Seismic Tests Research Articles

Quantitative characterization and application of deep learning carbonate reservoir

Abstract Quantitative reservoir characterization is an important research task in carbonate reservoir development. At present, the comprehensive evaluation of drilling, logging, seismic, and productivity testing data is usually used, which requires a large number of test data and tedious manual data collation. Deep learning technology can independently learn complex reservoir characteristics, has a strong ability for high-dimensional data structure mining, and has a strong advantage in solving complex nonlinear reservoir description problems closely related to various geological characteristics. Therefore, this paper applies deep learning technology to reservoir characterization. First, a deep neural network model is constructed, and then seven characteristic parameters such as fracture density, fracture opening, fracture porosity, matrix porosity, total porosity, effective thickness, and specific oil production index are taken as input variables. After model training and verification, the effective permeability distribution map of the reservoir in the target area can be automatically generated. The results show that the deep learning method has strong adaptability and practicability for the quantitative characterization of complex reservoirs, and provides a new way of thinking for the quantitative characterization of reservoirs.

Seismic testing and fragility analysis considering material strength uncertainty of 1100 kV GFRP composite power transformer bushing

Nowadays glass-fibre reinforced polymer (GFRP) composite insulators are widely employed in electrical equipment in substations. However, there is a scarcity of reports on seismic qualification of transformer bushings that adopt GFRP insulators. Thereby, this case implements shaking table tests on a 1100 kV GFRP composite power transformer bushing. The study analyses the acceleration responses and dynamic amplification effects, as well as the strain responses. The combined stresses at the vulnerable positions are computed to authenticate the seismic performance. Using a simulation model, the seismic fragility of the transformer bushing considering the material strength uncertainty is assessed and discussed. The results indicate that the GFRP composite bushing meets the requirements of the relevant code and its seismic performance is qualified under an artificial ground motion with PGAs of 0.6 g and 0.8 g. For a given factor of safety of 1.67, the bushing can sustain 0.4 g earthquakes with a failure probability near 0 and 0.8 g earthquakes with a failure probability<50 %. Controlling coefficient of variation of the GFRP material strengths is beneficial to decreasing seismic fragility of the transformer bushing within a specific PGA range. Weibull and Normal distributions for fitting the strength distributions of the GFRP materials have different impacts on the seismic fragility of the bushing, which should be given more attention in seismic design.

Susceptibility to Liquefaction of Iron Ore Tailings in Upstream Dams Considering Drainage Conditions Based on Seismic Piezocone Tests

One of the critical challenges facing the mining sector is related to the prevention and mitigation of catastrophic incidents associated with its tailing dams. As mining tailings are very heterogeneous and field characterization is expensive and complex, geotechnical properties of these materials are largely unknown. The seismic cone penetration test (SCPTu) provides a field approach to estimate a large array of geotechnical information, including the liquefaction potential of tailing dams. Yet, the exploration of strain softening behaviors in geomaterials under undrained loading, utilizing the state parameter (ψ) inferred from SCPTu tests initially applied to soft soils, has been often used for mining tailings. This study is concerned with the implementation of a tailing classification system which uses the ratio between the small strain shear modulus and the cone tip resistance (G0/qt). A series of laboratory tests was executed, and three different methodologies were adopted to assess the effects of (partial) drainage conditions based on 531.26 m of SCPTu measurements conducted at three different upstream iron ore tailing dams in Brazil. Furthermore, the G0/qt ratio is integrated with ψ to assess the liquefaction tendencies of the investigated materials. The findings reveal the heterogeneous nature of the tailings, wherein indications of partial drainage are discernible across numerous records. Liquefaction analyses demonstrate that the tailings exhibit a contractive behavior in over 94% of the SCPTu data, confirming their susceptibility to flow liquefaction. Our findings are relevant for site characterization within iron ore tailing dams and other mining sites with similar geotechnical attributes.

Cyclic performance of precast hollow core slab to beam connections using innovative assembling technique

This study emphasizes the performance of novel assembling technique using anchored continuity bars as a connection detail between precast hollow core slab and beam, aiming to achieve faster assembly and increased efficiency. The study further conducts a detailed analysis of core rebar impact on the hollow core slab to beam connection, examining both the assembly technique and core rebar influence. Effectiveness assessment of newly introduced anchored continuity bars and core rebars utilized five full scale half span prototypes under reverse cyclic loading. Findings indicate that connections incorporating anchored continuity and core rebar exhibit high strength, less stiffness deterioration, high ductility, and substantial energy dissipation, thereby meeting seismic load requirements. All connections met ACI 374.1–05 criteria, demonstrating satisfactory performance in seismic tests concerning relative energy dissipation ratio and stiffness ratio criteria. Notably, the continuity bar anchored to beam reinforcement-core reinforcement anchored to beam with ties connection surpasses the continuity bar anchored to beam reinforcement connection, demonstrates a superior average peak load carrying capacity of 149.8 % and cumulative energy dissipation of 288.78 %. The study concluded that the innovative assembly using anchored continuity bar with the inclusion of core rebar in the voids contributes to the improvement of connection performance under positive drift moment capacity and partly enhances negative drift moment capacity, thereby enhancing the overall stability of floor units in the event of seat loss.

Seismic Performance of Drop-In Anchors in Concrete under Shear and Tension

This paper presents an experimental study conducted on the behavior of drop-in anchors in uncracked concrete slabs. Both seismic (cyclic) load tests and static load tests to collapse are performed on drop-in anchors subjected to tension or shear forces. Three different anchor sizes are subjected to seismic qualification testing, followed by a static load test to collapse. The test results confirm the capability of the tested anchors to sustain simulated pulsating seismic tension and shear loading with frequency ranges between 0.1 and 2.0 Hz. It was observed that no tension failure occurred at the end of the cyclic load tests for all the tested anchors, and their residual inelastic maximum displacement at the end of the cyclic tension test was relatively small. Moreover, the experimental results show that the anchors’ ultimate capacities are higher than those specified by the anchor manufacturer. Finally, the anchors’ experimental pullout shear capacities are compared with the failure prediction equations in the literature and design codes. It is found that the theoretical models provide a conservative prediction of the concrete breakout of anchors in tension compared to the experimental ultimate loads. The coefficient for pry-out strength (kcp) equal to 2 or slightly smaller than 2 is likely to predict a better pry-out capacity with the experimental results compared to the application of the high conservative value of kcp equal to 1, as given in the code.

A multi-orientation system for characterizing microstructure changes and mechanical responses of fine-grained gassy sediments associated with gas hydrates.

Fine-grained marine sediments containing veiny and nodular gas hydrates will evolve into fine-grained gassy sediments after hydrate dissociation due to climate-driven ocean warming. The mechanical properties of the fine-grained gassy sediments are basically acquired by ocean engineering design. However, they have not been fully understood, largely due to the lack of microstructure visualization. In this paper, a new system is developed to jointly conduct x-ray computed tomography scans, oedometer tests, and seismic wave testing on a single specimen with temperature being well controlled, allowing varieties of experimental data to be acquired effectively and automatically. The results show that stress history can hardly affect the undrained stiffness of fine-grained gassy sediments, while the drained stiffness of fine-grained sediments without gas bubbles is stress history dependent. After being unloaded, many microstructure changes remain, and examples include the free gas distribution being more concentrated and the connectivity among gas bubbles becoming much better. The multi-orientation system lays the foundation for further studies on the microstructure changes and mechanical responses of fine-grained gassy sediments associated with gas hydrates.

Determination of Constrained Modulus of Granular Soil from In Situ Tests—Part 2 Application

The paper demonstrates how the concepts presented in the companion paper: “Determination of Constrained Modulus of Granular Soil from In Situ Tests—Part 1 Analyses” can be applied in practice. A settlement design based on the tangent modulus method is described. Extensive in situ tests were performed on a well-documented test site consisting of sand with silt and clay layers. The field tests comprised different types of penetration tests, such as the cone penetration test, the flat dilatometer, and the seismic down-hole test. The modulus number and the constrained tangent modulus were derived from the cone penetration test with pore water pressure measurement and the flat dilatometer test. In addition, the shear wave speed was determined from two seismic down-hole tests, from which the small-strain shear modulus could be evaluated. The constrained modulus obtained from the cone penetration test with pore water pressure measurement (CPTU) and the flat dilatometer (DMT) was compared with that from the seismic down-hole tests. The importance of the stress history on the constrained modulus was demonstrated. The range of modulus numbers, derived from different in situ tests, compares favorably with empirical values reported in the literature.

Innovative graph-based video processing methodology for collapse early warning of historic masonry buildings

In the present study an innovative video processing methodology is proposed for application to vibration data of historic masonry structures. The proposed methodology is based on graph theory and topology analysis applied to magnified videos in search of effective parameters for early-warning signals before the collapse of structures in case of earthquakes. The proposed method was validated through seismic tests of a brick-masonry mockup representing a vault of the mosque in the Palace of the Dey, Algiers. In particular, the seismic tests were carried out at increasing earthquake intensity up to the final collapse of the mockup. After processing the videos of the seismic tests by motion magnification method, the magnified video frames were transformed into a graph of the structure. Finally, several graph indices were calculated and monitored during the vibration. The monitored parameters were analyzed in search of potential threshold values suitable to generate an early warning signal. In particular, the inverse algebraic connectivity provided an early warning signal in the order of a few seconds before collapse. This was validated by comparison with an analogous signal provided at similar time by an accurate displacement lab measurements system based on optical markers positioned at several points of the tested mock-up.

Centrifuge modelling on seismic failure of MSW landfills with high water level

Landfill failure threatens the safety of surrounding cities and causes soil and water pollution. High water levels can usually spur landfill failure. With the presence of earthquake, landfill instability is triggered in a greater possibility. However, the dynamic response and failure mechanism of landfills with high water level subjected to earthquakes are not yet clearly understood, and relevant experimental studies are quite scarce. This study includes a series of seismic centrifuge tests to investigate the seismic response of the landfill at different water levels. An improved method is proposed to prepare synthetic municipal solid wastes (MSWs) with similar static-dynamic properties to the actual MSWs. The failure and evolution mechanism of landfills with high water levels induced by the earthquake is revealed. Significant transitions are observed in the dynamic response of deformation, acceleration, and pore-water pressure as the water level changes. With the rise of water level, the settlement at the top of the landfill decreases first and then increases, while the horizontal displacement at the toe increases slowly, followed by a sudden drop; the acceleration amplification coefficient in the middle of the landfill increases first and then decreases; the dynamic pore-water pressure gradually decreases from positive to negative, but oscillates at the moderate water level. Three failure criteria and a hydro-earthquake coupled failure limit are proposed to demonstrate the combined effect of water level and earthquake on landfill stability. The test results provide a basis to establish seismic failure standards for landfills with different water levels and guide the seismic instability design of landfills with high water level.

Detection and Characterization of Seismic and Acoustic Signals at Pavlof Volcano, Alaska, Using Deep Learning

AbstractVolcanic tremor is a semi‐continuous seismic and/or acoustic signal that occurs at time scales ranging from seconds to years, with variable amplitudes and spectral features. Tremor sources have often been related to fluid movement and degassing processes, and are recognized as a potential geophysical precursor and co‐eruptive geophysical signal. Eruption forecasting and monitoring efforts need a fast, robust method to automatically detect, characterize, and catalog volcanic tremor. Here we develop VOlcano Infrasound and Seismic Spectrogram Network (VOISS‐Net), a pair of convolutional neural networks (one for seismic, one for acoustic) that can detect tremor in near real‐time and classify it according to its spectral signature. Specifically, we construct an extensive data set of labeled seismic and low‐frequency acoustic (infrasound) spectrograms from the 2021–2022 eruption of Pavlof Volcano, Alaska, and use it to train VOISS‐Net to differentiate between different tremor types, explosions, earthquakes and noise. We use VOISS‐Net to classify continuous data from past Pavlof Volcano eruptions (2007, 2013, 2014, 2016, and 2021–2022). VOISS‐Net achieves an 81.2% and 90.0% accuracy on the seismic and infrasound test sets respectively, and successfully characterizes tremor sequences for each eruption. By comparing the derived seismoacoustic timelines of each eruption with the corresponding eruption chronologies compiled by the Alaska Volcano Observatory, our model identifies changes in tremor regimes that coincide with observed volcanic activity. VOISS‐Net can aid tremor‐related monitoring and research by making consistent tremor catalogs more accessible.

Climate Change inflicted Environmental Degradation leading to the Crumbling of Arctic Ecosystem

The Arctic and Antarctic regions serve as the air conditioners of planet Earth. The polar regions located thousands of miles away from us determine the climatic patterns of our geographical area. They maintain our planet at bearable temperatures which are ideal for the existence of diverse flora and fauna and to support different types of ecosystems all around the world. Apart from controlling the temperatures, they also regulate ocean currents which in turn have an effect on the monsoons, winds, hurricanes etc. The poles were pristine till a few decades back. Due to man’s greed, the poles started deteriorating at an alarming scale. Climate change, biodiversity changes, oil drilling, seismic testing, toxin accumulation are a few of the challenges faced by the Arctic ecosystem having serious effects on its topography, terrestrial and marine life-forms and the whole ecosystem. Due to the alarming scale of global warming, there is also the danger of permafrost meltdown which can unleash a plethora of dangerous pathogens buried underneath and also let out the huge amounts of locked down carbon. The crumbling of the polar ecosystem is leading to rampant consequences not only in the poles but also elsewhere in the world thousands of miles away. Here, we attempt to discuss the repercussions of the crumbling Arctic ecosystem due to the physical, chemical and geological changes caused by such anthropogenic activities and look at the efforts being carried out to save the Arctic ecosystem in a frantic effort to save our planet.

Seismic cyclic test of perforated replaceable link for eccentrically braced frames

This study introduces a design comprising a unweakened link and four variants of perforated replaceable links, denoted as specimens RX1 (unweakened link), RX2 and RX3 (with circular holes of 50 mm diameter on the web), RX4 and RX5 specimens (with elliptical holes on the web), and RX6 and RX7 specimens (with weakened flanges and circular holes of 50 mm and 80 mm diameter on the web). Seven link specimens underwent cyclic loading tests. RX1 ultimately failed due to tearing of the weld at the connection between the flange and the end plate, while RX2 to RX7 exhibited deformation concentrated within the energy dissipating region, ceasing loading upon failure of this region, demonstrating enhanced safety and stability. All specimens exhibited relatively full hysteretic curves, with a decrease in the area of hysteretic curves corresponding to an increase in the web perforation ratio. The overstrength coefficient for specimen RX1 ranged from 1.81 to 1.82, while for specimens RX2 to RX7, it ranged from 1.80 to 3.65. Not only were the overstrength coefficients greater than RX1, but also the cumulative energy dissipation was higher than RX1. This indicates that RX2 to RX7 can accommodate larger plastic deformations, effectively utilizing plastic deformation for energy dissipation, thereby exhibiting superior safety. Moreover, an increase in web perforation ratio and weakening of the flanges resulted in a decrease in the overstrength coefficient, load-bearing capacity, and plastic deformation capacity of the specimens. Ductility decreased with increasing web perforation ratio but increased with flange weakening. Additionally, through analysis of link replacement time and residual rotation of links after unloading, it was observed that perforated replaceable links exhibited favorable replaceability.

Signal characteristics of surface seismic explosive sources near the West Antarctic Ice Sheet divide

Abstract Seismic imaging in 3-D holds great potential for improving our understanding of ice sheet structure and dynamics. Conducting 3-D imaging in remote areas is simplified by using lightweight and logistically straightforward sources. We report results from controlled seismic source tests carried out near the West Antarctic Ice Sheet Divide investigating the characteristics of two types of surface seismic sources, Poulter shots and detonating cord, for use in both 2-D and 3-D seismic surveys on glaciers. Both source types produced strong basal P-wave and S-wave reflections and multiples recorded in three components. The Poulter shots had a higher amplitude for low frequencies (&lt;10 Hz) and comparable amplitude at high frequencies (&gt;50 Hz) relative to the detonating cord. Amplitudes, frequencies, speed of source set-up, and cost all suggested Poulter shots to be the preferred surface source compared to detonating cord for future 2-D and 3-D seismic surveys on glaciers.

Distributed acoustic sensing for seismic surface wave data acquisition in an intertidal environment

The application of distributed acoustic sensing (DAS) for shallow marine seismic investigations is assessed, in particular with respect to the collection of seismic surface wave data in an intertidal setting. Appropriate selection and directional sensitivity of fiber-optic cables is considered and the measured data is validated with respect to conventional seismic data acquisition approaches, using geophones and hydrophones, along with independent borehole and seismic cone penetration test (SCPT) data. In terms of cable selection, a reduction in amplitude and frequency response of an armored cable is observed, when compared with an unarmored cable. For seismic surface wave surveys in an offshore environment where the cable would need to withstand significant stresses, the use of the armored variant with limited loss in frequency response may be acceptable from a practical perspective. The DAS approach also has indicated good consistency with conventional means of surface wave data acquisition, and the inverted [Formula: see text] also is very consistent with downhole SCPT data. Observed differences in phase velocity between high tide (Scholte wave propagation) and low tide (Rayleigh wave propagation) are not thought to be related to the particular type of interface wave due to shallow water depth. These differences are more likely to be related to the development of capillary forces in the partially saturated granular medium at low tide. Overall, this study demonstrates that our novel approach of DAS using seabed fiber-optic cables in the intertidal environment is capable of rapidly providing near-surface S-wave velocity data across considerable spatial scales (multikilometer) at high resolution, which is beneficial for the design of subsea cables routes and landfall locations. The associated reduction in deployment and survey duration, when compared with conventional approaches, is particularly important when working in the marine environment due to potentially short weather windows and expensive downtime.

The joint controls of tectonism, sedimentation and diagenesis on reservoir quality in the East China Sea Basin

Variation in reservoir quality is especially important in low-permeability and tight sandstone reservoirs. By using log, seismic and core test data, we developed a method that uses tectonism, sedimentation and diagenesis to evaluate sweet spot distribution of the third (Mbr 3), fourth (Mbr 4) and fifth (Mbr 5) members of the Oligocene Huagang Formation in the Xihu Depression, East China Sea Basin. Sweet spot maps of the Mbr 3, Mbr 4 and Mbr 5 sandstone reservoirs were compiled by superposing tectonic locations, depositional microfacies and diagenetic facies. Sweet spots were classified into three types. Mbr 3 exhibits type I and type II sweet spots, Mbr 4 exhibits type I, type II and type III sweet spots, and Mbr 5 exhibits type II and type III sweet spots. In the Oligocene, tectonism and climatic controlled the depositional microfacies, sandstone grain size and clastic composition of the Mbr 5, Mbr 4 and Mbr 3 members, which were deposited in a braided river delta setting that ranged from delta-front distal part to proximal part. From late Oligocene to present, along with depositional microfacies, diagenetic stage, diagenetic facies and reservoir properties, the joint control of tectonism, sedimentation and diagenesis determined the distribution of diagenetic facies, and was used to develop a synthetic pattern for reservoir quality variation.

Seismic source of rock drill and its application in in-situ vibration monitoring of rock mass

This study suggests the use of a seismic source of a rock drill as a new excitation method for real-time monitoring of the vibration frequency of rock masses in tunnel engineering. In this study, a laboratory rock drill seismic source test system was developed. The rock mass excitation and vibration response under real in situ stress were simulated, and a natural frequency test of different lithologic materials under various in situ stresses was carried out based on the developed system. Empirical equations for estimating natural frequency were established using regression analysis. The test results show that (1) the laboratory rock drill seismic source test system exhibits good performance and can simulate the horizontal excitation process of the tunnel rock drill. Rock drill excitation may be used as the seismic source to continuously measure the in-situ vibration information of the rock mass. (2) The natural frequency of rock is positively correlated with rock elastic modulus and geostress and negatively correlated with rock density. This is not directly related to the seismic source.

Seismic Performance Tests of Prefabricated Concrete Frames with Embedded Composite Lightweight Aggregate Partition Wall Panels

Seismic Performance Tests of Prefabricated Concrete Frames with Embedded Composite Lightweight Aggregate Partition Wall Panels

A hybrid model based on unsupervised learning for seismic response feature extraction and gas-bearing reservoir prediction using longitudinal and transverse waves seismic data in low-degree exploration areas: A case study

Predicting gas-bearing reservoirs from seismic data is a major field of research. Recently, deep learning has been applied to achieve better results; however, challenges such as high sample demand remain. Drilling data are often insufficient, and gas-bearing sample data are difficult to acquire in large quantities, particularly for low-level (new) exploration areas, which limits gas-bearing reservoir prediction by supervised learning. Therefore, this study proposes a hybrid model using unsupervised learning to extract seismic response features and predict gas-bearing reservoir distribution. First, seismic attribute analysis was used to extract as many longitudinal and transverse waves seismic attributes as possible to provide richer information about gas-bearing reservoirs. However, abundant seismic attributes contain a large amount of redundant information, thereby increasing computation time. Thus, principal component analysis (PCA) was used to reduce the dimensions of the extracted multi-component seismic attributes, remove redundant information, and obtain the most important characteristics that are sensitive to gas-bearing reservoirs. The sensitive seismic attributes obtained after the PCA were fed into a self-organizing neural network (SOM) for unsupervised learning. Neurons in the SOM compete with each other to optimize their own features and extract reservoir-sensitive seismic response features for prediction. To evaluate the proposed method, it was applied to part of the Marmousi2 model and real seismic data for validation. The following results were obtained: (1)The results of the synthetic data test results not only proved the effectiveness of the proposed method, but also showed that the method has strong noise resistance capability and is suitable for predicting gas-bearing reservoirs with low signal-to-noise ratio seismic data; (2) Based on the drilling data and sedimentary facies characteristics in the test area, the actual 3D seismic data test results showed that there are four wells that match the predicted results, and the distribution boundaries of the gas-bearing reservoirs they depict are relatively clear; (3) In low exploration areas (areas with few or no wells), this method is important as a guide to hydrocarbon exploration.

Nonlinear model for assessing seismic resilience in nuclear fuel assemblies

Seismic events may lead to vibrations of fuel assemblies in the nuclear reactor cores, thus the dynamic analysis of such vibration of fuel assemblies is essential for the safety design of nuclear reactor plant. In this paper, by considering the friction between fuel pins, we proposed a nonlinear mechanical model for both static and dynamic analysis of fuel assemblies for pressurized water reactor (PWR). The proposed model used a two-beam structure with frictional units to mimic friction and possible contacts in the pin bundle during the static and dynamic loading in the air. By using this approach, we could characterize not only the hysteresis loop during the static bending test (the static slingshot experiment), but also the decrease of resonance frequency with increase of seismic load. Further, maximum contact forces during the seismic test are compared with experiment at various impact locations, and the predictions closely match the experimental findings, affirming the scientific validity and accuracy of the proposed model. The proposed model can be further used to analyzing seismic behavior of the entire reactor core structure, providing valuable insights for assessing reactor structural safety and predictive hazard assessments.

3D Full-Waveform Tomography of Standard Penetration Test-Seismic Wavefields in Karst Florida Limestone

The shallow subsurface across large parts of Florida consists of weathered karst limestone, a spatially variable porous stratigraphy with significant influence in the design and load capacity of deep foundations. For reliable load transfer of the super structure into the bearing soil/rock, detection of voids and weak zones is crucial. This study investigated the capabilities of a recently developed standard penetration test (SPT)-seismic testing method for characterizing a large volume of soil/rock properties with a single SPT. The method utilizes a three-dimensional full-waveform inversion (3D FWI) of wavefields induced by SPT blows at depths (in-depth source) to characterize the subsurface around the SPT borehole. A site in Florida that presents shallow, surface karst limestone, was the location of a field experiment that consisted of two 36- × 18-m areas, each with an SPT at the area center. Seismic wavefields induced by SPT blows at depth were recorded by 72 vertical geophones on the ground surface and analyzed by the 3D FWI. The results revealed that subsurface soil/rock properties were characterized in submeter pixels over a large 3D domain of 24 × 36 × 18 m (depth × length × width). Multiple voids at various depths from 5 to 17 m were successfully detected at the site and confirmed by SPT data. The results suggested that the SPT-seismic method is an efficient tool for site investigation, as a bridge pier or pile group could be designed with only one SPT.