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On efficient frequency-domain full-waveform inversion with extended search space Geophysics (IF 2.609) Pub Date : 2021-02-24 Hossein S. Aghamiry; Ali Gholami; Stéphane Operto
Efficient frequency-domain full-waveform inversion (FD-FWI) of wide-aperture data is designed by limiting inversion to a few frequencies and by solving the Helmholtz equation with a direct solver to process multiple sources efficiently. Some variants of FD-FWI, which process the wave equation as a weak constraint, have been proposed to increase the computational efficiency or extend the search space
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Noise types and their attenuation in towed marine seismic: A tutorial Geophysics (IF 2.609) Pub Date : 2021-02-23 Volodya Hlebnikov; Thomas Elboth; Vetle Vinje; Leiv-J. Gelius
The presence of noise in towed marine seismic data is a long-standing problem. The various types of noise present in marine seismic records are never truly random. Instead, seismic noise is more complex and often challenging to attenuate in seismic data processing. Therefore, we have examined a wide range of real data examples contaminated by different types of noise including swell noise, seismic
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Adaptive frequency-domain nonlocal means for seismic random noise attenuation Geophysics (IF 2.609) Pub Date : 2021-02-22 Hang Wang; Yangkang Chen
Nonlocal means (NLM) is one of the classic patch-based methods for random noise attenuation. It assumes that a significant amount of redundant information exists in similar patches, which can be used to restore the original data. However, this method is computationally expensive due to a large number of overlapping patches. In addition, because this method uses a weighted average of patches to suppress
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A finite-difference iterative solver of the Helmholtz equation for frequency-domain seismic wave modeling and full-waveform inversion Geophysics (IF 2.609) Pub Date : 2021-02-23 Xingguo Huang; Stewart Greenhalgh
We have developed a finite-difference iterative solver of the Helmholtz equation for seismic modeling and inversion in the frequency domain. The iterative solver involves the shifted Laplacian operator and two-level preconditioners. It is based on the application of the preconditioners to the Krylov subspace stabilized biconjugate gradient method. A critical factor for the iterative solver is the introduction
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Machine-learning-based data recovery and its contribution to seismic acquisition: Simultaneous application of deblending, trace reconstruction, and low-frequency extrapolation Geophysics (IF 2.609) Pub Date : 2021-02-23 Shotaro Nakayama; Gerrit Blacquière
Acquisition of incomplete data, i.e., blended, sparsely sampled, and narrowband data, allows for cost-effective and efficient field seismic operations. This strategy becomes technically acceptable, provided that a satisfactory recovery of the complete data, i.e., deblended, well-sampled, and broadband data, is attainable. Hence, we explore a machine-learning approach that simultaneously performs suppression
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Determination of the time-dependent moment tensor using time reverse imaging Geophysics (IF 2.609) Pub Date : 2021-02-23 Claudia Finger; Erik H. Saenger
We have developed an approach to determine the time-dependent moment tensor and the origin time in addition to commonly derived locations of seismic events using time reverse imaging (TRI). It is crucial to locate and characterize the occurring microseismicity without making a priori assumptions about the sources to fully understand the subsurface processes inducing seismicity. Low signal-to-noise
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PS energy imaging condition for microseismic data — Part 2: Sensitivity analysis in 3D anisotropic media Geophysics (IF 2.609) Pub Date : 2021-02-23 Can Oren; Jeffrey Shragge
In microseismic monitoring, obtaining reliable information about event properties, such as the location, origin time, and moment-tensor components, is critical for evaluating the success of fluid-injection programs. Elastic wavefield-based migration approaches can robustly image microseismic sources by extrapolating data through an earth model and evaluating an imaging condition. The success of these
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PS energy imaging condition for microseismic data — Part 1: Theory and applications in 3D isotropic media Geophysics (IF 2.609) Pub Date : 2021-02-23 Can Oren; Jeffrey Shragge
Accurately estimating event locations is of significant importance in microseismic investigations because this information greatly contributes to the overall success of hydraulic-fracturing monitoring programs. Full-wavefield time-reverse imaging (TRI) using one or more wave-equation imaging conditions offers an effective methodology for locating surface-recorded microseismic events. Although, to be
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Bayesian facies inversion on a partially dolomitized isolated carbonate platform: A case study from Central Luconia Province, Malaysia Geophysics (IF 2.609) Pub Date : 2021-02-23 George Ghon; Dario Grana; Eugene C. Rankey; Gregor T. Baechle; Florian Bleibinhaus; Xiaozheng Lang; Leandro Passos de Figueiredo; Michael C. Poppelreiter
We have developed a case study of geophysical reservoir characterization in which we use elastic inversion and probabilistic prediction to estimate nine carbonate lithofacies and the associated porosity distribution. The study focuses on an isolated carbonate platform of middle Miocene age, offshore Sarawak in Malaysia that has been partly dolomitized — a process that increased the porosity and permeability
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Joint and constrained inversion of magnetic and gravity data: A case history from the McArthur River area, Canada Geophysics (IF 2.609) Pub Date : 2021-02-22 Mehrdad Darijani; Colin G. Farquharson; Peter G. Lelièvre
Magnetic and gravity data are used in the early stages of exploration for uranium deposits in the Athabasca Basin of Canada, just as for many other mineral exploration scenarios. Uranium mineralization in the Athabasca Basin is located where faults in the basement intersect the unconformity between the basement and the overlying sandstones. The gravity and magnetic data are dominated by signatures
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Implementation of the Marchenko multiple elimination algorithm Geophysics (IF 2.609) Pub Date : 2021-02-19 Jan Thorbecke; Lele Zhang; Kees Wapenaar; Evert Slob
The Marchenko multiple elimination (MME) and transmission compensation schemes retrieve primary reflections in the two-way traveltime domain without model information or using adaptive subtraction. Both schemes are derived from projected Marchenko equations and are similar to each other, but they use different time-domain truncation operators. The MME scheme retrieves a new data set without internal
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Advanced monopole and dipole sonic log data processing — Part 1: Real time Geophysics (IF 2.609) Pub Date : 2021-02-19 Ruijia Wang; Brian Hornby; Kristoffer Walker; Chung Chang; Gary Kainer; John Granville; Baichun Sun; JoonShik Kim
Real-time open-hole wireline sonic logging data processing becomes a nontrivial task to accurately, automatically, and efficiently evaluate the compressional and shear slowness of a borehole rock formation when human interaction is not possible and the signal processing time is limited to the elapsed time between different transmitter excitations. To address real-time sonic data processing challenges
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Deep-seismic-prior-based reconstruction of seismic data using convolutional neural networks Geophysics (IF 2.609) Pub Date : 2021-02-18 Qun Liu; Lihua Fu; Meng Zhang
The reconstruction of seismic data with missing traces has been a long-standing issue in seismic data processing. Deep learning (DL) has emerged as a popular tool for seismic interpolation; it learns priors from training data sets of incomplete/complete data pairs. However, these DL methods are restricted to training data because they are supervised. When the features of the testing and training data
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Variable-order optimal implicit finite-difference schemes for explicit time-marching solutions to wave equations Geophysics (IF 2.609) Pub Date : 2021-02-18 Wenhua Wang; Xiaotao Wen; Chao Tang; Bo Li; Lei Li; Wei Wang
The time-space-domain finite-difference method (FDM) is widely used in forward modeling of wave equations. Conventional explicit FDMs (EFDMs) (with high order in space and the second order in time) would result in apparent temporal and spatial dispersion for high frequencies and large time steps. Moreover, the saturation effect of Taylor expansion seriously restricts the improvement of bandwidth coverage
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Unsupervised domain adaptation using maximum mean discrepancy optimization for lithology identification Geophysics (IF 2.609) Pub Date : 2021-02-18 Ji Chang; Jing Li; Yu Kang; Wenjun Lv; Ting Xu; Zerui Li; Wei Xing Zheng; Hongwei Han; Haining Liu
Lithology identification plays an essential role in geologic exploration and reservoir evaluation. In recent years, machine-learning-based logging lithology identification has received considerable attention due to its ability to fit complex models. Existing work develops machine-learning models under the assumption that the data gathered from different wells are from the same probability distribution
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Reciprocity-gap misfit functional for distributed acoustic sensing, combining data from passive and active sources Geophysics (IF 2.609) Pub Date : 2021-02-05 Florian Faucher; Maarten V. de Hoop; Otmar Scherzer
Quantitative imaging of subsurface earth properties in elastic media is performed from distributed acoustic sensing data. A new misfit functional based upon the reciprocity gap is designed, taking crosscorrelations of displacement and strain, and these products further associate an observation with a simulation. In comparison with other misfit functionals, this functional has the advantage of only
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Simulated annealing velocity analysis: Automating the picking process Geophysics (IF 2.609) Pub Date : 2021-02-15 Danilo Velis
We have developed an automated method for velocity picking that allows us to estimate appropriate velocity functions for the normal moveout correction of common-depth-point (CDP) gathers, valid for either hyperbolic or nonhyperbolic trajectories. In the hyperbolic velocity analysis case, the process involves the simultaneous search (picking) of a certain number of time-velocity pairs in which the semblance
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Combination of the common reflection surface-based prestack data regularization and reverse time migration: Application to real land data Geophysics (IF 2.609) Pub Date : 2021-02-15 German Garabito; Paul L. Stoffa; Yuri S. F. Bezerra; João L. Caldeira
The application of reverse time migration (RTM) to land seismic data is still a great challenge due to its low quality, low signal-to-noise ratio, irregular spatial sampling, acquisition gaps, and missing traces. Therefore, prior to the application of this kind of depth migration, the input prestack data must be judiciously preconditioned; that is, it must be interpolated, regularized, and enhanced
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3D forward modeling of controlled-source electromagnetic data based on the radiation boundary method Geophysics (IF 2.609) Pub Date : 2021-02-15 Rahul Dehiya
I have developed an efficient 3D forward modeling algorithm based on radiation boundary conditions for controlled-source electromagnetic data. The proposed algorithm derives computational efficiency from a stretch-free discretization, air-free computational domain, and a better initial guess for an iterative solver. A technique for estimation of optimum grid stretching for multifrequency modeling of
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Prestack seismic data reconstruction and denoising by orientation-dependent tensor decomposition Geophysics (IF 2.609) Pub Date : 2021-02-11 Quézia Cavalcante; Milton J. Porsani
Multidimensional seismic data reconstruction and denoising can be achieved by assuming noiseless and complete data as low-rank matrices or tensors in the frequency-space domain. We have adopted a simple and effective approach to interpolate prestack seismic data that explores the low-rank property of multidimensional signals. The orientation-dependent tensor decomposition represents an alternative
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Near-surface full-waveform inversion in a transmission surface-consistent scheme Geophysics (IF 2.609) Pub Date : 2021-02-15 Daniele Colombo; Ernesto Sandoval-Curiel; Diego Rovetta; Apostolos Kontakis
Land seismic velocity modeling is a difficult task largely related to the description of the near-surface complexities. Full-waveform inversion (FWI) is the method of choice for achieving high-resolution velocity mapping, but its application to land seismic data faces difficulties related to the complex physics, unknown and spatially varying source signatures, and low signal-to-noise ratio (S/N) in
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Handling gaps in acquisition geometries — Improving Marchenko-based imaging using sparsity-promoting inversion and joint inversion of time-lapse data Geophysics (IF 2.609) Pub Date : 2021-02-11 Claudia Haindl; Matteo Ravasi; Filippo Broggini
Marchenko focusing and imaging are novel methods for correctly handling multiple scattered energy while processing seismic data. However, strict requirements in the acquisition geometry, specifically the colocation of sources and receivers as well as dense and regular sampling, currently constrain their practical applicability. We have reformulated the Marchenko equations to handle the case in which
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A one-step Bayesian inversion framework for 3D reservoir characterization based on a Gaussian mixture model — A Norwegian Sea demonstration Geophysics (IF 2.609) Pub Date : 2021-02-11 Torstein Fjeldstad; Per Avseth; Henning Omre
We have developed a one-step approach for Bayesian prediction and uncertainty quantification of lithology/fluid classes, petrophysical properties, and elastic attributes conditional on prestack 3D seismic amplitude-variation-with-offset data. A 3D Markov random field prior model is assumed for the lithology/fluid classes to ensure spatially coupled lithology/fluid class predictions in the lateral and
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Time-lapse detection using raypath interferometry Geophysics (IF 2.609) Pub Date : 2021-02-15 David C. Henley; Donald C. Lawton
The objective of most seismic time-lapse studies is to detect rock-property changes in a subsurface formation caused by fluid withdrawal or injection, often by comparing seismic reflection images of the subsurface before and after the operation. Because rock-property changes can affect the amplitudes of seismic reflection events associated with the boundaries of the formation, amplitude anomalies are
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Testing of a permanent orbital surface source and distributed acoustic sensing for monitoring of unconventional reservoirs: Preliminary results from the Eagle Ford Shale Geophysics (IF 2.609) Pub Date : 2021-02-15 Feng Cheng; Julia Correa; Shan Dou; Barry Freifeld; Todd Wood; Kurt Nihei; Dante Guerra; Jens Birkholzer; Benxin Chi; Jonathan Ajo-Franklin
The effective monitoring of hydraulic fracturing in unconventional oil and gas production requires tools to quantify elastic property variations even in the absence of microseismic activity. To track the subtle time-lapse variations in reservoir properties during such activities, monitoring techniques with high repeatability and high resolution, spatially and temporally, are required. Distributed acoustic
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Seismic horizon extraction with dynamic programming Geophysics (IF 2.609) Pub Date : 2021-02-11 Shangsheng Yan; Xinming Wu
Horizon picking is a fundamental and crucial step for seismic interpretation, but it remains a time-consuming task. Although various automatic methods have been developed to extract horizons in seismic images, most of them may fail to pick horizons across discontinuities such as faults and noise. To obtain more accurate horizons, we have developed a dynamic programming algorithm to efficiently refine
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Disjoint interval bound constraints using the alternating direction method of multipliers for geologically constrained inversion: Application to gravity data Geophysics (IF 2.609) Pub Date : 2021-02-11 Vitaliy Ogarko; Jérémie Giraud; Roland Martin; Mark Jessell
To reduce uncertainties in reconstructed images, geologic information must be introduced in a numerically robust and stable way during the geophysical data inversion procedure. In the context of potential (gravity) data inversion, it is important to bound the physical properties by providing probabilistic information on the number of lithologies and ranges of values of possibly existing related rock
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Multiwindow weighted stacking of surface-wave dispersion Geophysics (IF 2.609) Pub Date : 2021-02-11 Sylvain Pasquet; Wei Wang; Po Chen; Brady A. Flinchum
Surface-wave methods are classically used to characterize shear (S-) wave velocities (VS) of the shallow subsurface through the inversion of dispersion curves. When targeting 2D shallow structures with sharp lateral heterogeneity, windowing and stacking techniques can be implemented to provide a better description of VS lateral variations. These techniques, however, suffer from the trade-off between
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The effect of power lines on time-domain airborne electromagnetic data Geophysics (IF 2.609) Pub Date : 2021-02-11 Seogi Kang; Noah Dewar; Rosemary Knight
The acquisition of airborne electromagnetic (AEM) data colocated with water well data provides an essential data set for constructing an accurate rock-physics relationship between resistivity from AEM and lithology from wells. Results from an AEM survey in Butte and Glenn Counties, California, USA, where 41 water wells are located within 100 m of the AEM flight lines, provide a unique opportunity to
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Anisotropic dynamic and static mechanical properties of organic-rich shale: The influence of stress Geophysics (IF 2.609) Pub Date : 2021-02-11 Yang Wang; Luanxiao Zhao; De-hua Han; Abhijit Mitra; Hui Li; Samir Aldin
Understanding the relationship between dynamic and static mechanical properties of organic-rich shales is crucial for successful in situ stress profile prediction and hydraulic fracturing stimulation in unconventional reservoirs. However, the relationship between dynamic and static properties remains ambiguous, considering the complex rock microstructure and subsurface stress environment. We have reported
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Magnetic and gravity investigation of kimberlites in north-central Botswana Geophysics (IF 2.609) Pub Date : 2021-02-15 Kitso Matende; Kevin Mickus
The Orapa kimberlite field of Botswana is one of the world’s major diamond producing regions. Within this field, there are several small kimberlite pipes that have not been completely explored in terms of their lateral extent, depth, and diamond potential. Two such pipes, BK54 and BK55, were found during a ground gravity and magnetic survey, and subsequent drilling confirmed the presence of kimberlite
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Minibatch least-squares reverse time migration in a deep-learning framework Geophysics (IF 2.609) Pub Date : 2021-02-09 Janaki Vamaraju; Jeremy Vila; Mauricio Araya-Polo; Debanjan Datta; Mohamed Sidahmed; Mrinal K. Sen
Migration techniques are an integral part of seismic imaging workflows. Least-squares reverse time migration (LSRTM) overcomes some of the shortcomings of conventional migration algorithms by compensating for illumination and removing sampling artifacts to increase spatial resolution. However, the computational cost associated with iterative LSRTM is high and convergence can be slow in complex media
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Acoustic fields for monopole logging while drilling with an eccentric collar Geophysics (IF 2.609) Pub Date : 2021-02-04 Yunjia Ji; Xiao He; Hao Chen; Xiuming Wang; Hailan Zhang
The acoustic problem of an eccentric drill collar in a fluid-filled borehole has been of interest in the field of acoustic logging while drilling (ALWD) in recent years. To reduce the effects of tool eccentricity on ALWD measurements, studies on acoustic responses under such conditions are essential. This study therefore has developed an analytical method to investigate borehole wavefields with an
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Data-driven multichannel poststack seismic impedance inversion via patch-ordering regularization Geophysics (IF 2.609) Pub Date : 2021-02-05 Lingqian Wang; Hui Zhou; Wenling Liu; Bo Yu; Huili He; Hanming Chen; Ning Wang
Seismic acoustic impedance inversion plays an important role in reservoir prediction. However, single-trace inversion methods often suffer from spatial discontinuities and instability due to poor-quality seismic records with spatially variable signal-to-noise ratios or missing traces. The specified hyperparameters for seismic inversion cannot be suitable to all seismic traces and subsurface structures
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A novel time-domain polarization filter based on a correlation matrix analysis Geophysics (IF 2.609) Pub Date : 2021-02-05 Maher Nasr; Bernard Giroux; J. Christian Dupuis
Polarization filters (PFs) are widely used for denoising seismic data. These filters are applied in the fields of seismology, microseismic monitoring, vertical seismic profiling, and subsurface imaging. They are primarily useful to suppress ground roll in seismic reflection data and enhance P- and S-wave arrivals. Traditional implementations of PFs involved the analysis of the covariance matrix or
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Automatic velocity picking from semblances with a new deep-learning regression strategy: Comparison with a classification approach Geophysics (IF 2.609) Pub Date : 2021-02-05 Wenlong Wang; George A. McMechan; Jianwei Ma; Fei Xie
The physical basis, parameterization, and assumptions involved in root-mean-square (rms) velocity estimation have not significantly changed since they were first developed. However, these three aspects are all good targets for novel application of the recent emergence of machine learning (ML). Therefore, it is useful at this time to provide a tutorial overview of two state-of-the-art ML implementations;
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Prestack diffraction separation in the common virtual source gather Geophysics (IF 2.609) Pub Date : 2021-02-05 Chuangjian Li; Jingtao Zhao; Suping Peng; Xiaoqin Cui
Diffractions are the seismic responses of subsurface small-scale geologic discontinuities or inhomogeneities, whose energy is much weaker than that of reflections. To eliminate the masking effect of strong reflections on weak diffractions, a prestack diffraction separation method is proposed based on the common virtual source gather (CVSG) and the median filter. The reflection generated from a reflector
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Simultaneous inversion for S-wave velocity and density from the SV-SV wave Geophysics (IF 2.609) Pub Date : 2021-02-05 Feng Zhang
Knowledge of the S-wave velocity (VS) and density (ρ) is essential for oil and gas reservoir detection and characterization. However, reliable recovery of both parameters, especially density, from the reflected PP-wave data is a difficult issue because this inverse problem is highly ill-conditioned. The reflected SV-SV wave is easier to process than the PS-wave, and it can provide better estimates
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Diffraction-angle filtering of gradient for acoustic full-waveform inversion Geophysics (IF 2.609) Pub Date : 2021-02-04 Ju-Won Oh; Jiubing Cheng; Dong-Joo Min
Seismic full-waveform inversion (FWI) estimates subsurface velocity structures by reducing data misfit between observed and modeled data. Simultaneous matching of transmitted and reflected waves in seismic FWI causes different updates of different wavenumber components of a given model depending on the diffraction angle between incident and diffracted rays. Motivated by the inverse-scattering imaging
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Central-difference time-lapse 4D seismic full-waveform inversion Geophysics (IF 2.609) Pub Date : 2021-02-04 Wei Zhou; David Lumley
Repeated seismic surveys contain valuable information regarding time-lapse (4D) changes in the subsurface. Full-waveform inversion (FWI) of seismic data can provide high-resolution estimates of 4D change. We have adopted a new time-domain 2D acoustic time-lapse FWI method based on the central-difference scheme with higher order mathematical accuracy and reasonable computational cost. The method is
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Robust estimation of primaries by sparse inversion and Marchenko equation-based workflow for multiple suppression in the case of a shallow water layer and a complex overburden: A 2D case study in the Arabian Gulf Geophysics (IF 2.609) Pub Date : 2021-02-05 Myrna Staring; Marcin Dukalski; Mikhail Belonosov; Rolf H. Baardman; Jewoo Yoo; Rob F. Hegge; Roald van Borselen; Kees Wapenaar
Suppression of surface-related and internal multiples is an outstanding challenge in seismic data processing. The former is particularly difficult in shallow water, whereas the latter is problematic for targets buried under complex, highly scattering overburdens. We have developed a two-step, amplitude- and phase-preserving, inversion-based workflow that addresses these problems. We apply robust estimation
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Micromechanics-based rock-physics model for inorganic shale Geophysics (IF 2.609) Pub Date : 2021-02-05 Igor Sevostianov; Lev Vernik
The full set of transversely isotropic elastic stiffness constants of inorganic shale (mudrock with total organic carbon less than 1.5%) can be successfully modeled and, therefore, predicted based on the mineral composition, mineral stiffnesses, clay platelet orientation distribution function, and microgeometry of the pore space. A fundamentally novel concept drawing from the Maxwell homogenization
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Mechanical properties of grain contacts in unconsolidated sands Geophysics (IF 2.609) Pub Date : 2021-02-05 Colin M. Sayers
Unconsolidated sands provide zones of high porosity and permeability important for freshwater aquifers, hydrocarbon production, and CO2 sequestration. An understanding of the acoustics of unconsolidated sands enables the characterization of such formations using ultrasonics, borehole acoustics, and seismic methods. Inversion of ultrasonic compressional and shear velocities measured for unloading as
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Attenuation and dispersion of P-waves in fluid-saturated porous rocks with a distribution of coplanar cracks — Scattering approach Geophysics (IF 2.609) Pub Date : 2021-02-05 Yongjia Song; Jun Wang; Hengshan Hu; Bo Han
Wave-induced fluid flow (WIFF) between cracks and micropores is one of the major mechanisms causing attenuation and dispersion within seismic frequency ranges. Previous non-interaction-approximation (NIA) models often assume that the distribution of cracks is dilute, neglecting the influences of interacting cracks on dispersion and attenuation. To overcome this restriction, we have investigated the
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A geomechanical correction for time-lapse amplitude variation with offset Geophysics (IF 2.609) Pub Date : 2021-02-05 Colin MacBeth; Samarth Bachkheti
Accurate inversion of time-lapse amplitude variation with offset (AVO) to reservoir pressure change requires knowledge of strain/stress changes in the reservoir and overburden. These geomechanical effects have not been taken into account in previous studies. We have determined that there are three contributions of importance that must be included in the AVO equations: a density term in the reservoir
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Microseismic moment-tensor inversion and sensitivity analysis in vertically transverse isotropic media Geophysics (IF 2.609) Pub Date : 2021-02-05 Han Li; Xu Chang; Xiao-Bi Xie; Yibo Wang
Through the study of microseismic focal mechanisms, information such as fracture orientation, event magnitude, and in situ stress status can be quantitatively obtained, thus providing a reliable basis for unconventional oil and gas exploration. Most source inversion methods assume that the medium is isotropic. However, hydraulic fracturing is usually conducted in sedimentary rocks, which often exhibit
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Estimating the nuclear magnetic resonance surface relaxivity of Eocene sandstones: A comparison of different approaches Geophysics (IF 2.609) Pub Date : 2021-02-05 Zeyu Zhang; Andreas Weller
Nuclear magnetic resonance (NMR) relaxometry typically involves the analysis of a relaxation time distribution. The surface relaxivity (ρ) is the key parameter that relates the relaxation time to the pore radius. Only a good estimate of the surface relaxivity enables a reliable determination of the pore radius distribution in a rock or sediment sample. A wide variety of approaches for the estimation
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An approximate inversion scheme for surface-borehole electromagnetic in the presence of steel casing: 1D implementation Geophysics (IF 2.609) Pub Date : 2021-02-04 Nestor H. Cuevas
I have developed an approximate inversion scheme for surface-borehole electromagnetic data. The method aims at reducing the computational burden arising by the fine discretization required to accurately solve for the field distribution in the full complexity of the borehole system together with the reservoir medium. I first analyze numerical simulations of the surface-borehole response performed for
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Attenuation methods for quantifying gas saturation in organic-rich shale and tight gas formations Geophysics (IF 2.609) Pub Date : 2021-02-05 Qiaomu Qi; Li-Yun Fu; Jixin Deng; Junxin Cao
Quantitative interpretation of waveform attenuation for determining petrophysical properties remains one of the most challenging problems associated with rock physics. In this study, two effective methods are proposed to compute gas saturation in organic-rich shale and tight gas formations from full-waveform sonic attenuations. We first extract compressional (P)- and shear (S)-wave attenuations from
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Using resistivity data to study the waterflooding process: A case study in tight sandstone reservoirs of the Ordos Basin, China Geophysics (IF 2.609) Pub Date : 2021-02-05 Zhihao Jiang; Jinhua Fu; Gaoren Li; Zhiqiang Mao; Peiqiang Zhao
Water injection is one of the most common methods used to enhance the oil recovery of reservoirs with low permeability and strong heterogeneity. However, with the injection of water in the production process, the formation water salinity, oil saturation, and the distribution of the residual oil in the reservoir are altered, causing difficulties in the evaluation of the flooded layers. Consequently
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Anisotropic elastic finite-difference modeling of sources and receivers on Lebedev grids Geophysics (IF 2.609) Pub Date : 2021-02-05 Erik F. M. Koene; Johan O. A. Robertsson; Fredrik Andersson
The Lebedev grid finite-difference (FD) method allows modeling of anisotropic elastic-wave propagation. On Lebedev grids, erroneous point-source excitations can create spurious (nonphysical) waves. The only known remedy for such artifacts in the literature is the Lisitsa-Vishnevsky method. This method uses a distributed array to create point sources and point receivers on the FD grid. However, the
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Quantifying hydraulically induced fracture height and density from rapid time-lapse distributed acoustic sensing vertical seismic profile data Geophysics (IF 2.609) Pub Date : 2021-02-05 Xiaomin Zhao; Mark E. Willis; Tanya Inks; Glenn A. Wilson
Several recent studies have advanced the use of time-lapse distributed acoustic sensing vertical seismic profile data in horizontal wells for determining hydraulically stimulated fracture properties. Hydraulic fracturing in a horizontal well typically generates vertical fractures in the rock medium around each stage. We have modeled the hydraulically stimulated formation with vertical fracture sets
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Efficient acoustic scalar wave equation modeling in VTI media Geophysics (IF 2.609) Pub Date : 2021-01-29 Yury Nikonenko; Marwan Charara
We have developed a new approach for acoustic wave modeling in transversely isotropic media with a vertical axis of symmetry. This approach is based on using a pure acoustic wave equation derived from the basic physical laws — Hooke’s law and the equation of motion. We find that the conventional equation noted as a pure quasi-P-wave equation computes only one stress component. In our approach, there
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Wave-equation time migration Geophysics (IF 2.609) Pub Date : 2021-01-29 Sergey Fomel; Harpreet Kaur
Time migration, as opposed to depth migration, suffers from two well-known shortcomings: (1) approximate equations are used for computing Green’s functions inside the imaging operator and (2) in case of lateral velocity variations, the transformation between the image-ray coordinates and the Cartesian coordinates is undefined in places where the image rays cross. We have found that the first limitation
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This issue of Geophysics Geophysics (IF 2.609) Pub Date : 2021-01-29
In this article, the Editor of Geophysics provides an overview of all technical articles in this issue of the journal.
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Integrated geophysical imaging of rare earth element-bearing iron oxide-apatite deposits in the Eastern Adirondack Highlands, New York Geophysics (IF 2.609) Pub Date : 2021-01-22 Anjana K. Shah; Ryan D. Taylor; Gregory J. Walsh; Jeffrey D. Phillips
The eastern Adirondack Highlands of northern New York host dozens of iron oxide-apatite (IOA) deposits containing magnetite and rare earth element (REE)-bearing apatite. We use new aeromagnetic, aeroradiometric, ground gravity, and sample petrophysical and geochemical data to image and understand these deposits and their geologic framework. Aeromagnetic total field data reflect highly magnetic leucogranite
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Interferometric redatuming by deconvolution and correlation-based focusing Geophysics (IF 2.609) Pub Date : 2021-01-27 Diego F. Barrera; Joerg Schleicher; Joeri Brackenhoff
Seismic interferometry is a method used to calculate wavefields for sources and receivers that are located where only sources or only receivers are available. There are correlation- or deconvolution-based interferometric methods that can be used to reposition the seismic array from the earth’s surface to an arbitrary datum at depth. Based on the one-way reciprocity theorems of convolution and correlation
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Observing maturing source rocks on seismic reflection data Geophysics (IF 2.609) Pub Date : 2021-01-27 Tim Matava; Robert G. Keys; Sverre E. Ohm; Stefano Volterrani
Hydrocarbon generation in a source rock is a complex, irreversible phase change that occurs when a source rock is heated during burial to change the phase to a fluid. The fluid density is less than the kerogen density; therefore, in a closed or partially closed system, the volume of the pore space occupied by fluids increases. Burial also increases the effective stress, which leads to compaction and
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Deep learning a poroelastic rock-physics model for pressure and saturation discrimination Geophysics (IF 2.609) Pub Date : 2021-01-27 Wolfgang Weinzierl; Bernd Wiese
Determining saturation and pore pressure is relevant for hydrocarbon production as well as natural gas and CO2 storage. In this context, seismic methods provide spatially distributed data used to determine gas and fluid migration. A method is developed that allows the determination of saturation and reservoir pressure from seismic data, more accurately from the rock-physics attributes of velocity,
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Robust damped rank-reduction method for simultaneous denoising and reconstruction of 5D seismic data Geophysics (IF 2.609) Pub Date : 2021-01-21 Yapo Abolé Serge Innocent Oboué; Wei Chen; Hang Wang; Yangkang Chen
We have developed a new method for simultaneous denoising and reconstruction of 5D seismic data corrupted by random noise and missing traces. Several algorithms have been developed for seismic data restoration based on rank-reduction (RR) methods. More recently, a damping operator has been introduced into the conventional truncated singular-value decomposition (TSVD) formula to further remove residual
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