An efficient local operator-based Q-compensated reverse time migration algorithm with multistage optimization

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. S249-S259 ◽  
Author(s):  
Tong Zhou ◽  
Wenyi Hu ◽  
Jieyuan Ning
Keyword(s):  
Seismic Attenuation ◽  
Depth Information ◽  
Frequency Noise ◽  
Processing Unit ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Time Migration ◽  
Imaging Results

Most existing [Formula: see text]-compensated reverse time migration ([Formula: see text]-RTM) algorithms are based on pseudospectral methods. Because of the global nature of pseudospectral operators, these methods are not ideal for efficient parallelization, implying that they may suffer from high computational cost and inefficient memory usage for large-scale industrial problems. In this work, we reported a novel [Formula: see text]-RTM algorithm — the multistage optimized [Formula: see text]-RTM method. This [Formula: see text]-RTM algorithm uses a finite-difference method to compensate the amplitude and the phase simultaneously by uniquely combining two techniques: (1) a negative [Formula: see text] method for amplitude compensation and (2) a multistage dispersion optimization technique for phase correction. To prevent high-frequency noise from growing exponentially and ruining the imaging results, we apply a finite impulse response low-pass filter using the Kaiser window. The theoretical analyses and numerical experiments demonstrate that this [Formula: see text]-RTM algorithm precisely recovers the decayed amplitude and corrects the distorted phase caused by seismic attenuation effects, and hence produces higher resolution subsurface images with the correct structural depth information. This new method performs best in the frequency range of 10–70 Hz. Compared with pseudospectral [Formula: see text]-RTM methods, this [Formula: see text]-RTM approach offers nearly identical imaging quality. Based on local numerical differential operators, this [Formula: see text]-RTM method is very suitable for parallel computing and graphic processing unit implementation, an important feature for large 3D seismic surveys.

Viscoacoustic reverse time migration of joint primaries and different-order multiples

Geophysics ◽  
2020 ◽  
Vol 85 (2) ◽  
pp. S71-S87
Author(s):  
Yingming Qu ◽  
Jinli Li ◽  
Zhe Guan ◽  
Zhenchun Li
Keyword(s):  
Vertical Direction ◽  
Seismic Attenuation ◽  
Frequency Noise ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Sea Bottom ◽  
Multiple Imaging ◽  
Propagation Paths ◽  
Different Order

Compared to primary arrivals, multiples have longer propagation paths and smaller reflection angles, leading to a wider illumination area in the horizontal direction and higher resolution in the vertical direction. Hence, it is better to make full use of the multiples rather than suppressing them. However, seismic attenuation exists widely in the subsurface medium, especially directly below the deep sea bottom. Therefore, to compensate for the attenuation effect during multiple imaging, we have developed a viscoacoustic reverse time migration (RTM) method of different-order multiples. Following the multiple propagation paths, we compensate for the attenuation during source wavefield forward propagation and receiver backward propagation, and we introduce a regularization operator to automatically eliminate the exponential high-frequency noise during the attenuation compensation process. Taking advantage of the full wavefield information, we jointly use the different-order multiples and primaries when implementing viscoacoustic RTM. In numerical examples, we validate the viscoacoustic RTM of different-order multiples in a three-layer attenuation model and an attenuating Sigsbee2B model. Our results suggest that our method can image the models using different-order multiples separately, which suppresses crosstalk artifacts, balances energy, raises resolution, and improves subsalt images dramatically.

Q-compensated reverse-time migration

Geophysics ◽  
2014 ◽  
Vol 79 (3) ◽  
pp. S77-S87 ◽  
Author(s):  
Tieyuan Zhu ◽  
Jerry M. Harris ◽  
Biondo Biondi
Keyword(s):  
Image Resolution ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Pass Filter ◽  
Low Pass Filter ◽  
High Attenuation ◽  
Phase Dispersion ◽  
Time Migration ◽  
Amplitude Attenuation ◽  
Attenuation And Dispersion

Reduced amplitude and distorted dispersion of seismic waves caused by attenuation, especially strong attenuation, always degrades the resolution of migrated images. To improve image resolution, we evaluated a methodology of compensating for attenuation ([Formula: see text]) effects in reverse-time migration ([Formula: see text]-RTM). The [Formula: see text]-RTM approach worked by mitigating the amplitude attenuation and phase dispersion effects in source and receiver wavefields. Source and receiver wavefields were extrapolated using a previously published time-domain viscoacoustic wave equation that offered separated amplitude attenuation and phase dispersion operators. In our [Formula: see text]-RTM implementation, therefore, attenuation- and dispersion-compensated operators were constructed by reversing the sign of attenuation operator and leaving the sign of dispersion operator unchanged, respectively. Further, we designed a low-pass filter for attenuation and dispersion operators to stabilize the compensating procedure. Finally, we tested the [Formula: see text]-RTM approach on a simple layer model and the more realistic BP gas chimney model. Numerical results demonstrated that the [Formula: see text]-RTM approach produced higher resolution images with improved amplitude and phase compared to the noncompensated RTM, particularly beneath high-attenuation zones.

scholarly journals Phaseless Imaging by Reverse Time Migration: Acoustic Waves

2017 ◽  
Vol 10 (1) ◽  
pp. 1-21 ◽  
Author(s):  
Zhiming Chen ◽  
Guanghui Huang
Keyword(s):  
Acoustic Waves ◽  
Numerical Experiments ◽  
Cross Correlation ◽  
Scattering Data ◽  
Imaging Method ◽  
Total Field ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Imaging Results

AbstractWe propose a reliable direct imaging method based on the reverse time migration for finding extended obstacles with phaseless total field data. We prove that the imaging resolution of the method is essentially the same as the imaging results using the scattering data with full phase information when the measurement is far away from the obstacle. The imaginary part of the cross-correlation imaging functional always peaks on the boundary of the obstacle. Numerical experiments are included to illustrate the powerful imaging quality

Near-Borehole Imaging Using Full-Waveform Sonic Data

2021 ◽  
Author(s):  
Hala Alqatari ◽  
Thierry-Laurent Tonellot ◽  
Mohammed Mubarak
Keyword(s):  
Seismic Data ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Full Waveform ◽  
Time Migration ◽  
Imaging Results ◽  
High Resolution Images ◽  
Recorded Data ◽  
The Impact ◽  
Processing Steps

Abstract This work presents a full waveform sonic (FWS) dataset processing to generate high-resolution images of the near-borehole area. The dataset was acquired in a nearly horizontal well over a distance of 5400 feet. Multiple formation boundaries can be identified on the final image and tracked at up to 200 feet deep, along the wellbore's trajectory. We first present a new preprocessing sequence to prepare the sonic data for imaging. This sequence leverages denoising algorithms used in conventional surface seismic data processing to remove unwanted components of the recorded data that could harm the imaging results. We then apply a reverse time migration algorithm to the data at different processing stages to assess the impact of the main processing steps on the final image.

Least-squares reverse time migration via linearized waveform inversion using a Wasserstein metric

Geophysics ◽  
2019 ◽  
Vol 84 (5) ◽  
pp. S411-S423
Author(s):  
Peng Yong ◽  
Jianping Huang ◽  
Zhenchun Li ◽  
Wenyuan Liao ◽  
Luping Qu
Keyword(s):  
Least Squares ◽  
Waveform Inversion ◽  
Synthetic Data ◽  
Gradient Algorithm ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Wasserstein Metric ◽  
Time Migration ◽  
Imaging Results ◽  
Primal Dual

Least-squares reverse time migration (LSRTM), an effective tool for imaging the structures of the earth from seismograms, can be characterized as a linearized waveform inversion problem. We have investigated the performance of three minimization functionals as the [Formula: see text] norm, the hybrid [Formula: see text] norm, and the Wasserstein metric ([Formula: see text] metric) for LSRTM. The [Formula: see text] metric used in this study is based on the dynamic formulation of transport problems, and a primal-dual hybrid gradient algorithm is introduced to efficiently compute the [Formula: see text] metric between two seismograms. One-dimensional signal analysis has demonstrated that the [Formula: see text] metric behaves like the [Formula: see text] norm for two amplitude-varied signals. Unlike the [Formula: see text] norm, the [Formula: see text] metric does not suffer from the differentiability issue for null residuals. Numerical examples of the application of three misfit functions to LSRTM on synthetic data have demonstrated that, compared to the [Formula: see text] norm, the hybrid [Formula: see text] norm and [Formula: see text] metric can accelerate LSRTM and are less sensitive to non-Gaussian noise. For the field data application, the [Formula: see text] metric produces the most reliable imaging results. The hybrid [Formula: see text] norm requires tedious trial-and-error tests for the judicious threshold parameter selection. Hence, the more automatic [Formula: see text] metric is recommended as a robust alternative to the customary [Formula: see text] norm for time-domain LSRTM.

An efficient super-virtual shot encoding scheme for multisource reverse time migration

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. S405-S416
Author(s):  
Xiaofeng Jia ◽  
Wenyang Chen ◽  
Bin Chen
Keyword(s):  
Reverse Time ◽  
Crosstalk Noise ◽  
Reverse Time Migration ◽  
Multiple Sources ◽  
Source Imaging ◽  
Imaging Tool ◽  
Time Migration ◽  
Imaging Result ◽  
Imaging Results ◽  
Simultaneous Source

Reverse time migration (RTM) is a powerful seismic imaging tool that suffers from high computational complexity when dealing with massive data. The simultaneous-shot method can effectively reduce the amount of migration by assembling several sources, although it adds crosstalk noise, which seriously affects the quality of the RTM results. To avoid this problem, we have adopted a time-domain scheme that combines time-delay encoding and amplitude encoding to reduce crosstalk artifacts in simultaneous-source imaging results. This scheme modulates the wavefields of multiple sources to fit the wavefield of a suspended super-virtual shot (SVS), which can eliminate crosstalk artifacts because they are absent in single SVS migration. Numerical examples on a steeply dipping model and the 2D SEG/EAGE salt model show the feasibility of the proposed method. SVS encoding can generate a qualified imaging result and takes less time than plane-wave encoding in the migration process.

Diffraction imaging for fault-karst structure by least-squares reverse time migration

2020 ◽  
pp. 1-40
Author(s):  
Xinru Mu ◽  
Jianping Huang ◽  
Liyun Fu ◽  
Shikai Jian ◽  
Bing Hu ◽  
...  
Keyword(s):  
Least Squares ◽  
Western China ◽  
Small Scale ◽  
Imaging Method ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Imaging Results ◽  
Heterogeneous Structures ◽  
Karst Reservoir

The fault-karst reservoir, which evolved from the deformation and karstification of carbonate rock, is one of the most important reservoir types in western China. Along the deep-seated fault zones, there are a lot widely spread and densely distributed fractures and vugs. The energy of the diffractions generated by heterogeneous structures, such as faults, fractures and vugs, are much weaker than that of the reflections produced by continuous formation interface. When using conventional full wavefield imaging method, the imaging results of continuous layers usually cover small-scale heterogeneities. Given that, we use plane-wave destruction (PWD) filter to separate the diffractions from the full data and image the separated diffractions using least-squares reverse time migration (LSRTM) method. We use several numerical examples to demonstrate that the newly developed diffractions LSRTM (D-LSRTM) can improve the definition of the heterogeneous structures, characterize the configuration and internal structure of the fault-karst structure well and enhance the interpretation accuracy for fault-karst reservoir.

Reverse Time Migration Using the Pseudospectral Time-Domain Algorithm

2016 ◽  
Vol 24 (02) ◽  
pp. 1650005 ◽  
Author(s):  
Jiangang Xie ◽  
Zichao Guo ◽  
Hai Liu ◽  
Qing Huo Liu
Keyword(s):  
Time Domain ◽  
Acoustic Waves ◽  
Fdtd Method ◽  
Pseudospectral Method ◽  
Imaging Method ◽  
Processing Unit ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Eighth Order ◽  
Time Migration

We propose a pre-stack reverse time migration (RTM) seismic imaging method using the pseudospectral time-domain (PSTD) algorithm. Traditional pseudospectral method uses the fast Fourier transform (FFT) algorithm to calculate the spatial derivatives, but is limited by the wraparound effect due to the periodicity assumed in the FFT. The PSTD algorithm combines the pseudospectral method with a perfectly matched layer (PML) for acoustic waves. PML is a highly effective absorbing boundary condition that can eliminate the wraparound effect. It enables a wide application of the pseudospectral method to complex models. RTM based on the PSTD algorithm has advantages in the computational efficiency compared to traditional methods such as the second-order and high order finite difference time-domain (FDTD) methods. In this work, we implement the PSTD algorithm for acoustic wave equation based RTM. By applying the PSTD-RTM method to various seismic models and comparing it with RTM based on the eighth-order FDTD method, we find that PSTD-RTM method has better performance and saves more than 50% memory. The method is suitable for parallel computation, and has been accelerated by general purpose graphics processing unit.

scholarly journals Q-compensated least-squares reverse time migration using low-rank one-step wave extrapolation

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. S271-S279 ◽  
Author(s):  
Junzhe Sun ◽  
Sergey Fomel ◽  
Tieyuan Zhu ◽  
Jingwei Hu
Keyword(s):  
Convergence Rate ◽  
Least Squares ◽  
Seismic Attenuation ◽  
Low Rank ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Attenuation Compensation ◽  
Time Migration ◽  
Rank One ◽  
One Step

Attenuation of seismic waves needs to be taken into account to improve the accuracy of seismic imaging. In viscoacoustic media, reverse time migration (RTM) can be performed with [Formula: see text]-compensation, which is also known as [Formula: see text]-RTM. Least-squares RTM (LSRTM) has also been shown to be able to compensate for attenuation through linearized inversion. However, seismic attenuation may significantly slow down the convergence rate of the least-squares iterative inversion process without proper preconditioning. We have found that incorporating attenuation compensation into LSRTM can improve the speed of convergence in attenuating media, obtaining high-quality images within the first few iterations. Based on the low-rank one-step seismic modeling operator in viscoacoustic media, we have derived its adjoint operator using nonstationary filtering theory. The proposed forward and adjoint operators can be efficiently applied to propagate viscoacoustic waves and to implement attenuation compensation. Recognizing that, in viscoacoustic media, the wave-equation Hessian may become ill-conditioned, we propose to precondition LSRTM with [Formula: see text]-compensated RTM. Numerical examples showed that the preconditioned [Formula: see text]-LSRTM method has a significantly faster convergence rate than LSRTM and thus is preferable for practical applications.

scholarly journals LAGUERRE-GAUSS FILTERS IN REVERSE TIME MIGRATION IMAGE RECONSTRUCTION

2018 ◽  
Vol 35 (2) ◽  
Author(s):  
Juan Guillermo Paniagua Castrillón ◽  
Olga Lucia Quintero Montoya ◽  
Daniel Sierra-Sosa
Keyword(s):  
Cross Correlation ◽  
Synthetic Data ◽  
Low Frequency ◽  
Frequency Noise ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Imaging Condition ◽  
Time Migration ◽  
Migration Imaging ◽  
Gauss Transform

ABSTRACT. Reverse time migration (RTM) solves the acoustic or elastic wave equation by means of the extrapolation from source and receiver wavefield in time. A migrated image is obtained by applying a criteria known as imaging condition. The cross-correlation between source and receiver wavefields is the commonly used imaging condition. However, this imaging condition produces spatial low-frequency noise, called artifacts, due to the unwanted correlation of the diving, head and backscattered waves. Several techniques have been proposed to reduce the artifacts occurrence. Derivative operators as Laplacian are the most frequently used. In this work, we propose a technique based on a spiral phase filter ranging from 0 to 2π, and a toroidal amplitude bandpass filter, known as Laguerre-Gauss transform. Through numerical experiments we present the application of this particular filter on three synthetic data sets. In addition, we present a comparative spectral study of images obtained by the zero-lag cross-correlation imaging condition, the Laplacian filtering and the Laguerre-Gauss filtering, showing their frequency features. We also present evidences not only with simulated noisy velocity fields but also by comparison with the model velocity field gradients that this method improves the RTM images by reducing the artifacts and notably enhance the reflective events. Keywords: Laguerre-Gauss transform, zero-lag cross-correlation, seismic migration, imaging condition. RESUMO. A migração reversa no tempo (RTM) resolve a equação de onda acústica ou elástica por meio da extrapolação a partir do campo de onda da fonte e do receptor no tempo. Uma imagem migrada é obtida aplicando um critério conhecido como condição de imagem. A correlação cruzada entre campos de onda de fonte e receptor é a condição de imagem comumente usada. No entanto, esta condição de imagem produz ruído espacial de baixa frequência, chamados artefatos, devido à correlação indesejada das ondas de mergulho, cabeça e retrodifusão. Várias técnicas têm sido propostas para reduzir a ocorrência de artefatos. Operadores derivados como Laplaciano são os mais utilizados. Neste trabalho, propomos uma técnica baseada em um filtro de fase espiral que varia de 0 a 2π, e um filtro passabanda de amplitude toroidal, conhecido como transformada de Laguerre-Gauss. Através de experimentos numéricos, apresentamos a aplicação deste filtro particular em três conjuntos de dados sintéticos. Além disso, apresentamos um estudo comparativo espectral de imagens obtidas pela condição de imagem de correlação cruzada atraso zero, a filtragem de Laplaciano e a filtragem Laguerre-Gauss, mostrando suas características de frequência. Apresentamos evidências não somente com campos simulados de velocidade ruidosa, mas também por comparação com os gradientes de campo de velocidade do modelo que este método melhora as imagens RTM, reduzindo os artefatos e aumentando notavelmente os eventos reflexivos. Palavras-chave: Transformação de Laguerre-Gauss, correlação cruzada atraso zero, migração sísmica, condição de imagem.

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