Acoustic and mechanical response of reservoir rocks under variable saturation and effective pressure

We investigate the acoustic and mechanical properties of a reservoir sandstone saturated by two immiscible hydrocarbon fluids, under different saturations and pressure conditions. The modeling of static and dynamic deformation processes in porous rocks saturated by immiscible fluids depends on many parameters such as, for instance, porosity, permeability, pore fluid, fluid saturation, fluid pressures, capillary pressure, and effective stress. We use a formulation based on an extension of Biot's theory, which allows us to compute the coefficients of the stress-strain relations and the equations of motion in terms of the properties of the single phases at the in situ conditions. The dry-rock moduli are obtained from laboratory measurements for variable confining pressures. We obtain the bulk compressibilities, the effective pressure, and the ultrasonic phase velocities and quality factors for different saturations and pore-fluid pressures ranging from normal to abnormally high values. The objective is to relate the seismic and ultrasonic velocity and attenuation to the microstructural properties and pressure conditions of the reservoir. The problem has an application in the field of seismic exploration for predicting pore-fluid pressures and saturation regimes

The role of agency in the emergence and development of social innovations in rural areas. Analysis of two cases of social farming in Italy and the Netherlands

Social innovation is considered a relevant concept to tackle societal challenges and needs in rural areas and to promote smart, inclusive and sustainable growth. The characterising sector of rural areas is agriculture; therefore, the focus of this paper is on social innovation in the field of social farming. Among the many factors leading to the emergence and development of social innovation, agency has been considered relevant in the literature on transformability and transformative social innovation as it is the ability to turn contextual difficulties into opportunities for social innovation and for inclusive growth. This paper proposes an evaluation framework to assess the different dimensions of agency by triangulating quantitative with qualitative data and by using indicators. This paper adopts a case study approach, analysing two cases of social farming in Italy and the Netherlands. The results show that the social innovation idea and the resilience of the agency are among the most relevant dimensions for the emergence and development of social innovations. Finally, this paper discusses the three most relevant factors for agency to lead to social innovation: idea and embeddedness of the agency, transformability of the context through agencys resilience, and agency as catalyst for empowerment

Evaluating the Impact of an Integrated Urban Design of Transport Infrastructure and Public Space on Human Behavior and Environmental Quality: A Case Study in Beijing

Urban transport infrastructure can result in the physical, psychological and environmental separation of neighborhoods, public spaces and pedestrian networks, leading to negative impacts on citizens’ daily commutes, social activities and the quality of the ecosystem. An integrated design of transport infrastructure and public space is beneficial for mediating these negative impacts. In this paper, we propose an integrated methodology, which combines urban design, computational scenario evaluation and decision-making processes, based on a conceptual model of human and ecological needs-driven planning. To evaluate the impacts of the road network and public space design on individual outdoor activities, travel behavior and air pollution, an agent-based model is demonstrated. This model is then applied to a case study in Beijing, leading to hourly traffic volume maps and car-related air pollution heat maps of a baseline road network-public space design

Tragitti gaddiani

L'articolo è dedicato a una verifica di temi e strutture della narrativa gaddiana, tra teoria e prassi narratologica, a partire da "Racconto italiano di ignoto del Novecento"

Caracterización gravimétrica de la cuenca del Golfo San Jorge

La Cuenca del Golfo San Jorge se encuentra ubicada en la porción central de la Patagonia, entre los 45° y 47° de latitud Sur y entre los 66° y 71° de longitud Oeste. Es una cuenca elongada en dirección Este - Oeste que abarca las porciones Sur de la provincia de Chubut y Norte de la provincia de Santa Cruz y continúa al Este en la plataforma continental, cubriendo una superficie de aproximadamente 180.000 km2, de los cuales una tercera parte corresponde al sector de costa afuera. La aplicación de distintos métodos geofísicos permite obtener información de la distribución de las propiedades físicas y estructuras internas del área de estudio. Uno de los métodos geofísicos clásicamente utilizados en ambientes de cuenca es el método gravimétrico de exploración, que se basa en la medición de variaciones muy pequeñas del campo gravitatorio terrestre causadas por heterogeneidades laterales de densidad dentro del subsuelo. En este trabajo se describe el procesamiento y la integración de los datos gravimétricos terrestres provistos por la empresa YPF S.A., medidos sobre la Cuenca del Golfo San Jorge, junto con información geológica y de pozos de la zona. Esto permitió la construcción de modelos geofísicos confiables tanto 2D como 3D para las estructuras del subsuelo a largo de toda la cuenca, para lo cual se utilizó también una técnica de inversión estructural tridimensional. Los modelos obtenidos permitieron caracterizar la geometría del basamento a escala regional y la posición y profundidad de los depocentros sedimentarios más importantes de la cuenca, lo que no se había hecho hasta el momento.Facultad de Ciencias Astronómicas y Geofísica

A constitutive equation and generalized Gassmann modulus for multimineral porous media

We derive the time-domain stress-strain relation for a porous medium composed of n - 1 solid frames and a saturating fluid. The relation holds for nonuniform porosity and can be used for numerical simulation of wave propagation. The strain-energy density can be expressed in such a way that the two phases (solid and fluid) can be mathematically equivalent. From this simplified expression of strain energy, we analogize two-, three-, and n-phase porous media and obtain the corresponding coefficients (stiffnesses). Moreover, we obtain an approx imation for the generalized Gassmann modulus. The Gassmann modulus is the bulk modulus of a saturated porous medium whose matrix (frame) is homogeneous. That is, the medium consists of two homogeneous constituents: a mineral composing the frame and a fluid. Gassmann's modulus is obtained at the low-frequency limit of Biot's theory of poroelasticity. Here, we assume that all constituents move in phase, a condition similar to the dynamic compatibility condition used by Biot, by which the P-wave velocity is equal to Gassmann's velocity at all frequencies. Our results are compared with those of the Berryman-Milton (BM) model, which provides an exact generalization of Gassmann's modulus to the three-phase case. The model is then compared to the wet-rock moduli obtained by static finite-element simulations on digitized images of microstructure and is used to fit experimental data for shaly sandstones. Finally, an example of a multimineral rock (n > 3) saturated with different fluids is given.Fil: Carcione, Jose M.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; ItaliaFil: Helle, Hans B.. Norsk Hydro; NoruegaFil: Santos, Juan Enrique. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto del Gas y del Petróleo; 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; Argentin

Numerical simulation of ultrasonic waves in reservoir rocks with patchy saturation and fractal petrophysical properties

We simulate the propagation of ultrasonic waves in heterogeneous poroviscoelastic media saturated by immiscible fluids. Our model takes into account capillary forces and viscous and mass coupling effects between the fluid phases under variable saturation and pore fluid pressure. The numerical problem is solved in the space–frequency domain using a finite element procedure and the time–domain solution is obtained by a numerical Fourier transform. Heterogeneities due to fluid distribution and rock porosity–permeability are modeled as stochastic fractals, whose spectral densities reproduce saturation an petrophysical variations similar to those observed in reservoir rocks. The numerical experiments are performed at a central frequency of 500 kHz, and show clearly the effects of the different heterogeneities on the amplitudes of shear and compressional waves and the importance of wave mode conversions at the different interfaces.Facultad de Ciencias Astronómicas y Geofísica