Stress Relaxing Simulation on Digital Rock: Characterize Attenuation Due To Wave‐Induced Fluid Flow and Scattering

Zhu, Wei Shen; Han, De‐hua; Yang, Zhigang; Cao, Huaigu; Wang, Yirong; Chen, Wei; Shan, Rui

doi:10.1029/2022jb024850

Cited by 7 publications

(1 citation statement)

References 82 publications

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“…However, there is no assumption regarding the fluid distribution, making it more widely applicable. Fluid distribution can be obtained, for instance, from CT scan techniques (e.g., Cadoret et al, 1995;Toms-Stewart et al, 2009;Zhu et al, 2017;2023;Lin et al, 2021;Wang S. et al, 2022a). In a recent study, Chapman et al (2021) measured the velocity dispersion and attenuation in a biphasic saturated sandstone (water and CO2 gas) and obtained the 3D fluid distribution using CT images.…”

Section: Introductionmentioning

confidence: 99%

Prediction of dispersion and attenuation on elastic wave velocities in partially saturated rock based on the fluid distribution obtained from three-dimensional (3D) micro-CT images

Sun,

Fortin,

Tang

et al. 2023

Front. Earth Sci.

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Elastic wave attenuation in partially saturated porous rock is primarily due to wave-induced fluid flow, which arises from the contrast in compressibility between air and water and is influenced by the water distribution within the rock. We propose a method for constructing a numerical model that predicts mesoscopic dispersion and attenuation. Initially, we use fluid distribution data sourced from 3D X-ray Computed Tomography images to construct the numerical model, utilizing Biot’s poroelastic equations as the governing equations. Subsequently, we implement the finite element method to derive solutions for the numerical model. Our focus is centered on two key challenges: 1) reducing memory cost, and 2) efficiently handling element intersection during the meshing process. The solutions illustrate the evolution of fluid pressure distribution and the frequency-dependent advancement of the elastic moduli, coupled with their corresponding attenuation. Ultimately, we compare these numerical predictions with previously published experimental data from a study on partially saturated Indiana limestone. The considerable agreement between our numerical results and the experimental data confirms the validity of our method, which crucially incorporates the actual fluid distribution (captured from 3D CT images) as a vital input.

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Section: Introductionmentioning

confidence: 99%

Prediction of dispersion and attenuation on elastic wave velocities in partially saturated rock based on the fluid distribution obtained from three-dimensional (3D) micro-CT images

Sun,

Fortin,

Tang

et al. 2023

Front. Earth Sci.

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Simulating squirt flow in realistic rock models using graphical processing units (GPUs)

Alkhimenkov

2024

Geophysical Journal International

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Summary Understanding the underlying mechanisms of seismic attenuation and moduli dispersion in fluid-saturated cracked porous rocks is of great importance for the development of non-invasive methods to characterize the subsurface. Wave-induced fluid flow at the pore scale, so-called squirt flow, is responsible for seismic attenuation and moduli dispersion at sonic and ultra-sonic frequencies and may be relevant at seismic frequencies. The squirt flow associated attenuation is usually quantified using analytical models. However, numerical experiments suggest that the squirt flow related dissipation is sensitive to fine details of the pore geometry, which can only be modeled numerically. Most of the existing numerical studies explore this phenomenon using simplified models, and there is a lack of numerical studies that model the physics in realistic pore geometries with sufficient numerical resolution. As a result, the impact of wave-induced fluid flow on the effective static and time-dependent mechanical characteristics in realistic settings is still poorly understood. I address these issues by developing a numerical method to model the effective mechanical properties of a hydro-mechanically coupled system at the pore scale suitable for graphical processing units (GPUs). A numerical evaluation of attenuation and modulus dispersion due to squirt flow in models based on 3D micro-tomography images of cracked Carrara marble is presented. It is shown that the local hydraulic conductivity can be quantitatively estimated from the numerically evaluated effective properties. The accuracy of the numerical results is carefully analyzed. This study improves the understanding of the underlying mechanisms of attenuation and moduli dispersion in fluid-saturated cracked rocks. The new method can be applied to model squirt flow for entire laboratory samples in the centimeter scale which was not possible a decade ago.

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Multiscale pore network modeling and flow property analysis for tight sandstone: a case study

Wu,

Wang,

Xiao

et al. 2023

Journal of Geophysics and Engineering

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Digital rock characterization enables high-fidelity quantification of core samples, facilitating computational studies of physical properties at the microscopic scale. Multiscale tomographic imaging resolves microstructural features from sub-nanometer to millimeter dimensions. However, single-resolution volumes preclude capturing cross-scale morphological attributes due to the inverse relationship between the field of view and resolution. Constructing multiscale, multiresolution, multiphase digital rock model is therefore imperative for reconciling this paradox. We performed multiscale scanning imaging on tight sandstone samples. Based on pore network model integration algorithms, we constructed dual-scale pore network model (PNM) and fracture-pore hybrid network model to analyze their flow characteristics. Results showed that the absolute permeability of the dual-scale PNM exhibited a distinct linear increase with the number of extra cross-scale throats and throat factor, but the rate of increase became smaller when the throat factor exceeded 0.6. For dual-scale pore network with cross-scale throat and throat factor of 1 and 0.7, the predicted porosity matched experimental results well. For the fracture-pore hybrid network model, the relationship between absolute permeability and cross-scale throat properties is similar to the dual-scale PNM. When fluid flow was parallel to the fracture orientation, permeability increased markedly with fracture aperture as a power law function. However, the dip angle did not induce obvious permeability variation trends across different flow directions.

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Stress Relaxing Simulation on Digital Rock: Characterize Attenuation Due To Wave‐Induced Fluid Flow and Scattering

Cited by 7 publications

References 82 publications

Prediction of dispersion and attenuation on elastic wave velocities in partially saturated rock based on the fluid distribution obtained from three-dimensional (3D) micro-CT images

Prediction of dispersion and attenuation on elastic wave velocities in partially saturated rock based on the fluid distribution obtained from three-dimensional (3D) micro-CT images

Simulating squirt flow in realistic rock models using graphical processing units (GPUs)

Multiscale pore network modeling and flow property analysis for tight sandstone: a case study

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