de isotropía como primer aproximación, el objetivo consistirá en comparar el grado de ajuste de las velocidades medidas en laboratorio sobre un conjunto de muestras seleccionadas (correspondientes a un mismo pozo), para los diferentes modelos. Como resultado de este análisis se espera correlacionar los errores resultantes de las distintas aproximaciones con la fracción orgánica y de arcillas de las distintas muestras. Asimismo, se analizará la factibilidad de establecer un valor de porosidad crítica razonable para el intervalo en estudio.Eje: Geofísica Aplicada y Ambiental.Facultad de Ciencias Astronómicas y Geofísica

A Numerical Model for the Study of the Load Effect of the Water in the Area of the River Plate

We present a simplified geophysical model to evaluate the deformation field of the local lithosphere during a marked swell of the River Plate. The influence of this phenomenon on the displacement field is analyzed. The differential equations of elastic equilibrium were solved by means of a three dimensional finite element method with appropiate boundary conditions. The results obtained indicate that very high precision measurements would be neccesary to quantify these effects. This, in turn, would allow us to improve the estimation of the elastic parameters of the area.Facultad de Ciencias Astronómicas y Geofísica

On the static and dynamic behavior of fluid saturated composite porous solids: A homogenization approach

The macroscopic description of the dynamical behavior of a porous solid composed of two nonwelded solid phases saturated by a single-phase fluid is derived using two-space homogenization techniques for periodic structures. The pore size is assumed to be small compared to the macroscopic scale under consideration. At the microscopic scale the two solids are described by the linear elastic equations, and the fluid by the linearized Navier-Stokes equations, with appropriate boundary conditions at the solid-solid and solid-fluid interfaces. The nonwelded interface between the two solid phases is represented by displacement and/or velocity discontinuities proportional to the stresses across the interface, while the stresses are assumed to be continuous. After performing the homogenization procedure, constitutive relations, Darcy's and Biot's type dynamic equations for the saturated composite porous material are obtained.Facultad de Ciencias Astronómicas y Geofísica