Three-dimensional Heterogeneity Research Articles

Three-Dimensional Heterogeneity of the Pore and Fracture Development and Acoustic Emission Response Characteristics of Coal Rocks in the Yunnan Laochang Block

Studying the heterogeneity of coal reservoirs is significant to coal bed methane (CBM) exploitation. To investigate the development of the pore–fracture and acoustic emission response characteristics of the coal rock in the Yunnan Laochang block, four cores were extracted from the same coal rock in different directions. Through a comprehensive analysis using CT scanning and three-axis compression tests combined with synchronous acoustic emission experiments, a three-dimensional visualization of the pore–fracture structure and an analysis of the acoustic emission process during the elastic phase were conducted. Additionally, the impact of the heterogeneous development of pore–fractures on the acoustic emission characteristics was discussed. The results show that: there is strong heterogeneity in pore and fracture development within the coal rock, with the most significant development occurring along the direction of vertical stratification; the acoustic emission process in the elastic phase can be divided into three stages: strong–weak–strong; the development of pores and fractures affects the acoustic emission characteristics, with both counts and signal strength increasing as the percentage of voids rises; and the inferred in situ stress aligns with strike-slip faulting stress using acoustic emission. These results can provide a reference for the actual project.

Mapping three-dimensional intratumor proteomic heterogeneity in uterine serous carcinoma by multiregion microsampling.

Although uterine serous carcinoma (USC) represents a small proportion of all uterine cancer cases, patients with this aggressive subtype typically have high rates of chemotherapy resistance and disease recurrence that collectively result in a disproportionately high death rate. The goal of this study was to provide a deeper view of the tumor microenvironment of this poorly characterized uterine cancer variant through multi-region microsampling and quantitative proteomics. Tumor epithelium, tumor-involved stroma, and whole "bulk" tissue were harvested by laser microdissection (LMD) from spatially resolved levels from nine USC patient tumor specimens and underwent proteomic analysis by mass spectrometry and reverse phase protein arrays, as well as transcriptomic analysis by RNA-sequencing for one patient's tumor. LMD enriched cell subpopulations demonstrated varying degrees of relatedness, indicating substantial intratumor heterogeneity emphasizing the necessity for enrichment of cellular subpopulations prior to molecular analysis. Known prognostic biomarkers were quantified with stable levels in both LMD enriched tumor and stroma, which were shown to be highly variable in bulk tissue. These USC data were further used in a comparative analysis with a data generated from another serous gynecologic malignancy, high grade serous ovarian carcinoma, and have been added to our publicly available data analysis tool, the Heterogeneity Analysis Portal ( https://lmdomics.org/ ). Here we identified extensive three-dimensional heterogeneity within the USC tumor microenvironment, with disease-relevant biomarkers present in both the tumor and the stroma. These data underscore the critical need for upfront enrichment of cellular subpopulations from tissue specimens for spatial proteogenomic analysis.

What is the role of green ICT innovation in lowering carbon emissions in China? A provincial-level analysis

Green information and communication technology (ICT) is key to attaining carbon neutrality and a low-carbon economy. Applying panel data of 30 provinces in China, this study explores the internal mechanism and heterogeneous effect of green ICT innovation at lowering carbon emissions (CE) in China. The results disclose the following. Green ICT innovation significantly reduces the nation's provincial carbon emission, and the results remain valid after endogenous treatment and robustness test. Furthermore, green ICT innovation and CE do not exhibit a U-shape relationship, indicating the absence of a rebound effect. Green ICT innovation has an energy-saving effect and a productivity effect, demonstrating that energy intensity and green total factor productivity play an intermediary role. A better ICT development foundation strengthens green ICT innovation's carbon reduction effect. Besides, the CE reduction effect has three-dimensional heterogeneity depending on different economic development levels, type of green ICT innovation, and different carbon emissions regions. Finally, based on these results, the paper offers policy implications.

The impact of environmental uncertainty on ESG performance: Emotional vs. rational

This study analyzes the direct impact of environmental uncertainty on environmental, social, and governance (ESG) performance, while verifying the existence of a mediating path from an “emotional” and “rational” perspective. In addition, a three-dimensional heterogeneity analysis framework of “company-market-government” is established to explore the similarities and differences in the relationship between the two in different scenarios. The study finds that: (1) Environmental uncertainty reduces the ESG performance, and the conclusion remains valid after a series of robustness tests; (2) There is a mediating path between investor sentiment (i.e., “emotional”) and green innovation (i.e., “rational”) in the dampening effect of environmental uncertainty on corporate ESG performance, and green innovation has a masking effect on the direct impact; (3) In further analysis, the dampening effect of environmental uncertainty on ESG performance is more pronounced among companies in the “mature” stage and “small market, big government”. Facing the background of environmental uncertainty, this study enriches the mechanism of improving the corporate ESG performance, which is of practical significance to companies, markets, governments and other stakeholders.

Evaluation and Optimization of Heat Extraction Strategies Based on Deep Neural Network in the Enhanced Geothermal System

Production strategies and parameters control the efficiency of geothermal energy extraction related to the thermal stability and economic benefits of a geothermal system. The optimization strategies of geothermal energy extraction play a critical role in engineering and are generally determined through a numerical simulation approach. Considering the correlation among production parameters, numerical simulation requires numerous runs and manual adjustments, resulting in lower calculation efficiency and limited or local optimizations. This study proposes a high-efficiency network based on a three-dimensional heterogeneity model in the Gonghe Basin in China to achieve a high-efficiency and high-precision production strategy. The neural network was successfully established as a surrogate of the numerical model for the repetitive forward simulation. Meanwhile, the neural network is integrated with the Harris Hawks algorithm to optimize extraction strategies for sustainable heat extraction. This paper focuses on the effects of human-controlled operational parameters on geothermal systems. Results indicated that the maximum electrical power can be guaranteed 5.2 MW during a 50-year production period at an injection temperature of 60°C, an injection rate of 39 kg/s, and a well spacing of 380 m. The study provides important operational guidance for sustainable utilization in the Gonghe Basin. This simulation-optimization approach can be applied to other geothermal sites for sustainable energy production.

Three-dimensional heterogeneity in liquid electrolyte structures promotes Na ion transport and storage performance in Na-ion batteries.

Unlike solid materials, the molecular structure and chemical distribution in electrolyte solutions have been considered in isotropic states. Herein, we reveal controllable regulation of solution structures in electrolytes by manipulating solvent interactions for Na-ion batteries. Low-solvation fluorocarbons as diluents in concentrated phosphate electrolytes induce adjustable heterogeneity in electrolyte structures through variable intermolecular forces between high-solvation phosphate and diluents. An optimal trifluorotoluene (PhCF3) diluent weakens the solvation strength around Na+ and spontaneously leads to a locally enlarged Na+ concentration and global 3D continuous Na+ transport path thanks to the appropriate electrolyte heterogeneity. Besides, strong correlations between the solvation structure and the Na+ storage performance and interphases are demonstrated. PhCF3 diluted concentrated electrolyte enables superior operations of Na-ion batteries at both room temperature and a high temperature of 60 °C. A hard carbon anode exhibits a reversible capacity of 300 mA h g-1 at 0.2C and excellent life over 1200 cycles without decay.

Probing Heterogeneous Water Distributions within Fuel Cell Membranes Using Combined Neutron and X-Ray Tomography (NeXT)

Water management in a fuel cell is an essential prerequisite for achieving high cell performance, where sufficient water is required for membrane hydration while excess liquid water leads to undesired mass transport losses. Existing heterogeneity within the fuel cell, such as those created by flow-field lands and channels create three-dimensional (3-D) heterogeneity in water distribution within the fuel cell components, which may have long term effect on the durability of fuel cell components, such as the membrane (1). 3-D visualization techniques such as X-ray (1-4) and neutron (5) tomography are powerful in revealing the effect of the existing heterogeneity on water distributions in 3-D. However, there is an opportunity to combine neutron and X-ray tomography (6) to probe into the details of these heterogenous water distributions even further and clarify their impacts on 3-D membrane hydration. In this study, we investigate the effect of heterogeneity in fuel cells (primarily land-channel heterogeneity) on 3-D membrane hydration and membrane morphology changes during fuel cell operation using simultaneous neutron and X-ray tomography (NeXT). The fuel cell is tested at varying gas humidity conditions in a serpentine flow-field configuration. A simultaneous coupling of neutron and X-ray imaging provides high contrast across various components of the fuel cell. Specifically, neutrons are highly attenuated by hydrogen atoms; hence neutron imaging is used to accurately locate and quantify operando water distribution. X-rays are sensitive to metals; hence simultaneous X-rays imaging is used to track metal-containing components (metal flow-field) and interfaces (such as interface between Pt-containing catalyst layer and membrane). This study demonstrates how heterogeneity in fuel cells plays a role in 3-D membrane hydration and needs to be tailored to enhance cell performance. References Y. Singh, R. T. White, M. Najm, T. Haddow, V. Pan, F. P. Orfino, M. Dutta, and E. Kjeang, J. Power Sources., 412 (2019): 224-237. Y. Nagai, J. Eller, T. Hatanaka, S. Yamaguchi, S. Kato, A. Kato, F. Marone, H. Xu and F. N. Büchi, J. Power Sources., 435 (2019). S. J. Normile, D. C. Sabarirajan, O. Calzada, V. De Andrade, X. Xiao, P. Mandal, D. Y. Parkinson, A. Serov, P. Atanassov and I. V. Zenyuk, Meter. Today Energy., 9 (2018). S. S. Alrwashdeh, I. Manke, H. Markötter, M. Klages, M. Göbel, J. Haußmann, J. Scholta and J. Banhart, ACS Nano., 11, 6 (2017). J. M. LaManna, Y. Yue, T. A. Trabold, J. D. Fairweather, D. S. Hussey, E. Baltic and D. L. Jacobson, Meet. Abstr. - Electrochem. Soc., 32 (2017). J. M. LaManna, D. S. Hussey, E. Baltic and D. L. Jacobson, Rev. Sci. Instrum., 88, 11 (2017).

Tectonics and Geodynamics of the Cascadia Subduction Zone

The Cascadia subduction zone, where the young and thin oceanic Juan de Fuca plate sinks beneath western North America, represents a thermally hot endmember of global subduction systems. Cascadia exhibits complex and three-dimensional heterogeneities including variable coupling between the overriding and downgoing plates, the amount of water carried within and released by the oceanic plate, flow patterns within the mantle wedge and backarc, and the continuity and depth extent of the subducting slab. While recent research has benefitted from extensive onshore and offshore deployments of geophysical instrumentation, a consensus on many important aspects of Cascadia’s magmatic, tectonic, and geodynamic setting remains elusive.

Moment Tensor Solutions for Earthquakes in the Southern Korean Peninsula Using Three-Dimensional Seismic Waveform Simulations

Precise estimates of earthquake source properties are crucial for understanding earthquake processes and assessing seismic hazards. Seismic waveforms can be affected not only by individual event properties, but from the Earth’s interior heterogeneity. Therefore, for accurate constraints on earthquake source parameters, the effects of three-dimensional (3D) velocity heterogeneity on seismic wave propagation need evaluation. In this study, regional moment tensor solutions for earthquakes around the southern Korean Peninsula were constrained based on the spectral-element moment tensor inversion method using a recently developed high-resolution regional 3D velocity model with accurate high-frequency waveform simulations. Located at the eastern margin of the Eurasian plate, the Korean Peninsula consists of complex geological units surrounded by thick sedimentary basins in oceanic areas. It exhibits large lateral variations in crustal thickness (> 10 km) and seismic velocity (>10% dlnVs) at its margins in the 3D model. Seismic waveforms were analyzed from regional earthquakes with local magnitudes > 3.4 that occurred within and around the peninsula recorded by local broadband arrays. Moment tensor components were inverted together with event locations using the numerically calculated Fréchet derivatives of each parameter at periods ≥ 6 s. The newly determined solutions were compared with the results calculated from the one-dimensional (1D) regional velocity model, revealing a significant increase in a double-couple component of > 20% for earthquakes off of the coastal margins. Further, compared to initial solutions, ≤ 5 km change in depth was observed for earthquakes near the continental margin and sedimentary basins. The combination of a detailed 3D crustal model and accurate waveform simulations led to an improved fit between data and synthetic seismograms. Accordingly, the present results provide the first confirmation of the effectiveness of using 3D velocity structures for accurately constraining earthquake source parameters and the resulting seismic wave propagation in this region. We suggest that accurate 3D wave simulations, together with improved source mechanisms, can contribute a reliable assessment of seismic hazards in regions with complex continental margin structures and sedimentary basins from offshore earthquakes whose seismic waveforms can be largely affected by 3D velocity structures.

Hydro-thermo-chemo-mechanical modeling of carbon dioxide injection in fluvial heterogeneous aquifers

Understanding geological sequestration of carbon dioxide (CO2) requires fully-coupled simulation of thermal-hydrological-mechanical-chemical (THMC) processes within well-characterized subsurface heterogeneity. A CO2 injection pilot project was performed in the Cranfield site, Mississippi, USA, where subsurface heterogeneity reflects fluvial deposition. During the project, CO2 was injected through an injection well and was monitored using two observation wells. We incorporate high-resolution three-dimensional heterogeneity model of the site into multiphase and multi-component flow and transport models. We validate our models and evaluate how bottom-hole pressure (BHP) in injection well, CO2 breakthrough times at observation wells, and efficiency of trapping mechanisms (i.e., dissolution, snap-off trapping, mobile CO2) are controlled by (1) non-isothermal CO2 injection, (2) geochemical reactions, (3) capillary pressure heterogeneity, (4) geomechanical effects, and (5) permeability enhancement close to the injection well. Results suggest that neglecting thermal effects lowers BHP, shortens breakthrough times, overestimates dissolution, and underestimates snap-off trapping. The BHP remains unchanged, breakthrough times are overestimated, and solubility and snap-off trapping are underestimated when geochemical reactions are ignored. Ignoring capillary pressure heterogeneity results in underestimation of BHP and dissolution and overestimation of breakthrough times. Ignoring geomechanical process results in lower BHP, shorter breakthrough times, increased dissolution, and decreased snap-off trapping. Ignoring permeability enhancement results in underestimation of breakthrough times and solubility trapping, and overestimation of snap-off trapping. Our results have important practical implication for designing effective field scale experiments and numerical simulations of geological carbon sequestration. Other multiphase flow problems in which subsurface heterogeneities are the main controlling factor (e.g., hydrogen storage) may benefit from this work.

Quantitative prediction of the drilling azimuth of horizontal wells in fractured tight sandstone based on reservoir geomechanics in the Ordos Basin, central China

Hydraulic fracturing and horizontal well technology can effectively improve reservoir production but can affect reservoir reconstruction through many factors, including the reservoir lithology, reservoir stress state and natural fractures. Considering tight sandstone as an example, the finite element method (FEM) and the optimal trajectory design scheme for a horizontal well are used in this study to determine the influence of the stress state, mechanical parameters and natural fractures of rock on the effects of hydraulic fracturing. Core reorientation via a paleomagnetic method is used to determine the natural fracture orientations in different well blocks. The in-situ stress magnitudes and directions are determined using microseismic monitoring of hydraulic fracturing, borehole breakout analysis, difference strain analysis and acoustic emission experiments. A heterogeneous geomechanical model is formulated based on log interpretations of the rock mechanical parameters of 111 wells and the results of triaxial mechanical experiments. The FEM is used to determine the in-situ stress field in the Dongrengou block. A predictive model for the hydraulic fracture propagation direction is formulated considering the in-situ stress, geomechanical model and natural fracture orientation. The results show that the mechanical parameters of the Dongrengou block are characterized by planar anisotropy and three-dimensional heterogeneity, where the rock mechanical parameters vary considerably across the plane and are vertically stratified. Using these results in conjunction with the drilling directions and oil production of 14 horizontal wells shows that oil and gas recovery is maximized by orienting horizontal wells perpendicular to the propagation direction of hydraulic fractures.

Three-Dimensional Heterogeneity of Cerebellar Interposed Nucleus-Recipient Zones in the Thalamic Nuclei

The cerebellum is conceptualized as a processor of complex movements and is also endowed with roles in cognitive and emotional behaviors. Although the axons of deep cerebellar nuclei are known to project to primary thalamic nuclei, macroscopic investigation of the characteristics of these projections, such as the spatial distribution of recipient zones, is lacking. Here, we studied the output of the cerebellar interposed nucleus (IpN) to the ventrolateral (VL) and centrolateral (CL) thalamic nuclei using electrophysiological recording in vivo and trans-synaptic viral tracing. We found that IpN stimulation induced mono-synaptic evoked potentials (EPs) in the VL but not the CL region. Furthermore, both the EPs induced by the IpN and the innervation of IpN projections displayed substantial heterogeneity across the VL region in three-dimensional space. These findings indicate that the recipient zones of IpN inputs vary between and within thalamic nuclei and may differentially control thalamo-cortical networks.

Fiber Optic Pressure Measurements Open Up New Experimental Possibilities in Hydrogeology.

Fiber-optic (FO) technology is being used increasingly for measurement methods in a variety of environmental applications. However, FO pressure transducers are rarely used in hydrogeological applications. We review the current state of Fabry-Pérot interferometry-based FO pressure transducers, including their advantages and limitations, as another option for high-resolution pressure- or head-change measurements in conventional or advanced aquifer testing. Resolution and precision specifications of FO transducers meet or exceed commonly used non-FO pressure transducers. Due to their design, FO transducers can be used in small-diameter (inner diameter ≥1/4inch) and continuous multichannel tubing (CMT), sampling points, multilevel packer systems, and Direct Push-based in situ installations and testing. The small diameter of FO transducers provides logistical advantages-especially for tests with monitoring at many zones in a number of wells and/or CMTs (e.g., no reels, placement just below water level in access tubes vs. within isolated zones, reduced weight and volume, small footprint at single point of data acquisition). Principal limitations are small measurement drift that may become evident for tests longer than a few hours, and higher-than-average cost. We present field examples of FO transducer performance in short-term tests with high consistency of acquired data and higher resolution (i.e., capturing significant hydrologic information) compared with commonly used non-FO transducers. Given the above, including advantageous logistical features, FO transducers can open new experimental possibilities in areas of high-resolution three-dimensional (3D) heterogeneity (flow and transport, remediation, critical zones); 3D fracture networks and fundamental hydromechanical behavior; complex 3D flow and leak detection (mines, dams, repositories, geothermal systems).

Identification of plastic constitutive Johnson–Cook model parameters by optimization-based inverse method

Abstract Because the design of most products incorporates numerical analysis such as the finite element method, these days, accurate determination of dynamic material model parameters is significant. Usually, the dynamic constitutive model parameters such as those in the Johnson–Cook (JC) model are determined by fitting stress–strain curves obtained by split Hopkins pressure bar (SHPB) tests at various strain rates and temperatures. However, the determination of model parameters by fitting cannot consider potential three-dimensional heterogeneities of stress propagation because the stress and strain are calculated with the assumption of one-dimensional wave propagation. In this study, to accurately determine plastic constitutive model parameters considering all of the potential heterogeneities of stress propagation, an optimization-based inverse method was proposed. Multiple objectives were defined with multiple experimental data that were obtained by SHPB tests at different conditions. The error was defined using transmitted and reflected bar signals obtained in experiments and finite element analysis with candidate model parameters. JC model parameters were set as design variables and determined to minimize the error. To show the reliability of the proposed method, experimental data were generated numerically by FE analysis with known model parameters. The parameters determined by the proposed method were compared with the known exact values. Model coefficients were also determined by fitting the stress–strain relations to show the superiority of the proposed method. Though the fitting of stress–strain curves can also reasonably determine the model coefficients, it was shown that the model parameters could be determined accurately by the proposed optimization-based inverse method.

Research on the forward modeling of controlled-source audio-frequency magnetotelluric in three-dimensional electrical conductivity and magnetic permeability heterogeneity media

We have developed a three-dimensional (3-D) algorithm for computing the controlled-source audio-frequency magnetotelluric response which is capable of handling local inhomogeneities in the electrical conductivity and magnetic permeability distribution. It is a difference equation algorithm that is based on the integral forms of Maxwell’s equations. To avoid a spatial singularity being introduced by the source, we used a secondary electric field approach. We adopt a staggered-grid finite difference method to disperse the secondary electric field equation which is simple to realize and can calculate relatively complex models. The final sparse equation system after dispersion is solved using an ILU preconditioning quasi-minimal residual (QMR) method. The code is validated for nonmagnetic and permeable conductive structures by two synthetic models. One of them is a two-dimensional (2-D) nonmagnetic conductive geoelectric model; we validate our 3-D computation result by comparing it to the result of 2-D CSEM finite element forward program. The other one is a 3-D permeable geoelectric model; we validate our 3-D computation result by using the COMSOL Multiphysics software. We also designed two theoretical 3-D geoelectrical models to analyze the effects of magnetic permeability heterogeneity. Numerical simulation results well reveal the influence of magnetic permeability heterogeneity on high-resistance and low-resistance models.

Three-dimensional heterogeneity analysis of climate aid's carbon reduction effect

Exploring the effectiveness of climate aid is crucial to distribute funds scientifically and maximize its impact. A body of related literature has estimated the impact of international climate aid on carbon emissions. However, these studies did not adequately consider the multi-dimensional heterogeneity of climate aid's carbon reduction effect. Based on national panel data of 77 recipients from 1980 to 2016, this study is the first to analyze the heterogeneous characteristics of climate aid's carbon reduction effect from three dimensions of emission level, aid level, and income level. Results show that, totally speaking, climate aid has a significant negative effect on carbon emissions in recipient countries. From the perspective of heterogeneity, climate aid has significant reduction effects for the recipient countries with middle-emission level. Meanwhile, climate aid also has significant negative effects on carbon emissions in recipient countries with high-aid level, i.e., only when the amount of aid reaches relatively high levels can climate aid play its role in reducing emissions. Furthermore, climate aid only conducts a significant reduction effect for middle-income recipients. This study recommends proposing a new collective quantified financial target, pursuing low-carbon economic development, optimizing the aid distribution, and enhancing capacity building to maximize the effectiveness of climate aid.

A Heterogeneity Radiomic Nomogram for Preoperative Differentiation of Primary Gastric Lymphoma From Borrmann Type IV Gastric Cancer.

This study aimed to preoperatively differentiate primary gastric lymphoma from Borrmann type IV gastric cancer by heterogeneity nomogram based on routine contrast-enhanced computed tomographic images. We enrolled 189 patients from 2 hospitals (90 in the training cohort and 99 in the validation cohort). Subjective findings, including high-enhanced mucosal sign, high-enhanced serosa sign, nodular or an irregular outer layer of the gastric wall, and perigastric fat infiltration, were assessed to construct a subjective finding model. A deep learning model was developed to segment tumor areas, from which 1680 three-dimensional heterogeneity radiomic parameters, including first-order entropy, second-order entropy, and texture complexity, were extracted to build a heterogeneity signature by least absolute shrinkage and selection operator logistic regression. A nomogram that integrates heterogeneity signature and subjective findings was developed by multivariate logistic regression. The diagnostic performance of the nomogram was assessed by discrimination and clinical usefulness. High-enhanced serosa sign and nodular or an irregular outer layer of the gastric wall were identified as independent predictors for building the subjective finding model. High-enhanced serosa sign and heterogeneity signature were significant predictors for differentiating the 2 groups (all, P < 0.05). The area under the curve with heterogeneity nomogram was 0.932 (95% confidence interval, 0.863-0.973) in the validation cohort. Decision curve analysis and stratified analysis confirmed the clinical utility of the heterogeneity nomogram. The proposed heterogeneity radiomic nomogram on contrast-enhanced computed tomographic images may help differentiate primary gastric lymphoma from Borrmann type IV gastric cancer preoperatively.

The origin of secondary microseism Love waves

The interaction of ocean surface waves produces pressure fluctuations at the seafloor capable of generating seismic waves in the solid Earth. The accepted mechanism satisfactorily explains secondary microseisms of the Rayleigh type, but it does not justify the presence of transversely polarized Love waves, nevertheless widely observed. An explanation for two-thirds of the worldwide ambient wave field has been wanting for over a century. Using numerical simulations of global-scale seismic wave propagation at unprecedented high frequency, here we explain the origin of secondary microseism Love waves. A small fraction of those is generated by boundary force-splitting at bathymetric inclines, but the majority is generated by the interaction of the seismic wave field with three-dimensional heterogeneity within the Earth. We present evidence for an ergodic model that explains observed seismic wave partitioning, a requirement for full-wave field ambient-noise tomography to account for realistic source distributions.

Rock Fracture Monitoring Based on High-Precision Microseismic Event Location Using 3D Multiscale Waveform Inversion

Microseismic (MS) source location can help us obtain the fracture characteristics of a rock mass under a thermal-hydraulic-mechanical (THM) coupling environment. However, the commonly used ray-tracing-based location methods are easily affected by the large picking errors, multipath effects of travel time, and focusing and defocusing effects of rays in wavefield propagation, which are caused by the strong three-dimensional (3D) heterogeneity in mining areas. In this paper, we will introduce the rapidly developed waveform inversion-based location method into a mine MS field study. On this basis, the wavefields were modeled by utilizing a high-resolution 3D velocity model, a fractional-order Gaussian wavelet source-time function, and spectral element method (SEM) wavefield modeling. In order to reduce the computation cost of wavefield modeling, the 3D ray-shooting method based on a coarse grid was adopted to obtain an approximate MS event location. Based on this initial location, the multiscale waveform inversion strategy (from coarse to fine grids) and the L-BFGS iteration optimization algorithm were separately jointly selected to improve wavefield modeling speed efficiency and iterative convergence rate. Then, the IMS MS monitoring system set in the Yongshaba mine (China) and its tomographic 3D velocity model were used to conduct the synthetic test and application study. Results show that the source-time function based on the fractional-order Gaussian function wavelet can better fit complex recording waveforms compared with the conventional Ricker wavelet-based source-time function, and the waveform misfit during the L-BFGS iteration decreased rapidly. Furthermore, the multiscale waveform inversion method can obtain a similar location accuracy compared with the waveform inversion based on a single fine grid, and it can significantly decrease the iteration times and wavefield modeling computational cost. The average location error of the eight premeasured blasting events by the proposed approach is only 17.6 m, which can provide a good data research basis for analyzing MS event location and rock mass fracture characteristics in a mine.

Geological structure, geomechanical perturbations, and variability in hydraulic fracturing performance at the scale of a square mile

Wellbore-centric Earth models generally rely on one-dimensional assumptions (flat layers, laterally uniform properties, etc.). This is mostly due to a lack of means to resolve three-dimensional heterogeneities away from the well — core and log data lack depth of investigation while seismic imaging resolution is often no better than a few tens of meters laterally. In this paper, we used case examples from the Fayetteville, Niobrara and Marcellus US shale plays to demonstrate how borehole structural geology, based on borehole-wall images alone, allows to document the geological structure in 3D (faults and natural fractures included) with high resolution, up to tens to hundreds of meters away from the well — a dimension characteristic of hydraulic fractures. We investigated on those examples whether 1D assumptions were violated. In all three cases, structural features (folding and faulting) were observed with amplitudes up to tens of meters, though below seismic resolution. Borehole-wall images further provided information on natural fracture orientation and distribution, which enabled discrete fracture network modeling. Thanks to the 3D nature of the structural model, the effects of the structure, rock mass anisotropy and heterogeneity, were better accounted for when modeling geomechanical conditions. Well log and core data were positioned more accurately with respect to the layers and lateral variability in both material properties and pressure was therefore better assessed. Moreover, faults and natural fractures were accounted for. All of these effects were observed to be significant on the stress field along layers, across fault blocks, and at discontinuities, including significant stress rotations and substantial effects in stress magnitudes. We finally show how horizontal well placement and hydraulic fracturing are sensitive to such 3D effects. We conclude that, at the scale of a square mile, the Earth is not everywhere flat and that Earth models no longer need to be.