المؤلفون: Li, Yang, Brossier, Romain, Métivier, Ludovic

المساهمون: Laboratoire d'automatique et de génie des procédés (LAGEP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Supérieure de Chimie Physique Électronique de Lyon (CPE)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement IRD : UR219-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Equations aux Dérivées Partielles (EDP ), Laboratoire Jean Kuntzmann (LJK ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )

المصدر: SEG Technical Program Expanded Abstracts 2019 ; SEG 2019 annual meeting ; https://hal.science/hal-02325586Test ; SEG 2019 annual meeting, Sep 2019, San Antonio, United States. pp.3770-3774, ⟨10.1190/segam2019-3215003.1⟩

مصطلحات موضوعية: frequency-domain, 3D, elastic, modeling, wave propagation, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation

جغرافية الموضوع: San Antonio, United States

الوقت: San Antonio, United States

الوصف: International audience ; A feasibility study on 3D frequency-domain anisotropic elastic wave modeling is conducted. The spectral element method is applied to discretize the 3D frequency-domain anisotropic elastic wave equation and the linear system is solved by parallel direct solvers, MUMPS andWSMP. A hybrid implementation of MPI and OpenMP for MUMPS is shown to be more efficient in flops and memory cost during the factorization. The influence of complex topography on MUMPS performance is negligible. With available resources, the largest scale modeling, 30 wavelengths in each dimension, is achieved. Using the block lowrank feature ofMUMPSleads to computational gains compared with the full-rank version. Limitation of MUMPS scalability for large number of MPI processes prompts us to investigate the performance of an alternative linear solver,WSMP. Preliminary comparison on small scale modelings shows a better scalability of WSMP while being more computational demanding.

العلاقة: hal-02325586; https://hal.science/hal-02325586Test; https://hal.science/hal-02325586/documentTest; https://hal.science/hal-02325586/file/2019_SEG_Li_FDSEM_submitted.pdfTest

الإتاحة: https://doi.org/10.1190/segam2019-3215003.1Test
https://hal.science/hal-02325586Test
https://hal.science/hal-02325586/documentTest
https://hal.science/hal-02325586/file/2019_SEG_Li_FDSEM_submitted.pdfTest

المؤلفون: Mohammad Sarmadivaleh, Tobias M. Müller, Rupeng Ma, Jimmy X. Li, Reza Rezaee, Mahyar Madadi

المصدر: GEOPHYSICS. 87:MR177-MR187

مصطلحات موضوعية: Physics::Fluid Dynamics, Condensed Matter::Soft Condensed Matter, Materials science, Geophysics, Wave propagation, Geochemistry and Petrology, Attenuation, Wetting, Composite material, Porous medium, Characterization (materials science)

الوصف: Understanding seismic wave propagation in granular porous media is important for subsurface characterization. The presence of fluids, their distribution, and the prevailing wettability condition result in additional complexities. Although it is known that wave propagation in dry granular porous media is dominated by the presence of force chains, their influence in (partially) saturated granular porous media with different wettability conditions remains largely unexplored. To make progress in this direction, we have designed laboratory experiments by combining core flooding and ultrasonic measurements in glass bead packings that are chemically treated to alternate the wettability. The P- and S-wave velocity-saturation relation and attenuation-saturation relation are retrieved from the waveforms for water- and gas-wetting samples. The results demonstrate that there is a transition from an attenuating but stable P-wave pulse at low and moderate saturation to a set of incoherently scattered waves at high saturation. The incoherent scattering in the gas-wetting case is negligibly small, whereas it is more pronounced in the water-wetting case. We interpret these observations in terms of the wettability-dependent ability for water to penetrate into grain contacts. In the water-wetting case, liquid bridges are thought to locally reinforce the force chains and to increase their characteristic length scale. This leads to an increase in P-wave velocity and promotes incoherent scattering because the ratio of dominant wavelength to characteristic length scale decreases. In the gas-wetting case, however, the presence of gas prevents the water from direct contact with the glass beads and therefore stops the formation and growth of the liquid bridges within the force-chain network.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::d2457dae1d03efde763444da1bd05685Test
https://doi.org/10.1190/geo2021-0279.1Test

المؤلفون: Wei Zhang, Xiaofei Chen, Nan Zang

المصدر: GEOPHYSICS. 86:T277-T292

مصطلحات موضوعية: Physics, Curvilinear coordinates, Wave propagation, Mathematical analysis, Finite difference, Finite difference algorithm, 010502 geochemistry & geophysics, Grid, 01 natural sciences, Physics::Geophysics, 010101 applied mathematics, Geophysics, Geochemistry and Petrology, Free surface, 0101 mathematics, Overset grid, Elastic wave propagation, 0105 earth and related environmental sciences

الوصف: We have developed an overset-grid algorithm to simplify the difficulty of curvilinear grid (CG) generation and increase the computational efficiency for seismic wavefield modeling by using the finite-difference method in areas with complex surface topography. The overset grid comprises a Cartesian grid block and an approximately orthogonal CG block. The Cartesian grid covers most of the simulation domain, whereas the CG discretizes the near-surface topography. The Cartesian grid and the CG overlap each other arbitrarily. We use sixth-order explicit Lagrangian interpolation to exchange data between the Cartesian grid and the CG, which is shown to be sufficiently accurate. We also find that spatially smoothing the source term is important for reducing strong artificial reflections when the source is near the overlapping zone. Finally, numerical tests are performed to verify that the proposed overset grid is well suited for effective numerical simulation of seismic wave propagation.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::45bc5851f99f91ea01d1a6b70fa5e3acTest
https://doi.org/10.1190/geo2020-0915.1Test

المؤلفون: Wei Zhang, Chunli Zhang

المصدر: GEOPHYSICS. 87:T29-T42

مصطلحات موضوعية: Geophysics, Computer simulation, Geochemistry and Petrology, Adaptive mesh refinement, Acoustics, Numerical analysis, Seismic wave propagation, Finite difference, Acoustic wave, Grid, Geology

الوصف: The finite-difference method (FDM) is one of the most popular numerical methods to simulate seismic wave propagation in complex velocity models. If a uniform grid is applied in FDM for heterogeneous models, the grid spacing is determined by the global minimum velocity to suppress dispersion and dissipation errors in the numerical scheme, resulting in spatial oversampling in higher velocity zones. Then, the small grid spacing dictates a small time step due to the stability condition of explicit numerical schemes. The spatial oversampling and reduced time step will cause unnecessarily inefficient use of memory and computational resources in simulations for strongly heterogeneous media. To overcome this problem, we have used the adaptive mesh refinement (AMR) technique in the FDM to flexibly adjust the grid spacing following velocity variations. AMR is rarely used in acoustic wave simulations with the FDM due to the increased complexity of implementation, including its data management, grid generation, and computational load balancing on high-performance computing platforms. We implement AMR for 2D acoustic wave simulation in strongly heterogeneous media based on the patch approach with FDM. The AMR grid can be automatically generated for given velocity models. To simplify the implementation, we use a well-developed AMR framework, AMReX, to carry out the complex grid management. Numerical tests determine the stability, accuracy level, and efficiency of the AMR scheme. The computation time is approximately proportional to the number of grid points, and the overhead due to the wavefield exchange and data structure is small.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::0acaa1e0e855ef23d8451e43a7b02725Test
https://doi.org/10.1190/geo2020-0801.1Test

المؤلفون: Yanqi Wu, Jianwei Ma

المصدر: GEOPHYSICS. 87:T1-T13

مصطلحات موضوعية: Physics, Couple stress, Wave propagation, Linear elasticity, Mechanics, Wave equation, symbols.namesake, Geophysics, Geochemistry and Petrology, Surface wave, Dispersion (optics), symbols, Rayleigh wave, Scale effect

الوصف: In elastostatics, the scale effect is a phenomenon in which the elastic parameters of a medium vary with the specimen size when the specimen is sufficiently small. Linear elasticity cannot explain the scale effect because it assumes that the medium is a continuum and does not consider microscopic rotational interactions within the medium. In elastodynamics, wave-propagation equations are usually based on linear elasticity. Thus, nonlinear elasticity must be introduced to study the scale effect on wave propagation. We have developed one of the generalized continuum theories, a so-called couple-stress theory, into solid earth geophysics to build a more practical model of the underground medium. The first-order velocity-stress wave equation is derived to simulate the propagation of Rayleigh waves. Body and Rayleigh waves are compared using elastic theory and couple-stress theory in a homogeneous half-space and a layered space. The results indicate that couple stress causes the dispersion of surface waves and S-waves even in a homogeneous half-space. The effect is enhanced by increasing the source frequency and characteristic length, despite its insufficiently clear physical meaning. Rayleigh waves are more sensitive to the couple-stress effect than are body waves. Based on the phase-shifting method, it is determined that Rayleigh waves exhibit different dispersion characteristics in the couple-stress theory than in the conventional elastic theory. For the fundamental mode, dispersion curves tend to move to a lower frequency with an increase in characteristic length [Formula: see text]. For the higher modes, the dispersion curve energy is stronger with a greater characteristic length [Formula: see text].

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::fe64b4060b99d9b0f31fad6a6f5d152bTest
https://doi.org/10.1190/geo2020-0890.1Test

المؤلفون: Alexey Stovas, Shibo Xu

المصدر: GEOPHYSICS. 87:C31-C38

مصطلحات موضوعية: Physics, Geophysics, Geochemistry and Petrology, Wave propagation, Explicit model, Mathematical analysis, Orthorhombic crystal system, Extension (predicate logic), Kinematics, Characterization (mathematics), Anisotropy, Physics::Geophysics, Characterization (materials science)

الوصف: Understanding the kinematics of horizontally layered reservoir rocks is important to their proper characterization; to accomplish this, it is necessary to specify the explicit model for these kinematic properties. Accurate approximations for traveltime and relative geometric spreading in an elastic homogeneous orthorhombic (ORT) model have been investigated with different forms: shifted hyperbola form (SHF), Taylor series, and the rational form. We have extended these approximations to the multilayered ORT model by adopting composite coefficients and effective model parameters. The multilayered model is characterized without and with the azimuthal variation among layers. There is an overdetermined problem when the azimuthal variation exists; to address that case, the least-squares method is adopted. To check the feasibility of the expansion, we select the SHF approximation specified in the homogeneous elastic ORT model for the calculation in the numerical example. Four groups of examples are analyzed to investigate the influence on the accuracy of the approximation with the change in rotation angle, degree of anisotropy, and the direction of the orientation. The results indicate that, for the multilayer, the accuracy of the approximation is proportional to the degree of anisotropy and the value of the angle of rotation. The relative errors in traveltime and relative geometric spreading in this multilayered extension are very small and can be implemented in practical applications.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::7b503d878fe62d5def85c06d88164f2eTest
https://doi.org/10.1190/geo2021-0023.1Test

المؤلفون: Tobias M. Müller, Josue G. González, Pratap N. Sahay

المصدر: GEOPHYSICS. 86:MR315-MR324

مصطلحات موضوعية: Physics, Diffusion equation, Wave propagation, Poromechanics, Mechanics, Classification of discontinuities, Vorticity, Physics::Geophysics, Physics::Fluid Dynamics, Shear (sheet metal), Geophysics, Geochemistry and Petrology, S-wave, Newtonian fluid

الوصف: The shear motion in Newtonian fluids, that is, the fluid vorticity, represents an intrinsic loss mechanism governed by a diffusion equation. Its description involves the trace-free part of the fluid viscous stress tensor. This part is missing in the Biot theory of poroelasticity. As a result, the fluid vorticity is not captured and only one shear wave (S-wave) is predicted. The missing fluid vorticity has implications for the propagation of S-waves across discontinuities. This becomes most apparent in the problem of S-wave propagation across the welded contact of an elastic solid with a porous medium. At such a contact, the no-slip condition between the elastic solid and the constituent parts of the porous medium, the solid frame and the pore fluid, must hold. This requirement translates into a vanishing relative motion of the fluid with respect to the solid frame, that is, the filtration field, at the contact. Nevertheless, our analysis indicates that for the Biot theory, in the low-frequency regime, a nonzero, although insignificantly small, filtration field exists at the contact. However, more importantly, the filtration field is noticeable when the transition to the high-frequency regime occurs. This constitutes a disagreement with the requirement of a no-slip boundary condition and renders the prediction unphysical. This shortcoming is circumvented by including the fluid viscous stress tensor into the poroelastic constitutive relations, as stipulated by the de la Cruz-Spanos poroelasticity theory. Then, a second S-wave is predicted that manifests as the fluid vorticity at the macroscale. This process is distinct from the fast S-wave, the other predicted S-wave akin to the Biot S-wave. We find that the generation of this process at the contact induces a filtration field equal and opposite to that associated with the fast S-wave. Therefore, the no-slip condition is satisfied and the S-wave reflection/transmission across a discontinuity becomes physically meaningful.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::837d9dc8991e9d7c98af8f6b2aa4c221Test
https://doi.org/10.1190/geo2021-0284.1Test

المؤلفون: Dawei Liu, Wenchao Chen, Xiaokai Wang, Lei Gao

المصدر: GEOPHYSICS. 86:V509-V523

مصطلحات موضوعية: Physics, Footprint (electronics), Geophysics, Geochemistry and Petrology, Attenuation, Seismic attribute, Reservoir modeling, Atom (order theory), Interference (wave propagation), Dictionary learning, Computational physics

الوصف: The acquisition footprint causes serious interference with seismic attribute analysis, which severely hinders accurate reservoir characterization. Therefore, acquisition footprint suppression has become increasingly important in industry and academia. We have assumed that the time slice of 3D poststack migration seismic data mainly comprises two components: useful signals and the acquisition footprint. Useful signals describe the spatial distributions of geologic structures with local piecewise smooth morphological features. However, the acquisition footprint often behaves as periodic artifacts in the time-slice domain. In particular, the local morphological features of the acquisition footprint in marine seismic acquisition appear as stripes. Because useful signals and the acquisition footprint have different morphological features, we can train an adaptive dictionary and divide the atoms of the dictionary into two subdictionaries to reconstruct these two components. We have devised an adaptive dictionary learning method for acquisition footprint suppression in the time slice of 3D poststack migration seismic data. To obtain an adaptive dictionary, we use the K-singular value decomposition algorithm to sparsely represent the patches in the time slice of 3D poststack migration seismic data. Each atom of the trained dictionary represents certain local morphological features of the time slice. According to the difference in the variation level between the horizontal and vertical directions, the atoms of the trained dictionary are divided into two types. One type significantly represents the local morphological features of the acquisition footprint, whereas the other type represents the local morphological features of useful signals. Then, these two components are reconstructed using morphological component analysis based on different types of atoms, respectively. Synthetic and field data examples indicate that our method can effectively suppress the acquisition footprint with fidelity to the original data.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::6d2e3f39a84029ec7d8ce03100e18b3eTest
https://doi.org/10.1190/geo2020-0681.1Test

المؤلفون: Lei Wen, Zhuang Subin, Xinru Mu, Jianping Huang

المصدر: GEOPHYSICS. 86:T487-T507

مصطلحات موضوعية: Spatial variable, Physics, Geophysics, Geochemistry and Petrology, Wave propagation, Attenuation, Mathematical analysis, Phase (waves), Order (group theory), P-wave, Fractional Laplacian, Wave equation

الوصف: We have developed a new time-domain viscoacoustic wave equation for simulating wave propagation in anelastic media. The new wave equation is derived by inserting the complex-valued phase velocity described by the Kjartansson attenuation model into the frequency-wavenumber domain acoustic wave equation. Our wave equation includes one second-order temporal derivative and two spatial variable-order fractional Laplacian operators. The two fractional Laplacian operators describe the phase dispersion and amplitude attenuation effects, respectively. To facilitate the numerical solution for our wave equation, we use the arbitrary-order Taylor series expansion (TSE) to approximate the mixed-domain fractional Laplacians and achieve the decoupling of the wavenumber and the fractional order. Then, our viscoacoustic wave equation can be directly solved using the pseudospectral method. We adopt a hybrid pseudospectral/finite-difference method (HPSFDM) to stably simulate wave propagation in arbitrarily complex media. We validate the high accuracy of our approximate dispersion term and approximate the dissipation term in comparison with the accurate dispersion term and accurate dissipation term. The accuracy of the numerical solutions is evaluated by comparison with the analytical solutions in homogeneous media. Theory analysis and simulation results indicate that our viscoacoustic wave equation has higher precision than the traditional fractional viscoacoustic wave equation in describing constant- Q attenuation. For a model with Q

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::79966d738e917ed49ff67145658b5ec4Test
https://doi.org/10.1190/geo2020-0610.1Test

المؤلفون: Xiao-Ming Tang, He-Ming Wang

المصدر: GEOPHYSICS. 86:A57-A62

مصطلحات موضوعية: Geophysics, Materials science, Geochemistry and Petrology, Wave propagation, S-wave, Inversion (geology), Spectrum (functional analysis), Ultrasonic sensor, Composite material, Dispersion (water waves), Porous medium, Aspect ratio (image), Physics::Geophysics

الوصف: Subsurface rocks contain pores and cracks of various sizes. The cracked porous medium elastic wave theory that describes wave propagation characteristics due to the pore-crack interaction is extended to include cracks of different aspect ratios. The extended theory is applied to model P- and S-wave velocity data of dry and fluid-saturated rock under pressure loading conditions, so as to determine the pore-aspect-ratio spectrum through an inversion procedure. The inversion result is consistent with that from the scanning electron microscope analysis, showing significant improvement versus previous inversion. The inverted pore-aspect-ratio spectrum is input into the wave theory to predict the velocity dispersion of the rock in the full frequency range. The predicted dispersion and its variation trend with pressure agree with the data measured in the (2–200, 106) Hz range at various differential pressures, whereas the modeling using a single-aspect-ratio theory has difficulty matching the data. This research work provides not only a method for analyzing the pore structure characteristics of rocks from the laboratory ultrasonic velocity data, but also a way to predict the seismic wave dispersion from the data.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::e3f896838525cf3970a55c241d60617aTest
https://doi.org/10.1190/geo2021-0071.1Test