An epidemic disease caused by a new coronavirus has spread in Northern Italy with strong contagion rate. We implement an SEIR model to compute the infected population and number of casualties this epidemic. The example may ideally regard situation Italian Region Lombardy, where started on February 24, but no means attempts perform rigorous case study view lack suitable data uncertainty different parameters, namely, variation degree home isolation social distancing as function time, initial...

Abstract Heterogeneity of rock's fabric can induce heterogeneous distribution immiscible fluids in natural reservoirs, since the lithological variations (mainly permeability) may affect fluid migration geological time scales, resulting patchy saturation fluids. Therefore, and inhomogeneities both wave propagation. To model effects (attenuation velocity dispersion), we introduce a double double‐porosity model, where pores saturated with two different overlap having dissimilar...

[1] We derive the equations of motion a double-porosity medium based on Biot's theory poroelasticity and generalization Rayleigh's fluid collapse to porous case. Spherical inclusions are imbedded in an unbounded host having different porosity, permeability, compressibility. Wave propagation induces local flow between because their dissimilar compressibilities. Following approach, Lagrange's obtained basis strain kinetic energies. In particular, energy dissipation function associated with...

Polarity reversals in PS and SP images of elastic reverse time migration will cause destructive interference the final stacked results, which may lead to an erroneous interpretation. We derive a polarity reversal correction based on analysis distribution images. The key aspect for is S-wave component. methods can be performed according actual patterns gathers. For 2D isotropic case, sign factor introduced represent component; this computed using energy flux density vector. present procedure...

Abstract The standard Biot‐Gassmann theory of poroelasticity fails to explain strong compressional wave velocity dispersion experimentally observed in 12 tight siltstone with clay‐filled pores. In order analyze and understand the results, we developed a new double‐porosity model clay squirt flow where wave‐induced local fluid occurs between micropores aggregates intergranular macropores. is validated based on combined study ultrasonic experiments specimens at different saturation conditions...

Abstract The fractal texture (or fabric) of porous media, which supports fluid flow at different scales, is the main cause wave anelasticity (dispersion and attenuation) on a wide range frequencies. To model this phenomenon, we develop theory propagation in saturated infinituple‐porosity media containing inclusions multiple based differential effective medium (DEM) solid composites Biot‐Rayleigh for double‐porosity media. dynamical equations are derived from first principles, that is, strain...

Abstract Laboratory experiments on partially saturated rocks show that seismic attenuation can be significant. The main mechanism, wave‐induced local fluid flow (WILFF), is affected by the spatial distribution, especially in conditions of patchy saturation at different scales. We propose a theory to obtain properties based fractal (self‐similar) patches, leading an effective frequency‐dependent modulus. model combines differential medium and Biot‐Rayleigh theories, where patches are...

Abstract We develop a numerical algorithm for simulation of wave propagation in linear nonisothermal poroelastic media, based on Biot theory and generalized Fourier law heat transport analogy with Maxwell model viscoelasticity. A plane analysis indicates the presence classical P S waves two slow waves, namely, thermal modes propagation, which present diffusive behavior under certain conditions, depending viscosity, frequency, thermoelastic constants. The wavefield is computed direct meshing...

Rock-physics templates establish a link between seismic properties (e.g., velocity, density, impedance, and attenuation) reservoir such as porosity, fluid saturation, permeability, clay content. We focus on based attenuation (seismic [Formula: see text] or quality factor), which are highly affected by those properties, we consider carbonate reservoirs that constitute 60% of the world oil reserves potential for additional gas reserves. The described with mesoscopic-loss models, White model...

Seismic wave attenuation has been proved to be an indicator of stress changes in rocks. coda, as a superposition incoherent scattered waves, is known reflect small-scale random heterogeneities the Earth medium. It contains information on Earth's interior, result physical state materials. In this paper, we measure ultrasonic properties rocks under different effective stresses study effect pore-pressure induced coda combination intrinsic and scattering attenuation. We investigate...

We have developed a numerical algorithm for simulation of wave propagation in linear thermoelastic media, based on generalized Fourier law heat transport analogy with Maxwell model viscoelasticity. The wavefield is computed by using grid method the differential operator and two time-integration algorithms to cross-check solutions. Because presence slow quasistatic mode (the thermal mode) makes equations stiff unstable explicit time-stepping methods, first, second-order time-splitting solves...

Petrophysical inversion quantitatively extracts reservoir properties from seismic data/attributes, which has gained increasing attention in assisting hydrocarbon exploration and evaluation. However, given complex reservoirs, its application is limited either due to the adopted rock-physics model or computational demand. We have developed a semianalytic petrophysical method intended for reservoirs. The incorporates double-porosity Biot-Rayleigh (BR) into forward operator, take account...

Wave velocity dispersion and attenuation due to wave-induced fluid flow are important properties for seismic exploration studies of fracture characterization hydrocarbon identification. Existing inversions based primarily on an isotropic theory. However, both anisotropy should also be considered together. Based a model describing attenuation, we introduce frequency-dependent stiffness matrix azimuthal analysis, where the gradient weakness is novel indicator. Then, method inverting amplitude...

The anelastic properties of seismic waves (attenuation and velocity dispersion) in partially saturated rocks depend on the spatial distribution pore fluids. We map fluid distributions three sections a limestone core sample with X-ray computed tomography (CT scans) obtain radii volume fractions gas patches. These statistical data are input into an infinituple-porosity model partial saturation, results which compared forced oscillation (from 0.004 to 100 Hz) ultrasonic (1 MHz) measurements, by...

Abstract Carbonates are characterized by a complex system of pores, caves, vugs and fractures that significantly influence fluid flow the physical behaviors rocks. Six rock samples taken from carbonate reservoir in China's Sichuan Basin to perform computed tomography (CT), X‐ray diffraction thin section analyses. The classified into fractured, fractured‐vuggy pore‐cavity types based on their microstructural properties. Ultrasonic low frequency tests performed with different pressures fluids...

CO2 injection is currently being carried out to improve hydrocarbon recovery and reduce carbon emissions. In this study, we measure the ultrasonic velocity attenuation during supercritical into three oil-saturated tight rock samples (one sandstone two carbonates). The experiments show that P-wave very sensitive pore-fluid substitutions, while shear modulus are independent of it. Using classical Gassmann model, bulk moduli at different saturations obtained from data exceed Gassmann-Voigt...