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Interpretation of geologic structures entails ambiguity and uncertainties. It usually requires interpreter judgment and is time consuming. Deep exploitation of resources challenges the accuracy and efficiency of geologic structure interpretation. The application of machine-learning algorithms to seismic interpretation can effectively solve these problems. We analyzed the theory and applicability of five machine-learning algorithms. Seismic forward modeling is a key connection between the model and seismic response, and it can obtain seismic data of known geologic structures. Based on the modeling data, we first optimized the seismic attributes sensitive to the target geologic structure and then we verified the accuracy of the five machine-learning algorithms by the cross-checking method. In this case, the random forest algorithm had the highest accuracy. So we examined the structural interpretation method based on a random forest using the 3D seismic reflection data from coalfield exploration. The prediction effect of this interpretation workflow is verified by comparison with known geologic structures on the plane and profile. The results suggest that the random forest algorithm is feasible to indicate geologic structure interpretations in the case of collapsed column and fault structures and it can effectively improve the efficiency of seismic interpretation and its accuracy. The machine-learning-based workflow provides a new technique for seismic structure interpretation in coal mining.

Separating weak diffractions in the prestack domain plays a vital role in high-resolution imaging small-scale discontinuities or inhomogeneities, which are associated with the migration paths and storage spaces for carbonate fracture-cave reservoirs. A shot-domain diffraction separation method is proposed with a SVMF (space-varying media filter) in the flattened shot domain. The diffractions with fast dynamic changings, including damping amplitudes and phase reversal, are filtered out by the spacing-varying median filter along the prediction-step directions of the flattened shot domain. The proposed method opens a possibility for separating diffractions in the shot domain and has an advantage in the traditional common-offset diffraction separation method. A numerical experiment illustrates the good performance of the proposed method in eliminating reflections and separating diffractions in the shot domain, and the field application further verifies its potential value in resolving the hidden small-scale cavities and tiny faults in carbonate reservoirs.

The conventional equation for 3D edge diffractions in the Cartesian coordinate system lacks angle information for studying the energy patterns in 3D seismic prestack data. Here, a new calculation method is presented for determining 3D edge-diffraction coefficients in a spherical coordinate system that can formulate the coefficients according to the azimuth and emergence angles. To avoid the singularity phenomenon, a Haar wavelet operator matrix is used for this new method. Analysis of the edge-diffraction coefficients variations with azimuth in the common-shot domain, common-receiver domain, and common-midpoint domain reveals that the variation curves of the coefficients can be used to identify the trend of a fault. The phenomenon of polarity reversal of the edge-diffraction coefficients is observed in the different domains, and the coefficients in the common-shot domain are more sensitive than in other domains.

The bulk density and bulk modulus of adsorbed coalbed methane are required to calculate the undrained bulk and shear moduli as well as the fluid-saturated density of the coal reservoir. We derived the formula for the bulk modulus and bulk density of adsorbed methane using the Langmuir equation for isothermal adsorption. The bulk density of adsorbed methane is positively correlated with the gas pressure and Langmuir volume, but it is negatively correlated with the Langmuir pressure and adsorbed methane saturation. The bulk density of adsorbed methane is greater than that of free-state methane for the same gas pressure. The bulk modulus of adsorbed methane is positively correlated with the gas pressure and negatively correlated with the Langmuir pressure; it is much larger than that of free methane, but it is still much smaller than that of water within the normal gas pressure range. Coal samples from the study area demonstrate that the water saturation is less than 95%. Considering adsorbed methane as a pseudosolid, calculations yield a very small difference in the bulk modulus of coal under room-dry conditions. Considering adsorbed methane as a gas, calculations based on spatially uniform or patchy saturation indicate that multiphase fluid saturation produces a very small difference in the elastic parameters and wave velocity of the fluid-saturated coal from the dual-phase fluid (water and free methane).

Solid oxide fuel cells cathode often suffers from degradation caused by water vapor in air. Here, we report a cathode material, La0.4Sr0.6Co0.2Fe0.7Nb0.1O3−δ (LSCFN), and evaluate its humidity tolerance by the characterization of the materials in wet air with different water vapor concentration at different temperature. The X-ray diffraction analysis indicates that the crystal structure of LSCFN is relatively stable in wet air with no observable impurity. However, a crystalline contraction is observed. Exposure of wet air to LSCFN causes the decrease of electrical conductivity and increase of polarization resistance because H2O might occupy the active sites for oxygen reduction reaction. For long-term operation, higher H2O concentration in air accelerates the degradation of LSCFN cathode.

In order to achieve the goal of ecological restoration, plant irrigation, and water retention in the external dump of open-pit coal mine in the arid desert area, it is proposed to use the mudstone in the stripped material to reconstruct the surface aquiclude and improve the water holding capacity of the topsoil. By taking the Hongshaquan Open-Pit Coal Mine as the study object, the red mudstone of mining level +650 was selected as the topsoil aquiclude material through the geological survey. XRD diffraction experiments are used to determine the composition of red mudstone including kaolinite mineral, quartz, potash feldspar, albite, and illite. The moisture content of the red mudstone is 4.16% as measured by the indoor drying experiment. And the particle size of 0.5 mm, 1 mm, and 2 mm and the thickness of 5 cm, 10 cm, and 20 cm rock samples were selected to conduct the indoor soil column experiment. Three indicators of initial infiltration rate, stable infiltration rate, and average infiltration rate were obtained according to the analysis and calculation of the water column drop rate, wet peak drop rate, and cumulative infiltration rate so that the permeability law and coefficient of each group of tests can be known. The finite element transient analysis theory and numerical simulation method were adopted to verify the results of physical experiments. The research results show that +650 level red mudstone has a strong antiseepage ability, and the smaller the particle size, the better the antiseepage performance. For 0.5 mm and 2 mm particle sizes, as the paving height increases, the water-proof effect is better. The laying height of 1 mm particle size has no obvious influence on the water barrier effect. The physical simulation was confirmed to have the same result trend as the numerical simulation, both of which are quadratic functions with the error within a reasonable range.

Author(s): Crawford, Emily D; Acosta, Irene; Ahyong, Vida; Anderson, Erika C; Arevalo, Shaun; Asarnow, Daniel; Axelrod, Shannon; Ayscue, Patrick; Azimi, Camillia S; Azumaya, Caleigh M; Bachl, Stefanie; Bachmutsky, Iris; Bhaduri, Aparna; Brown, Jeremy Bancroft; Batson, Joshua; Behnert, Astrid; Boileau, Ryan M; Bollam, Saumya R; Bonny, Alain R; Booth, David; Borja, Michael Jerico B; Brown, David; Buie, Bryan; Burnett, Cassandra E; Byrnes, Lauren E; Cabral, Katelyn A; Cabrera, Joana P; Caldera, Saharai; Canales, Gabriela; Castaneda, Gloria R; Chan, Agnes Protacio; Chang, Christopher R; Charles-Orszag, Arthur; Cheung, Carly; Chio, Unseng; Chow, Eric D; Citron, Y Rose; Cohen, Allison; Cohn, Lillian B; Chiu, Charles; Cole, Mitchel A; Conrad, Daniel N; Constantino, Angela; Cote, Andrew; Crayton-Hall, Tre'Jon; Darmanis, Spyros; Detweiler, Angela M; Dial, Rebekah L; Dong, Shen; Duarte, Elias M; Dynerman, David; Egger, Rebecca; Fanton, Alison; Frumm, Stacey M; Fu, Becky Xu Hua; Garcia, Valentina E; Garcia, Julie; Gladkova, Christina; Goldman, Miriam; Gomez-Sjoberg, Rafael; Gordon, M Grace; Grove, James CR; Gupta, Shweta; Haddjeri-Hopkins, Alexis; Hadley, Pierce; Haliburton, John; Hao, Samantha L; Hartoularos, George; Herrera, Nadia; Hilberg, Melissa; Ho, Kit Ying E; Hoppe, Nicholas; Hosseinzadeh, Shayan; Howard, Conor J; Hussmann, Jeffrey A; Hwang, Elizabeth; Ingebrigtsen, Danielle; Jackson, Julia R; Jowhar, Ziad M; Kain, Danielle; Kim, James YS; Kistler, Amy; Kreutzfeld, Oriana; Kulsuptrakul, Jessie; Kung, Andrew F

Coal seam gas (CSG) content is an important factor affecting the safety related to gas explosions, and it is also an indicator of natural gas resource assessment. The conventional method of establi...

With the increasing coal mining efficiency, the geological disaster sources in the mine serious threat production safety, Ground Penetrating Radar (GPR) is widely used for detecting those hidden disaster sources attributed to the advantage of high precision, but with detection distance limitation. We describe a novel GPR system for large-depth disaster detection in mine, which has the large-depth detection ability and the explosion-proof capability to adapt to the mine working environment. In comparison with the existing GPR systems, this novel system is improved with the following design features: the step acquisition accuracy of the host control unit is improved to be 2 ps; the split pluggable low frequency combined antenna realizes the impedance matching and improves the detection distance; a photoelectric conversion module is developed to guarantee 6000 m transmission distance for the high-frequency synchronization signal in mine. We carry out some experiments to validate the design, and the measurement results show that: the proposed GPR system can realize the fine exploration and the accurate identification; the maximum detection distance can be up to 80 m with reflection method and 300 m with transmission method under uniform geological conditions, which break the current detection distance limitations within 30 m, simultaneously, the detection accuracy can be up to 3 m. We expect that the proposed GPR system will be used for the large-depth geological disaster sources detection and provide an advanced approach for improving mining safety.

Ba0.9Co0.7Fe0.2Nb0.1O3−δ (BCFN), a promising cathode material for solid oxide fuel cells, demonstrates excellent activity to oxygen reduction reaction. However, under realistic operation conditions, cathode of cells often suffers from severe degradation due to the Cr deposition and poisoning from interconnects. In this work, effect of Cr deposition and poisoning on BCFN cathode has been investigated by various analysis techniques. Thereinto, temperature condition plays a significant role and BCFN demonstrate good stability at lower temperature (650 °C and 700 °C). However, polarization resistance of BCFN increases remarkably over 750 °C. According to the analysis, BaCrO4 are produced during the Cr deposition process, suppressing the oxygen reduction reaction on BCFN cathode.

Under realistic operation conditions of solid oxide fuel cells, CO2 and/or H2O in air can react with the cathode, and deteriorate its activity and stability. In this study, effects of CO2 and H2O on Ba0.9Co0.7Fe0.2Nb0.1O3−δ (BCFN) cathode have been studied by the analyses of X-ray diffraction patterns, electrical conductivity, and electrochemical impedance spectra. In simulated air with the co-existence of CO2 and H2O, BaCO3 is formed on the cathode surface at 600 °C, where BCFN is stable with either CO2 or H2O individually. In addition, BCFN performs lower electrical conductivity and higher polarization resistance (Rp) in air with CO2 and H2O. However, degradation of BCFN electrode is reversible: Rp of BCFN recovers when atmosphere is switched back to fresh air. Further, spray-drying method is proposed to fabricate Ce0.9Gd0.1O2−δ nano-particles coating on BCFN electrode, effectively improving the activity and stability of cathode against contamination of CO2 and H2O.

Factors such as the hydrogeological conditions, the lithological characteristics of the columns’ components, and the lithological characteristics and stress conditions of the coal seam roof and floor are interrelated and jointly affect column collapse. In this study, the disaster-causing mechanism of column collapse was studied. Based on the system theory, a collapsed column is divided into the column and the surrounding fissure zone as two subsystems for analysis. And, the permeability coefficient of the broken rock under different conditions was measured by a self-designed equipment. The variations of the permeability coefficient for rock samples with different particle diameters, different axial pressures Pa, and different seepage velocities were further studied. Through phenomena analysis and experimental data processing, it was concluded that, under the same pressure state, smaller particle diameter meant smaller permeability coefficient; with the increase of axial pressure, the permeability coefficient decreased; and the larger the water flow velocity was, the smaller the permeability coefficient became. For particle diameter Φ = 2.5–5 mm or larger, the tiny particles formed by randomly washing and breaking in the water flow blocked some of the channels. For particle diameters smaller than Φ = 2.5–5 mm, the smaller permeability coefficient was attributed to the turbulence resulting from non-Darcy flow. The study on the permeability of the fractured rock mass clarified the mechanism of water inrush from the fissure zone of the collapsed column: the collapsed column itself was impermeable, and the permeability of the fissure zone around the collapsed column was related to the lithological characteristics of the rock within the fissure zone and the sequencing of rock strata. When mining coal in areas with collapsed columns, experiments on collapsed columns and fissure zones are prerequisites. This study has a certain referential value for coal mining in this region.

It is important to study the mechanism of water inrush on a seam floor by exploring the rules of permeability variations during rock deformation on the seam floor and in the course of fracturing as well as their responses to characteristics of the macromechanical environment such as mine ground pressure, engineering geology, and fluid mechanics. First, through the analysis of bearing pressure changes in the process of exploiting the working face, a mechanical model for the seam floor above the confined water is established. Based on the graphic data-processing software Mathcad, the computational process and methods for assessing the vertical, horizontal, and shear stresses are provided together with the corresponding variation curve of the rock stratum 5 m below the floor, covering the entire process from a position 120 m away from the working face to a position 280 m behind it. Second, the permeability coefficients of different lithologies are measured in the laboratory. For rock stratum 5 m below the floor, the corresponding external loading path is set up according to its actual stress. The actual dynamic stress environment of the rocks is simulated, and their permeability characteristics are studied. In addition, based on data fitting, the permeability coefficient variations in the mining process are determined for a rock stratum 5 m below the floor. Finally, in accordance with the permeability variation law of the floor of the working face, the seam floor is divided into six areas, namely, the compression and expansion zone, the bed separation and expansion zone, the pressure relief zone, the compression zone, the stable recovery zone, and the stability zone. Thus, the water-resisting performance of the floor can be expressed more objectively.

For linear noise such as seismic ground roll, 3-D frequency-wavenumber-wavenumber (3-D FKK) domain filtering suppression is better than 2-D frequency-wavenumber (F-K) domain filtering. In recent years, with the continuous development of computer processing speed and memory capacity, high-density data acquisition in seismic exploration has been widely applied in the hydrocarbon industry, opening up the application of 3-D FKK filtering methods. We applied the 3-D FKK filtering software to a 3-D high-density onshore seismic field dataset from a coal mine in western China. The case study demonstrates that the linearity of the noise in the field data is better represented by constructing the single shot records as a minimum dataset. Both theoretical synthetic models and the 3-D high-density onshore seismic field data numerical filtering experiments demonstrate that the feasibility of 3-D FKK filtering.

Seismic diffractions contain valuable information regarding small-scale inhomogeneities or discontinuities, and therefore they can be used for seismic interpretation in the exploitation of hydrocarbon reservoirs. Velocity analysis is a necessary step for accurate imaging of these diffractions. A new method for diffraction velocity analysis and imaging is proposed that uses an improved adaptive minimum variance beamforming technique. This method incorporates the minimum variance, coherence factor, and correlation properties to improve the signal-to-noise ratio and enhance correlations. Our method can make seismic diffractions become better focused in semblance panels, allowing for the optimal migration velocity for diffractions to be accurately picked. Synthetic and field examples demonstrate that the migration velocity for the diffractions can differ from that for the reflections. The results suggest that the diffraction velocity analysis and imaging method is feasible for accurately locating and identifying small-scale discontinuities, which leads to the possibility of using this approach for practical application and seismic interpretation.

As a geochemical parameter for characterizing source rock in shale gas reservoirs, estimation of total organic carbon (TOC) is a main task of geophysical and geochemical studies. TOC can be used to evaluate the hydrocarbon generation potential of source rocks. Artificial intelligence (AI) methods have been proposed recently to obtain TOC from well logs. This avoids expensive and time-consuming core analysis of geochemical experiments. However, the optimal combination (selected) of logs should be determined to get the highest accuracy TOC. We used a well-trained least square support vector machine model to select appropriate well log inputs for intelligent model based on mean impact values. We used a conventional 9 logs obtained from a shale gas well in Tonghua Basin, China, to test our method. The results were compared with 215 TOC values from core analysis. In addition, we tested three AI of models, including artificial neural network based on backpropagation algorithm (ANN-BP), least square support vector machine (LSSVM), and particle swarm optimization-least square support vector machine (PSO-LSSVM). For these three models, both selected logs and all logs are used for comparison. The TOC results, obtained from different calculations, showed that selected logs significantly improved the TOC accuracy in each AI model. By comparing different AI model, we found that PSO-LSSVM model outperforms the other two models. The TOC obtained from the PSO-LSSVM can benchmark with core analysis results.

The localization of diffractors is a great challenge for seismic data with a low signal to noise ratio, and it is also difficult to preserve the polarity characteristics of edge diffracted waves in the separated diffractions. In this paper, we present a method to locate the diffraction points and extract the diffractions from reflected data by using the Hilbert transform, the modified apex-shifted Radon transform (ASRT) and double-branch Radon transform. The Hilbert transform is used to weaken the impact of dominant reflection amplitude on detecting weaker diffractions in instantaneous phase data. The modified ASRT and double-branch Radon transform are applied to locate the apex of diffractions and preserve the polarity reversal of edge diffracted waves emitted from reflector discontinuities, respectively. The synthetic and real data applications illustrate that the method not only accurately locate the diffraction apices but also discriminate the responses of the small-scale scattering objects and the reflector edges.

Three-dimensional seismic survey is widely applied, but 3-D filtering technology has yet to be fully utilized for the analysis of seismic field data. The common approach is to first filter inline and then crossline. However, an effective 3-D filtering method is expected to eliminate coherent noise, such as the ground roll. We propose a 3-D Butterworth filtering method in the time-space domain. Firstly, a Butterworth-type filter in the frequency-wavenumber-domain is designed to suppress the linear noise with a specific apparent velocity. Secondly, transforming this filter to the time and space domain yields 3-D partial differential equations (PDEs), which are applied to suppress the linear noise. Factorizing the finite-difference equations in a different direction other than decreasing the 3-D PDEs to 2-D PDEs produces a highly accurate and efficient algorithm. Designing the 3-D Butterworth filter, selecting the filtering parameters, and showing its application to synthetic data and a 3-D high-density onshore seismic field data from a region in western China are discussed in detail. Numerical experiments with 3-D high-density onshore seismic field data demonstrate that it is more effective than the 3-D frequency-wavenumber-wavenumber (FKK) filtering method.

Small-scale structures and tectonic stress are known to affect the production of coalbed methane. Ultrasonic borehole image logging (UBI) can be used to identify fractures and breakout zones around the wellbore and to analyze tectonic stress fields. In this study, a variety of image processing and automated fracture detection methods were used to process and interpret the ultrasonic logging data in a coal bed methane well. Combined with other logging data in the well, this study analyzed the ultrasonic logging response characteristics of the formation lithology and structure. Statistical analysis has been completed to identify the fracturing pattern. The results showed that the dip angle and orientation of the natural fracture were related to regional tectonics. The paleo-stress field, reflected by the natural fractures, was consistent with the geological conditions, while the current stress field, reflected by the breakout zones, was found to be different from the paleo-stress field. This study proposed a new method by using fractures with associated conjugate joints, which are obtained from UBI logs, to estimate the paleo-stress orientation.

Seismic diffractions are the responses of small-scale inhomogeneities or discontinuous geological features, which play a vital role in the exploitation and development of oil and gas reservoirs. However, diffractions are generally ignored and considered as interference noise in conventional data processing. In this paper, a new scheme for velocity analysis and imaging of seismic diffractions is proposed. Two steps compose of this scheme in our application. First, the plane-wave destruction method is used to separate diffractions from specular reflections in the prestack domain. Second, in order to accurately estimate migration velocity of the diffractions, the time-domain dip-angle gathers are derived from a Kirchhoff-based angle prestack time migration using separated diffractions. Diffraction events appear flat in the dip-angle gathers when imaged above the diffraction point with selected accurate migration velocity for diffractions. The selected migration velocity helps to produce the desired prestack imaging of diffractions. Synthetic and field examples are applied to test the validity of the new scheme. The diffraction imaging results indicate that the proposed scheme for velocity analysis and imaging of diffractions can provide more detailed information about small-scale geologic features for seismic interpretation.

Coal seam thickness is of great significance in mining coal resources. The focus of this study is to determine the relationship between coal seam thickness and seismic wave amplitude, and the factors influencing this relationship. We used a wedge model to analyze this relationship and its influencing factors. The results show that wave interference from the top and bottom interfaces is the primary reason for the linear relationship between seismic wave amplitude and wedge thickness, when the thickness of the wedge is less than one quarter of the wavelength. This relationship is influenced by the dominant frequency, reflection coefficients from the top and bottom boundaries, depth, thickness, and angle of the wedge. However, when the lateral shift between the reflected waves is smaller than the radius of the first Fresnel zone, the wedge angle and change in lithology at the top and bottom layers are considered to have little effect on the amplitude of the interference wave. The difference in the dominant frequency of seismic waves can be reduced by filtering, and the linear relationship between amplitude and coal thickness can be improved. Field data from Sihe coal mine was analyzed, and the error was found to be within 4% of the predicted seismic wave amplitude. The above conclusions could help predict the thickness of coal seam by seismic amplitude.

Seismic diffractions are the specific responses of small-scale inhomogeneities or discontinuous structures in the subsurface, such as faults and cracks, and can be used for locating reservoirs of oil and gas. However, because diffraction energy is much weaker than reflection energy, separating diffractions against the background of strong reflections from seismic data is difficult. In this paper, we propose a regularization method based on the l1-norm constraint to extract seismic diffractions from seismic records in the common-offset gathers. Regularization is a practical method for ill-posed nonlinear problems. The proposed method considers wavelet transform and l1-norm regularization in the plane-wave destruction method, which enhances the stability and accuracy of reflection local slopes. Wavelet transform has multi-level and multi-scale analysis properties and thus it is an effective method for sparse transform. Further, the l1-norm can effectively constrain sparsity properties. Through a synthetic example, the stability of this regularization method is demonstrated to be stronger than that of the conventional plane-wave destruction (PWD) method. Both the numerical simulation and field data application indicate that the proposed regularization method for diffraction extraction is promising and feasible in removing specular reflections and strengthening diffractions.

Potentiostatic operation of solid oxide electrolysis cells (SOECs) at the thermoneutral voltage enables operation of the SOECs close to 100% electrical efficiency and simplifies the heat management at the stack and system level. In this work, we investigate the long-term durability of Ni/yttria-stabilized zirconia (YSZ) fuel electrode supported SOECs operated for electrolysis of steam at the thermoneutral voltage of 1290 mV, by testing cells at 800, 750, and 700 ℃ for periods exceeding 1000 h each. The cells show different initial performance due to different operating temperatures, but all experience a significant degree of initial degradation within the first 300 h, with a degradation rate of 2.80, 1.93, and 1.77 A cm−2 kh−1 (~1.80, 1.51 and 1.90% kh−1) for the cells tested at 800, 750, and 700 ℃, respectively. Hereafter the cells show stable performance or even slight activation. After 300 h of operation, the cell tested at 750 ℃ exhibits performance comparable to the cell tested at 800 ℃ and more than 74% higher than the cell tested at 700 ℃, and this is maintained until the end of the test, suggesting that among three operating temperatures 750 ℃ is the optimum one. The different degradation behavior of the cells is further investigated by electrochemical impedance spectroscopy (EIS) analysis and post-test microstructural characterization. The cause of degradation is discussed in terms of electrode overpotential. Our findings highlight the significance of operating temperature optimization on the long-term durability of SOECs when operated in potentiostatic mode.

Solid oxide fuel cell (SOFC) stacks have complex multi-physics and multi-dimensional properties that are very difficult to observe in experiments. To solve this problem, a new modeling concept called alternative mapping is introduced in this paper. Using an artificial neural network (ANN), a multi-physics and multi-dimensional stack model can be decomposed into two bonded layers. Both can be solved much more rapidly and robustly than conventional models without losses in accuracy. A SOFC stack model is developed based on this concept. It is calibrated and validated by data from a single cell test and 30-layer stack experiments. The model is robust and rapid. The stack model results show that different physics and dimensional properties are closely related. Changes in each may cause chain reactions in the others, influencing the electrical efficiency or operation ranges. In this report, a fully 3D multi-physics and multi-dimensional dynamic simulation of a SOFC stack is implemented for the first time. Its dynamic behavior is a composite of electric-chemical reactions, gas transport, and heat transfer. These factors vary considerably in different positions and operational conditions.

CO2 geological storage is an effective way of reducing atmospheric CO2 concentration. The physical characteristics of the reservoir and the feasibility of CO2 flooding were analyzed based on the carbon capture, utilization, and storage (CCUS) project in Yanchang Oilfield, China. The heterogeneity of the reservoir indicates variation in the shape of the CO2 plume. A CO2 storage monitoring method based on a full convolutional neural network (FCN) that applies time-lapse difference seismic data is proposed for the geological task of CO2 storage monitoring. A total of 2800 sets of forward simulation time-lapse difference data and corresponding velocity changes were used to train the network. These data include noisy and noise-free data, which help improve the noise immunity of the network. The prediction accuracy of the network under different samples of training data, noise levels, and velocity changes is discussed. Furthermore, 100 sets of noisy data and 100 sets of noise-free data were used to verify the predictive ability of the network. The test results of the synthetic data show that the FCN-based CO2 storage monitoring method exhibits relatively high efficiency and high precision compared with time-lapse full waveform inversion.

With the incident P-wave, we derive approximate formulas for amplitudes and polarizations of waves reflected from and transmitted through a planar, horizontal boundary between an overlying isotropic medium and an underlying tilted transversely isotropic (TTI) medium assuming that the directions of the phase and group velocities are consistent. Provided that the velocities in the isotropic medium are equal to the velocities along the symmetry axis direction, we derive the relational expression between the propagation angle in the TTI medium and the propagation angle in the hypothetical isotropic medium, under the condition that the horizontal slowness is the same, and then we update the approximate formula of the polarization in the TTI medium. Provided that the slow and fast transverse waves (qS and SH) are generated simultaneously in the anisotropic interface, we linearize for a six-order Zoeppritz equation, derive the azimuthal formula of longitudinal and S-waves, and determine their detailed expressions within the symmetry axis plane. According to the derived azimuthal AVO formula, we establish medium models, compare the derived AVO with the precision, and obtain the following conclusions: (1) The dip angle for the symmetry axis with respect to the vertical may have a sufficiently large impact on AVO, and the vertical longitudinal wave can generate an S-wave. (2) For the derived AVO formula, within the symmetry axis plane, the fitting effect of the approximate and exact formulas is good; however, within the other incident planes, taking the azimuth angle 45° as an example, the approximation is suitable for the large impedance contrast if the anisotropic parameters are set properly. (3) The error between the approximation and precision is mainly caused by the difference between the reflected and transmitted angles, the velocities’ derivation with respect to azimuth, and the division of approximation into isotropic and anisotropic parts.

In this work, a water stable zirconium metal–organic framework functionalized with thiol groups was synthesized by a solvent-assisted ligand incorporation technique. The composites were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, specific surface area measurement and field emission scanning electron microscopy. The prepared material was then used as a novel adsorbent for Cu(II) removal from water. The experimental parameters associated with adsorption capability, such as the initial solution pH, contact time, and the presence of competing cations were investigated in detail. Under the optimal conditions, the adsorption follows a pseudo-second-order kinetics, and the equilibration time for the adsorption is 15 min. The Langmuir adsorption model was in better correlation with the isothermal adsorption data than the Freundlich model. The maximum Cu(II) adsorption capacity reached up to 42.70 mg g−1. Quantitative recovery of Cu(II) was achieved by using 0.1 mol L−1 HCl. The prepared adsorbent has fast adsorption efficiency, high adsorption capacity, and exceptional stability up to 50 adsorption/desorption cycles. It can be used as a promising candidate material for heavy metal ion removal and water treatment.

The diversity, composition and ecological guilds of soil fungal communities in relation to revegetation were assessed during an open-cast mining dump reclamation chronosequence of the soil

Novel flexible conductive ceramic films consisting of Cu1.5Mn1.5O4, Co3O4 and Al2O3 are developed for the cathode current collecting layer (CCCL) in solid oxide fuel cell (SOFC) stacks. These ceramic films are prepared by a water-based tape-casting method and sintered in situ at the operation temperature of intermediate temperature (IT)-SOFCs. The effects of addition amounts of Co3O4 and Al2O3 on the electrical conductivity of the CCCL and area specific resistance (ASR) of (La0.75Sr0.25)0.95MnO3-δ (LSM) cathode/the CCCL/SUS430 interconnect sandwich are studied. The results indicate that adding 3 wt.% of Co3O4 as sintering aids in Cu1.5Mn1.5O4 precursor powder can promote its sintering and thus reduce its contact resistance with neighboring components. Further combining Al2O3 as the binder with Cu1.5Mn1.5O4-3 wt.% Co3O4, though electrical conductivity of obtained materials decreases with the amount of Al2O3 addition increasing, the minimum ASR of 24.4 mΩ cm2 at 800 °C and a stable ASR of around 27 mΩ cm2 at 750 °C are achieved on LSM cathode/Cu1.5Mn1.5O4-3 wt.% Co3O4-10 wt.% Al2O3 CCCL/SUS430 interconnect sandwich. The developed flexible CCCL shows pronounced low contact resistance and high stability. Moreover, it can be easily cut and sintered in situ in SOFC stack, which is promising for the practical application in SOFC stacks.

This work demonstrates that a double perovskite Sr2Fe1.3Co0.2Mo0.5O6-δ (SFCM) with exsolved Co nanoparticles has enhanced the reaction activity and durability of solid oxide electrolysis cells (SOECs) for electrolysis of H2O, CO2 or CO2–H2O mixture. The Co nanoparticles are in situ exsolved from the parental SFCM in 10% H2–90% N2, as confirmed by analyses of XRD, XPS, TEM and SEM, and they can keep stable in the atmosphere of 50% CO2–50% H2 or 50% CO2–50% CO. The cells with a configuration of SFCM‖La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM)‖SFCM demonstrate excellent electrochemical performances in electrolysis. For example, polarization resistances of the electrolyzer are as low as 0.24 Ω cm2 in 50% H2O-50% H2 under open-circuit voltage. In addition, the cells for CO2/H2O co-electrolysis at 800 °C shows a reasonable durability at different current densities of 0.3, 0.6, 0.9, 1.2, 1.5, 1.8 A cm−2, and 1.0 A cm−2 for ~110 h s. Electrochemical impedance spectroscopy and distributed relaxation time analysis indicates that electrode surface exchange and diffusion are the rate-limiting steps in the electrolysis of CO2/H2O, and the resistances of these steps can be significantly decreased by the in situ exsolved Co nanoparticles from SFCM electrode, thereby providing higher activity and better stability.

Clarifying and locating small-scale discontinuities or inhomogeneities in the subsurface, such as faults and collapsed columns, plays a vital role in safe coal mining because these discontinuities or inhomogeneities may destroy the continuity of layers and result in dangerous mining accidents. Diffractions carry key information from these objects and therefore can be used for high-resolution imaging. However, diffracted/scattered waves are much weaker than reflected waves and consequently require separation before being imaged. We have developed a Mahalanobis-based diffraction imaging method by modifying the classic Kirchhoff formula with an exponential function to account for the dynamic differences between reflections and diffractions in the shot domain. The imaging method can automatically account for destroying of reflected waves, constructive stacking of diffracted waves, and strengthening of scattered waves. The method can overcome the difficulties in handling Fresnel apertures, and it is suitable for high-resolution imaging because of the consistency of the waveforms in the shot domain. Although the proposed method in principle requires a good migration velocity model for calculating elementary diffraction traveltimes, it is robust to an inaccurate migration velocity model. Two numerical experiments demonstrate the feasibility of the proposed method in removing reflections and highlighting diffractions, and one field application further confirms its efficiency in resolving masked faults and collapsed columns.

To study the impact of modern coal mining on the overlying formation, a full-lifecycle four-dimensional seismic monitoring study has been carried out. Four seismic data campaigns have been performed using flexi-bin geometry with square bins, with total duration of 171 days. The four seismic datasets have been processed with the same processing workflow and parameters; major problems such as statics correction, signal-to-noise ratio, resolution, and consistency processing are addressed taking into account the geological features of the research area. This guarantees that remaining four-dimensional differences between the time-lapse datasets show mostly geological factors due to the coal mining and effects such as surface subsidence. Our four-dimensional seismic monitoring of modern coal mining shows that mined and unmined areas have significant zoning characteristics; coal mining has a direct impact on the overlying formation. The mining leads to obvious event subsidence, which reflects that overlying formations undergo subsidence during the mining process. The overlying formation appears as two zones called caving zone and fractured zone. We determine the fault dip of the overlying formation at one end of the working face to be 56°or so by calculation and conversion. We also see that, during the coal mining process, over time, the overlying formation has a self-recovery capability, which gradually strengthens from the roof siltstone upward to the Aeolian sandstone near the surface. The stability of 20-m coal pillars between working faces displays a strengthening trend and remains safe during the mining process due to both coal seam supporting and formation compaction effects.

The methane adsorption at the surface of coal pores can induce coal swelling. Swelling strain is not only related to adsorption capacity but also equilibrium moisture content and coal ranks. The swelling strain in confined conditions will lead to the closure of coal reservoir cleat system, which reduces coal reservoir permeability, and further impedes free gas percolation. In this work, adsorption and strain experiments on two coal samples from China with vitrinite reflectance of about 1.64 and 3.68% were performed at 30, 40, and 50°C with the pressure of 15 MPa in the corresponding moisture state. The error is compared between measurement values and theoretical values. The results indicate that coal swelling is irreversible and anisotropic, and the methane adsorption capacity and swelling strain on two coal samples have a concave parabolic curve relationship with the increase in temperature. The effects of temperature on sorption and swelling on middle-rank coal is inferior to equilibrium moistur...

We consider sparsity-constraint inversion method for detecting seismic small-scale discontinuities, such as edges, faults and cavities, which provide rich information about petroleum reservoirs. However, where there is karstification and interference caused by macro-scale fault systems, these seismic small-scale discontinuities are hard to identify when using currently available discontinuity-detection methods. In the subsurface, these small-scale discontinuities are separately and sparsely distributed and their seismic responses occupy a very small part of seismic image. Considering these sparsity and non-smooth features, we propose an effective L 2-L 0 norm model for improvement of their resolution. First, we apply a low-order plane-wave destruction method to eliminate macro-scale smooth events. Then, based the residual data, we use a nonlinear structure-enhancing filter to build a L 2-L 0 norm model. In searching for its solution, an efficient and fast convergent penalty decomposition method is employed. The proposed method can achieve a significant improvement in enhancing seismic small-scale discontinuities. Numerical experiment and field data application demonstrate the effectiveness and feasibility of the proposed method in studying the relevant geology of these reservoirs.