Article
Engineering, Geological
Min Chen, Shakil Masum, Sivachidambaram Sadasivam, Hywel Thomas
Summary: This study proposes an effective stress model for investigating the anisotropy of coal swelling in fractured porous media. The model considers the change in stress on the solid-fluid interface induced by gas adsorption. Experimental results show that coal swelling is greater in the direction perpendicular to the bedding plane than in the parallel plane. The evolution of anisotropic stress-dependent permeability behavior is described by direction dependent fracture compressibility. The presented model provides a tool for quantifying gas adsorption-induced anisotropic coal swelling and permeability behaviors.
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES
(2022)
Article
Geosciences, Multidisciplinary
Arqam Muqtadir, Saud Al-Dughaimi, Taqi Alzaki, Jack Dvorkin
Summary: This study compares the P-wave and S-wave velocities obtained under different hydrostatic loading conditions using ultrasonic pulse transmission experiments. The results show significant differences in velocities when a smaller hydrostatic stress is added to axial stress, but these differences become smaller as the hydrostatic stress increases. The findings suggest that laboratory hydrostatic experiments can be used for in-situ velocity estimates even under strong in-situ contrasts between the vertical and horizontal stresses.
FRONTIERS IN EARTH SCIENCE
(2022)
Article
Computer Science, Interdisciplinary Applications
Eleni Gerolymatou, Julia Leuthold
Summary: This study investigates the oedometric compaction of materials with collapsible structure from a numerical point of view and finds that the reduction in permeability following the formation of compaction bands can be highly anisotropic. By using the finite element method and implementing a nonlocal formulation, the numerical stability issue caused by the localization of deformation is resolved.
COMPUTERS AND GEOTECHNICS
(2021)
Article
Engineering, Chemical
Yutian Feng, Hongming Tang, Haoxuan Tang, Yijiang Leng, Xuewen Shi, Jia Liu
Summary: This paper investigates the petrophysical characteristics of the Wufeng-Longmaxi shale formation in the Sichuan Basin, focusing on the acoustic wave velocity and elastic anisotropy, and their stress sensitivity mechanisms. The results show that the wave velocity and anisotropy are influenced by the confining pressure, and the stress sensitivity coefficients differ between P-wave and S-wave. The study provides an empirical formula for predicting the anisotropy parameters under different pressures, which is important for the interpretation and prediction of shale gas reservoirs.
Article
Nanoscience & Nanotechnology
B. Ernst, S. Keim, U. Tetzlaff
Summary: The influence of orientation on the indentation modulus, hardness, and creep properties of high purity 6-Sn (wt.%: 99.999) was examined using nanoindentation methods. Crystal orientations close to < 100 >, < 110 >, and < 001 > were identified, and continuous stiffness measurements (CSM) and constant load creep tests were performed. The results indicated an orientation dependence in the indentation modulus, hardness, and creep properties.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2022)
Article
Engineering, Geological
Kang Duan, Xuejian Li, Chung-Yee Kwok, Qiangyong Zhang, Luchao Wang
Summary: A novel physics-based numerical model is proposed to simulate the orientation and effective confining pressure dependent permeability of anisotropic rock. The study reveals that the macro permeability decreases with increasing effective stress, and permeability anisotropy is caused by different apertures and force sensitivity factors assigned to the rock matrix and bedding. The model successfully captures the hydro-mechanical coupled responses of anisotropic rock formation, providing insights into the mechanisms underlying stress-dependent permeability and engineering responses.
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES
(2021)
Article
Geochemistry & Geophysics
Yuhui He, Yan Lu
Summary: Using Pn tomography with coordinate rotation, a new Pn velocity and anisotropy model was obtained for imaging in Alaska and adjacent areas. The study found correlations between observed Pn velocities and local geological structures, as well as low velocities beneath the Aleutian volcanic arc potentially revealing plate dehydration-related partial melting. A slab tear was suggested by the separation of low velocities by a high-velocity anomaly, indicating complex deformation beneath Alaska and adjacent areas.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Geosciences, Multidisciplinary
Quinn C. Wenning, Claudio Madonna, Alba Zappone, Melchior Grab, Antonio P. Rinaldi, Michael Plotze, Christophe Nussbaum, Domenico Giardini, Stefan Wiemer
Summary: This study focuses on the structural and petrophysical characterization of the Opalinus Clay host rock and fault core, with implications for geological carbon sequestration and nuclear waste disposal. The research suggests similarities in matrix permeability and seismic velocity measurements between the host rock and Main Fault.
JOURNAL OF STRUCTURAL GEOLOGY
(2021)
Article
Geochemistry & Geophysics
Alexey Stovas, Yuriy Roganov, Vyacheslav Roganov
Summary: The phase and group velocity surfaces play a crucial role in wave propagation in anisotropic media, especially for shear waves. It is important to identify features in both the phase and group domains to analyze wave propagation in an anisotropic model. The proposed characteristics, such as the energy flux angle and enhancement factor, help characterize singularity points and triplication zones in anisotropic models.
GEOPHYSICAL PROSPECTING
(2021)
Article
Engineering, Chemical
Jiaqi Li, Song Lei, Bixin Deng, Jian Xue, Yanjie Wang, Haihui Wang
Summary: This study prepared a series of dense membranes of K2NiF4-type materials by adjusting grain size, revealing a unique relationship curve between oxygen permeation flux and grain size. It further demonstrated that grain size plays a significant role in influencing the oxygen permeability of membranes.
JOURNAL OF MEMBRANE SCIENCE
(2021)
Article
Energy & Fuels
Mahmoud Khadijeh, Alissar Yehya, Elsa Maalouf
Summary: This study analyzes the efficiency of hydraulic fracturing operations using numerical models and experimental studies. It finds that in vertically transversely isotropic (VTI) formations, the expansion of cracks is influenced by the degree of anisotropy. Additionally, cracks grow independently when the distance between cracks exceeds 12 m, and a planar propagation is observed for a distance above 20 m. The results also indicate that close cluster spacing leads to larger fractured area and resulting permeability. This work helps identify the optimal fracturing scenario for enhancing permeability in anisotropic unconventional reservoirs under different hydro-mechanical conditions.
GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES
(2022)
Article
Geochemistry & Geophysics
Yan Lu, Juan Li, Yuhui He, Lian-Feng Zhao, Jinhai Zhang
Summary: This study constructed the first Pn velocity and anisotropy model of the uppermost mantle in Central and Northwestern South America. The results showed significantly low Pn velocities and arc-parallel anisotropic structures beneath the volcanic arc in Central America. Furthermore, a separate, low Pn velocity was observed beneath a back-arc volcano in Nicaragua, indicating the separation of hot material upwelling in the uppermost mantle beneath this volcano from the main volcanic arc. Additionally, the stable Caribbean Plate exhibited high Pn velocities.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Energy & Fuels
Thormod E. Johansen, Jie Cao
Summary: A new theory for calculating fluid flow in laterally isotropic, spatially anisotropic permeable media is presented, which includes analytical models for well productivity in such media. The theory relies on a spatial volume preserving transform and provides closed formulas for directional permeabilities using different parameters than classical formulas. Both approaches are fully analytical and need to be proven identical.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2022)
Article
Geochemistry & Geophysics
Ping Tong
Summary: The study introduces a novel adjoint-state traveltime tomography method using P-wave traveltime data to determine velocity heterogeneity and azimuthal anisotropy simultaneously. The method was successfully applied to real data in central California, revealing structural anisotropy in the San Andreas Fault zone and stress-induced anisotropy off the fault zone.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Engineering, Multidisciplinary
Yang Zhao, Ronaldo Borja
Summary: This study introduces a continuum framework for simulating fluid flow through anisotropic elastoplastic media with double porosity. Effective stress measures are derived and a mixed finite element formulation is used to discretize the domain. Numerical simulations reproduce the hydromechanical response of Opalinus shale and demonstrate the efficacy of the stabilization scheme.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2021)