Dip Structure Research Articles

Enhancing seismic feature orientations: A novel approach using directional derivatives and Hilbert transform of gradient structure tensor

Seismic dip calculation serves as a widely employed technique in the realms of seismic interpretation and reservoir characterization, strategically employed to highlight faults and attributes within the seismic volume. Among the various methodologies utilized for estimating structural dip and azimuth, the Gradient Structure Tensor (GST) stands out. This approach involves leveraging the dominant eigenvector of the positive definite GST matrix to ascertain the inline and crossline dip of seismic data.In the initial phase of our innovative proposal, we employed the spectral balancing technique to enhance the fidelity of seismic data. Subsequently, leveraging this groundwork, we introduced an Analytical Directional Gradient Structure Tensor technique, a distinctive adaptation of GST. This novel approach involves the calculation of directive derivatives in both perpendicular and parallel directions to seismic features. By incorporating directive derivatives, our method excels in capturing subtle stratigraphic nuances, particularly in the dipping direction of interest. To validate the accuracy and effectiveness of our approach, we present compelling evidence through the examination of synthetic and real-field seismic volume outcomes. This underscores the robustness and reliability of our proposed method in enhancing the precision of seismic dip calculations and providing valuable insights into subsurface geological features.

Analysis of failure properties of red sandstone with structural plane subjected to true triaxial stress paths

In order to study the mechanical behavior and failure characteristics of rock mass with the structural plane in complex deep stress environment, the QKX-YB200 true triaxial rockburst test system, acoustic emission, and digital video recorder were adopted to conduct true triaxial loading and unloading indoor tests on the red sandstone cube specimens. The results show that: (1) Under true triaxial loading conditions, all specimens propagate in the form of anti-wing crack, and the dip angle of the structural plane is linearly related to the average value of the anti-wing crack propagation angle; under true triaxial unloading conditions, the specimens with structural plane dip angles of 30°, 45°, and 60° propagate in the form of wing crack, while those with a 90° angle propagate anti-wing cracks, and the closure of structural plane is related to the the crack type at the tips of structural plane. (2) The unstable failure stages in the stress–strain curve under true triaxial unloading are longer and exhibit more pronounced fluctuations; the peak strength of the specimens under the conditions of true triaxial loading and unloading decrease first and then increase with the increase of the dip angle, reaching the lowest at 45°. (3) During the true triaxial unloading tests, the rockburst degree of the intact rock specimens is more violent than that of the specimens with a structural plane. Additionally, the dip angle of the structural plane influences the severity of rockbursts under the same stress path. (4) The crack propagation mechanism and the closure degree of structural planes under different true triaxial stress paths and dip angles are discussed. It is observed that the crack initiation mode around the structural plane tips and the crack mode near free surface are closely related to the stress environment in different areas of the specimens. (5) Based on the indoor test results and previous experimental data, the differences in peak strength characteristics between open structural planes and closed structural planes are preliminarily analyzed and compared.

Shaking Table Test on the Seismic Behavior of Fractured Rock Slopes with Dipping and Anti-dipping Layered Structures

Abstract Rock slopes with layered fractured structure are widely distributed in the mountainous areas of Southwest China. Under earthquake, these slopes are highly susceptible to disasters such as collapse, landslides, etc., adversely impacting the operation safety of transportation systems. This study aims to investigate the difference in seismic behaviors of two types of fractured rock slopes with typical dipping and anti-dipping layered structures. To do so, two sets of large-scale shaking table tests on the two typical fractured rock slopes were performed. The emphasis was made on the different failure mechanism of these slopes tested when subjected to four different seismic loadings with step-wise increase in amplitudes up to 0.7 g. We observed a three-stage destabilization process in both cases. For the dipping slope, the initial formation of microcracks and then their rapid development was followed by generation of terraced sliding surface through slope, whereas the formation of microcracks was followed by toppling of rock front until final collapse for the anti-dipping slope. Both slopes exhibit elevation amplification effects upon seismic loads as previously observed in other studies of similar slopes. The acceleration amplification effects near the bedrock interface and within slopes are more significant in the dipping case compared to the anti-dipping one. These effects are much enhanced at the top of slopes considered when the peak input acceleration exceeds 0.4 g. Further, Hilbert marginal spectrum analysis indicates that a sliding failure surface above the midslope was formed for the dipping slope, whereas the anti-dipping slope experienced more severe damages at the slope shoulder. The outcomes of this study are of important potential to assist the risk assessment and early warning of seismic hazards of fractured rock slopes.

Higgs interference effects in top-quark pair production in the 1HSM

We present a next-to-leading-order (NLO) study of the process pp (→ {h1, h2}) →tt¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ t\\overline{t} $$\\end{document} + X in the 1-Higgs-singlet extension of the Standard Model with an additional heavy Higgs boson h2 that mixes with the light Higgs boson h1. This process is subject to large interference effects between loop-induced Higgs-mediated amplitudes and the QCD continuum background which tend to overcompensate any resonance contributions. A reliable modelling of the resulting top-pair invariant mass shapes requires the inclusion of higher-order QCD corrections, which are presented here. The computation of these NLO corrections is exact in all contributions but in the class of non-factorisable two-loop diagrams which are included in an approximate way such that all infrared singular limits are preserved. We present numerical results for several benchmark points with heavy Higgs masses in the range 700–3000 GeV considering the production of stable top quarks. We find that the interference effects dominate the BSM signal yielding sharp dip structures instead of resonance peaks. The significance and excludability of the BSM effect is explored for the LHC Run 2, Run 3 and HL-LHC.

Properties of observable mixed inertial and gravito-inertial modes in gamma Doradus stars

The space missions Kepler and TESS provided a large number of highly detailed time series for main-sequence stars, including gamma Doradus stars. Additionally, numerous gamma Doradus stars are to be observed in the near future thanks to the upcoming PLATO mission. In gamma Doradus stars, gravito-inertial modes in the radiative zone and inertial modes in the convective core can interact resonantly, which translates into the appearance of dip structures in the period spacing of modes. Those dips are information-rich, as they are related to the star core characteristics. Our aim is to characterise these dips according to stellar properties and thus to develop new seismic diagnostic tools to constrain the internal structure of gamma Doradus stars, especially their cores. We used the two-dimensional oscillation code TOP to compute sectoral prograde and axisymmetric dipolar modes in gamma Doradus stars at different rotation rates and evolutionary stages. We then characterised the dips we obtained by their width and location on the period spacing diagram. We found that the width and the location of the dips depend quasi-linearly on the ratio of the rotation rate and the Brunt-Väisälä frequency at the core interface. This allowed us to determine empirical relations between the width and location of dips as well as the resonant inertial mode frequency in the core and the Brunt-Väisälä frequency at the interface between the convective core and the radiative zone. We propose an approximate theoretical model to support and discuss these empirical relations. The empirical relations we established could be applied to dips observed in data, which would allow for the estimation of frequencies of resonant inertial modes in the core and of the Brunt-Väisälä jump at the interface between the core and the radiative zone. As those two parameters are both related to the evolutionary stage of the star, their determination could lead to more accurate estimations of stellar ages.

Evidence for a Cyclotron Absorption Line and Spectral Transition in EXO 2030+375 during the 2021 Giant Outburst

Based on Insight-HXMT observations of EXO 2030+375 during its 2021 giant outburst, we report the analysis of pulse variations and the broadband X-ray spectrum, and find the presence of a potential cyclotron resonant scattering feature (CRSF) with the fundamental line at ∼47 keV from both average spectra and phase-resolved spectroscopy. During the outburst, the source reached an X-ray luminosity of ∼1038 erg s−1 from 2 to 105 keV at a distance of 7.1 kpc. The X-ray pulsar at the spin period of 41.27 ± 0.61 s exhibits complex timing and spectral variations with both energy and luminosity during the outburst. The shapes of the pulse profiles show the single main peak above ∼20 keV, while appearing to exhibit multipeak patterns in low-energy bands, and the transition of the 10–20 keV pulse profiles from multipeak to single peak is observed at ∼0.8 × 1038 erg s−1, which suggests the evolution from the subcritical luminosity (pencil-beam dominated) to the supercritical luminosity (fan-beam dominated) regime. A dip structure before the energy of the CRSFs is found in the pulse fraction–energy relation of EXO 2030+375 near the peak luminosity. A detailed analysis of spectral parameters showed that the power-law photon index exhibits three distinct trends as luminosity increases, and these spectral changes also signify a spectral transition from subcritical to supercritical regimes. The critical luminosity infers a magnetic field of ∼(4.8−6.0) × 1012 G, which supports the presence of the cyclotron line at ∼47 keV. A Comptonization model applied for the broad X-ray spectra during the outburst also suggests the surface magnetic field ranging from ∼(5−9) × 1012 G.

Integrated Technique Provides Effective Water Diagnostics in Tight Sand

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 3864145, “Evaluating the Hydraulic Fracture Through Acoustic Reflection Imaging and Production Logging for Water Diagnostic Beyond the Wellbore: A Case Study From Chang 8 Tight Sand in the Ordos Basin, China,” by Guangsheng Liu, Dajian Li, and Gang Zheng, PetroChina, et al. The paper has not been peer reviewed. _ The Triassic Chang 8 tight sand reservoir in the Xifeng block of the Ordos Basin features low permeability, which means that hydraulic fracturing and subsequent waterflooding were performed during its development phase. Water breakthrough was encountered after a short period of oil production. A solution of borehole acoustic reflection imaging combined with production logging was proposed in a horizontal well suffering from high water cut. The objective was to determine which stages contributed most to water production, understand the cause, and, ultimately, create a water shutoff plan. Introduction The Ordos Basin, with an area of approximately 2.5×105 km2, is in North China. The Upper Triassic Yanchang formation is subdivided into the Chang 1 to 10 members, from top to bottom. It contains significant oil reserves in siltstone and sandstone reservoirs, especially in Chang 6 through Chang 8, that have been the major oil-producing resources in recent years. In the Triassic Chang 8 tight sand reservoir, horizontal well drilling and multiple-stage hydraulic fracturing have become common practice. In the study block, the well of interest was hydraulically fractured by coiled tubing with sand-jet perforation and fracturing operations in one run with a retrievable packer in the bottomhole assembly of the coiled tubing. In the study block, when some producing wells encountered water breakthrough, traditional water diagnostics using production logging was not enough; a survey to detect hydraulic fractures beyond the wellbore was needed. Theory and Methods Borehole Acoustic Reflection Imaging. The processing workflow for acoustic reflected waves mainly consists of two parts. The first is a filtering process to suppress the borehole mode and noise in order to preserve the reflected wave. The second is to migrate the reflected wave to the true position of a reflector. The conventional migration method used for acoustic reflection imaging normally requests previous information relating to reflector dip and produces 2D images, which show the reflector shape but have hard-to-extract precise quantitative information. A trial reflector-migration method covered in the literature was introduced in 2016 that does not require input of structure dip and is of high resolution. A 3D slowness-time-coherence method was developed in 2018, also covered in the literature, that could determine the true dip, azimuth, and distance of a reflector.

Widening the Gamut of Structural Colors of Gold via Insulator–Metal Bilayer Coatings

Tuning the color of Au has been a longstanding problem in the luxury industry. Conventional approaches, involving Au alloying, compromise purity and demand distinct alloy compositions for each hue. This study demonstrates a lithography‐free method for generating structural colors on a gold surface by adjusting the thickness of titanium dioxide, a high‐index dielectric. While color tuneability is limited if TiO2 is coated directly on the Au surface, a range of vivid colors can be generated if a 50−100 nm thick AuAl2 underlayer is used. AuAl2, an accepted alloy for purple gold, broadens the color gamut, providing a protective coating without diminishing gold purity. The reflectance dip of the bilayer structure exhibits a significant red shift with increasing thickness of the TiO2 layer, allowing diverse colors by TiO2 insulator tuning. Simulation studies corroborate experimental results, affirming that coating a TiO2 layer on the AuAl2 underlayer yields a wide range of colors. This method, based on thin‐film interference, shows promise for widespread use, offering a broad spectrum of structural colors in an industry striving for diverse Au color representation.

Higher order contribution to ion-acoustic Korteweg–de Vries (KdV) soliton in unmagnetized quantum plasmas with arbitrary degeneracy of electrons

The propagation of nonlinear ion-acoustic Korteweg–de Vries (KdV) solitons and dressed solitons (with higher order contribution term) in unmagnetized quantum plasmas with arbitrary degeneracy of electrons is investigated using quantum hydrodynamic model. The reductive perturbation method is used to derive the first order nonlinear ion-acoustic KdV equation and also higher order contribution of inhomogeneous differential equation is obtained for the dressed ion-acoustic wave soliton in arbitrary degenerate electron plasmas. Moreover, the higher order inhomogeneous differential equation is solved (nonsecular solution is obtained) using the renormalization method. The conditions for the validity of the higher order correction are also discussed in detail for ion-acoustic solitons in unmagnetized arbitrary degenerate electrons plasma case. The effects of chosen values of electron temperature, equilibrium fugacity and corresponding electron density of a physical quantum plasma system and quantum diffraction parameter H (for two conditions i.e., H < 2 or H > 2) on the amplitude and width of the KdV and dressed ion-acoustic wave solitons for both electrostatic potential hump (compressive) or dip (rarefactive) structures are investigated. The numerical plots are also presented for illustration with numerical values of a physical partially degenerate electrons plasma system exist in the astrophysical or laboratory conditions.

Enhancing productivity through work study - A case of electric power pole cross arm fabrication

In the area of globalization any manufacturing industry must be competent in terms of productivity, quality, cost and delivery. A fundamental improvement in production is necessary to succeed in the international markets. Work study is one of the earliest scientific management methods used to determine the best way to perform production tasks in order to reduce idle time and worker fatigue as a result, increase productivity. Kombolcha Steel Products Industry, the member of MIDROC Ethiopia Technology Group, producing a variety of metal and engineering products, such as steel poles, steel structures, structural hot dip galvanization, corrugated sheet metal, etc. The company's main focus was meeting the delivery deadlines, with little attention to implementing standard working method and procedures during the production. The inefficient method of piercing the holes in the u-channels to fabricate the electric pole cross arms is causing a drop in productivity.The primary objective of the current study is to identify the bottlneck in the process of electric power poles cross arms fabrication, to set standard time for the process and reduce the cycle time. Time and method studies were used to identify the flaws in the current fabrication process and layout design. The efficient technique to manufacture the product has been replaced by redesigning and implementing a new layout. This arrangement accelerated the process by reducing the idle time for the three punching machines that undertake the piercing operations. The modified layout raised production from the target daily production of 420 pieces to 720 pieces in 8 h, resulting in a 71 % reduction in the previous work cycle from 65 to 39 s. After a time and method study, a simple change in the layout with no capital investment not only increased the company's productivity and profitability, but it also reduced worker fatigue due to extra material handling operations of raw materials and intermediate products.

Waveform inversion with structural regularizing constraint based on gradient decomposition

Abstract Full waveform inversion (FWI) can simultaneously update low-to-medium wavenumber velocity components and high-wavenumber velocity components. However, if seismic data lack large-offset data and effective low-frequency components, FWI updates will be dominated by high-wavenumber velocity perturbation. Meanwhile, providing that the initial model is inaccurate, inversion will have the problem of local minima. In this study, FWI is developed with structural regularizing constraint based on gradient decomposition (RGDFWI). By correlating the separated forward wavefield and backward wavefield with specific propagating direction, FWI gradient is decomposed into tomography-mode gradient and migration-mode gradient. We propose an optimized strategy taking full advantage of the two modes of FWI gradient. On the one hand, we use tomography-mode gradient to enhance low-to-medium wavenumber updates. On the other hand, we use migration-mode gradient to apply structural regularizing constraint by estimating structure dip and adding sparsity constraint in Seislet domain. During the inversion process, high-wavenumber structural information constrains and guides low-wavenumber model updates. The results of two numerical tests, Marmousi model test and Overthrust model test, validate the optimized strategy, which can produce a better initial velocity model for FWI. The inversion finally generates a high-precision and high-resolution velocity model.

Speed of sound and polytropic index in the Polyakov-loop Nambu-Jona-Lasinio model

We investigate the speed of sound and polytropic index of quantum chromodynamics (QCD) matter in the full phase diagram based on a three-flavor Polyakov-looped Nambu-Jona-Lasinio (PNJL) model. The speed of sound and polytropic index in isothermal and adiabatic cases all have a dip structure at the low chemical potential side of the chiral phase transition boundary, and these quantities reach their global minimum values at the critical end point (CEP) but are not completely zero, where the values in adiabatic are lightly greater than those in isothermal. Different from the speed of sound, the polytropic index rapidly form a peak after crossing the chiral phase transition boundary, which is observed for the first time. Along the hypothetical chemical freeze-out lines, the speed of sound rapidly decreases near the CEP, followed by a small spinodal behavior, while the polytropic index, especially in isothermal, exhibits a more pronounced and nearly close to zero dip structure as it approaches the CEP. Published by the American Physical Society 2024

Brittle rock mass failure in deep tunnels: The role of infilled structural plane with varying dip angles

Filled rock discontinuities are commonly encountered in underground engineering excavations, and their mechanical behavior has a significant impact on the stability of surrounding rocks. However, their performance under three-dimensional stress conditions has rarely been explored in the past. In this study, we summarized the typical failure characteristics of filled structural planes in deep-buried tunnels and conducted laboratory true triaxial tests on granite specimens to investigate the effect of dip angle and infill thickness on the failure characteristics of high-stress brittle surrounding rocks. The study monitored the characteristics of vertical stress-displacement, acoustic emission, acceleration, and failure process of granite specimens during the loading process and revealed the failure mechanism of brittle rock masses under the influence of infill thickness and structural plane dip angle. The results showed that the dip angle of structural planes has a significant influence on the failure mode of rock masses in deep tunnels. There exists a critical range of dip angles, within which the rock mass undergoes shear slip failure along the pre-existing structural plane, manifested by rock spalling near the structural plane. Beyond this critical range, the rock mass experiences strain-type brittle failure, characterized by violent rock ejection. Furthermore, the filling of structural planes can change the failure mode of rock masses and lead to more severe damage when the friction coefficient of the structural plane falls below a specific threshold. Additionally, it was revealed that a perpendicular ejection force exists on the free surface of the rock mass under loading, which is approximately vertical to the normal direction and is the primary factor responsible for the formation of vertical parallel cracks within the rock mass. The findings of this work are of paramount importance for comprehending the failure characteristics of deep-buried tunnels containing infilling joints.

Thermal noise energy regulation in a double-cavity magnomechanical system

We investigate the thermal transport characteristics in a double-cavity magnomechanical system with a yttrium iron garnet sphere. We explore mainly the performance parameter of the thermo-phonon flux flowing from the thermal bath of a mechanical motion into the magnomechanical system and study its dependence on the cavity field detuning and decay, the magnon-photon and magnon-phonon coupling strengths, and the Kerr nonlinear coefficient of magnon. We find that the direction and magnitude of the steady-state thermophonon flux in the magnomechanical system can be controlled flexibly by modulating these system parameters. In particular, the interference effect of quantum transitions in the multi-mode magnomechanical system results a multiple dip structure in the heat flow pattern. The results obtained her e help demonstrate the thermal noise energy harvesting and rectification by the cavity magnomechanical setup.

Modeling the influence of climate on groundwater flow and heat regime in Brandenburg (Germany)

This study investigates the decades-long evolution of groundwater dynamics and thermal field in the North German Basin beneath Brandenburg (NE Germany) by coupling a distributed hydrologic model with a 3D groundwater model. We found that hydraulic gradients, acting as the main driver of the groundwater flow in the studied basin, are not exclusively influenced by present-day topographic gradients. Instead, structural dip and stratification of rock units and the presence of permeability contrasts and anisotropy are important co-players affecting the flow in deep seated saline aquifers at depths &amp;gt;500 m. In contrast, recharge variability and anthropogenic activities contribute to groundwater dynamics in the shallow (&amp;lt;500 m) freshwater Quaternary aquifers. Recharge fluxes, as derived from the hydrologic model and assigned to the parametrized regional groundwater model, reproduce magnitudes of recorded seasonal groundwater level changes. Nonetheless, observed instances of inter-annual fluctuations and a gradual decline of groundwater levels highlight the need to consider damping of the recharge signal and additional sinks, like pumping, in the model, in order to reconcile long-term groundwater level trends. Seasonal changes in near-surface groundwater temperature and the continuous warming due to conductive heat exchange with the atmosphere are locally enhanced by forced advection, especially in areas of high hydraulic gradients. The main factors controlling the depth of temperature disturbance include the magnitude of surface temperature variations, the subsurface permeability field, and the rate of recharge. Our results demonstrate the maximum depth extent and the response times of the groundwater system subjected to non-linear interactions between local geological variability and climate conditions.

Geologic causatives of the stratigraphic and structural heterogeneties of Baharyia formation, based on their seismic interpretation, Razzak field, Western Desert, Egypt

Evaluation of seismic attributes and seismic reflection characteristics analysis of Razzak Field was undertaken by subdividing the study area rock units. There are four seismo-facies units of varying parameters from top to bottom. These units are comparable to the Apollonia and Khoman Formations; the Abu-Roash Formation; Baharyia Formation and Alamein Formation. The seismo-facies unit 1 of the Apollonia and Khoman Formations reveal parallel to sub-parallel layering, with thickness increases northwards. The lithological distribution consists of limestone with minor clay intercalations with facies varying from middle neritic graded to outer neritic. Unit 2 of the Abu-Roash Formation shows divergent layering, with a thickness increasing gradually northwards and eastwards. The lithological distribution shows predominance of carbonate, sandstone occurring in minor portions and laterally graded into shale with littoral facies ranging to inner and middle neritic facies. Unit 3 of the Baharyia Formation reveals chaotic and oblique layering with a time thickness increases towards northeast and southwest parts, the lithological distribution exhibited sand and shale with minor limestone streaks, with facies varied changed from continental to inner-middle neritic, unit 4 of the Alamein Formation shows variation from parallel-subparallel orientation to oblique and chaotic with thickness increasing towards northwards and eastwards, the lithological distribution exhibited dolomitic limestone with minor streaks of limestone with facies varied from middle neritic facies to outer neritic and bathyal. Finally, the results are integrated to build up a seismo-stratigraphic model of the evaluated area of the northwestern Desert of Egypt. Seismic interpretation involves the construction of structure contour maps, in terms of time and depth, on the tops of the Apollonia, Abu-Roash, Baharyia and Alamein Formations. These maps show three structural closures, due to folding, that are dissected by NW–SE faults, analysis of relevant structural and stratigraphic seismic attributes such as root-mean-square amplitude, local structural dip, variance, ISO frequency component, sweetness and acoustic impedance average energy applied on reservoir tops, to enhance the visibility of faults, geological interpretation and the physical parameters of the subsurface related to lithology and stratigraphy for reservoir characterization. Finally, the results obtained are used to construct a seismic structural model. Integration of seismic and stratigraphic data is used to build a geological model of the northwestern Desert of Egypt.

Quantitative seismic fracture characterization of a sandstone reservoir — Decatur, Illinois Basin

The Illinois Basin Decatur Project, a carbon capture and sequestration task, was undertaken to sequester 1 million tonnes of CO2 into a sandstone reservoir. A 3D seismic survey was conducted to characterize the reservoir. A geomodel was developed from seismic data, inversion results, and well data to geostatistically map the storage potential of the reservoir. However, no fracture model was created or utilized in this exercise. Fractures inherently influence the porosity and permeability of a reservoir. Ignoring them in reservoir characterization is not an optimal reservoir management practice. The image-log interpretation from a few vertical wells drilled in the area shows the bedding plane dips, but no fracture has been identified. However, the lack of fracture crossings in a few vertical wells does not imply that a formation is devoid of fractures altogether. Hence, seismic fracture characterization (leveraging the dense 3D seismic data) is necessary for a reservoir characterization exercise. We utilized the publicly available Decatur 3D seismic data set to run a seismic fracture characterization workflow to delineate potential fracture corridors present in the reservoir. We calculated three edge detection attributes (structural tensor, structure-oriented semblance, and structural dip) in combination to delineate the fracture lineaments. Our workflow extracts several quantitative measures of the seismic lineaments such as dip, azimuth, area, and length, which can be analyzed statistically. The principal focus of this work is to find a way forward to integrate the fractures from seismic data in a geologic model that can be utilized in simulations. Based on our interpretation of seismic fractures, we created a discrete fracture network that can be a building block for creating a finer-resolution fracture model. We also explored the fractal characteristics of seismic-derived fracture lineaments as a way forward for generating discrete fracture networks.

Polarization control of above-threshold ionization spectrum in elliptically polarized two-color laser fields

We study the above-threshold ionization (ATI) process of atoms exposed to fundamental and high-frequency lasers with arbitrary ellipticity by applying the frequency-domain theory. It is found that the angular-resolved ATI spectrum is sensitive to ellipticities of two lasers and emitted angles of the photoelectron. Particularly for the photon energy of the high-frequency laser more than atomic ionization potential, the width of plateau tends to a constant with increasing ellipticity of fundamental field, the dip structure disappears with increasing ellipticity of the high-frequency field. With the help of the quantum channel analysis, it is shown that the angular distribution depends mainly on the ellipticity of high-frequency field in the case that its frequency is high. Moreover, one can see that the maximal and minimal energies in quantum numerical results are in good agreement with the classical prediction. Our investigation may provide theoretical support for experimental research on polarization control of ionization in elliptically polarized two-color laser fields.

Approach to Perforation Interval Selection Uses AI-Assisted Image Interpretation

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 216856, “ML-Driven Integrated Approach for Perforation Interval Selection Based on Advanced Borehole-Image AI-Assisted Interpretation,” by Alexander Petrov, SPE, Mounir Belouahchia, SPE, and Abdelwahab Noufal, SPE, ADNOC. The paper has not been peer reviewed. _ In the complete paper, the authors propose an artificial-intelligence (AI)-assisted work flow that uses machine-learning (ML) techniques to identify sweet spots in carbonate reservoirs. This process involves annotation of geologic features using a well database, with supervision from subject-matter experts (SMEs). The resulting ML model is tested on new wells and can identify pay zones, perforation intervals, and stress analysis. The models successfully detect fractures, breakouts, bedding planes, vugs, and slippage passages with pixel-level precision, reducing borehole-image (BHI) analysis time. BHI Interpretation and Preprocessing The use of BHIs requires manual interpretation and data identification, heavily relying on the expertise and time of SMEs. A widely adopted approach to address this challenge is the use of supervised computer-vision algorithms, a subfield of AI. These algorithms optimize the task function or model based on examples they have learned from data during training. However, when applied to BHIs, certain ML challenges must be addressed, including the following: - Detecting features in wells from different reservoirs using a model trained on wells from one reservoir can be highly challenging because reservoirs may exhibit distinct geological characteristics. - The handling of parts of BHIs with missing data, depicted by vertically slanted white strips, poses considerable difficulty. Therefore, the authors created a deep-learning approach based on a generative adversarial network architecture to fill the gaps automatically (Fig. 1). - The labels provided by geologists often do not have pixelwise precision, causing the machine to become confused while trying to learn inconsistent patterns. The authors use a convolutional neural network (CNN) to compute a probability map for pixels belonging to specific classes. In this application, a class is defined as any of the heterogeneities in the BHI; however, this method is applicable to any type of heterogeneities in an image. After training, the CNN module provides the optimal probability for each pixel in the image. To classify regions in the BHI based on heterogeneities, a class-specific threshold is established. Pixels with values above the thresholds are assigned to the corresponding class, while those below the thresholds are assigned to the background. BHI-Derived Porosity A new approach for borehole-derived porosity was developed in-house to overcome the limitations of existing techniques widely used in the industry. This approach capitalizes on BHIs for multiple analyses, including structural dip assessment, fault and fracture identification, and determination of minimum and maximum horizontal stress orientation. However, its primary strength lies in quantifying the fraction of secondary porosity in heterogeneous or dual-porosity carbonate formations. The authors have devised a novel method that uses borehole electrical images to conduct porosity and image connectivity analysis. By implementing this technique, essential information can be extracted regarding the spatial distribution of porosity and the extent of secondary porosity fraction.

The role of the Red Sea rift and the inherited geological structures in the seismo-volcanic activity along the rift flanks

The role of the Red Sea rift on the development and the discrepancy of the seismo-volcanic activity along its flanks is still a debate. Here we tried to resolve this debate by a high-resolution tomographic imaging of the northern Red Sea subsurface structures. For the first time, a large number of arrival time data from the Saudi and Egyptian seismic networks were used. The area comprises the Lunayyir volcanic field in the Saudi Arabia, the Abu-Dabbab seismogenic zone in the Egyptian Red Sea coast, and the Zabargad Shear Zone in the Red Sea. This study revealed clear images of the Red Sea rift-related structures along its flanks. The subsurface extension of the different shear and suture zones existing in the Arabian Nubian shield are well imaged. It is found that the Lunayyir seismo-volcanic activity is possibly controlled by the reactivation of the Yanbu suture zone that is associated with steeply northwestward dipping structure. The suture detachments were observed and identified across the Red Sea as low-V channels. The Egyptian Eastern Desert is found to be highly deformed with crustal-scaled low-V structures which were inherited from the early period of Gondwana collision. The NE-SW strike slip faults along the Red Sea were found to be a part of this deformation that are extended deeply in the crust. The Abu-Dabbab and Marsa-Alam areas were strongly influenced by this deformation with possible magma intrusions. This study provides new insights on the role of the Red Sea in the seismo-volcanic activity along its flanks.