Diffraction imaging using reverse time migration with poynting vectors

2017 ◽  
Author(s):  
Wenbin Jiang ◽  
Zhiyang Liu ◽  
Jie Zhang
Keyword(s):  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Diffraction Imaging ◽  
Poynting Vectors

Periodic plane-wave least-squares reverse time migration for diffractions

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. S185-S198
Author(s):  
Chuang Li ◽  
Jinghuai Gao ◽  
Zhaoqi Gao ◽  
Rongrong Wang ◽  
Tao Yang
Keyword(s):  
Inverse Problem ◽  
Image Quality ◽  
Plane Wave ◽  
Least Squares ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Diffraction Imaging ◽  
Periodic Plane

Diffraction imaging is important for high-resolution characterization of small subsurface heterogeneities. However, due to geometry limitations and noise distortion, conventional diffraction imaging methods may produce low-quality images. We have adopted a periodic plane-wave least-squares reverse time migration method for diffractions to improve the image quality of heterogeneities. The method reformulates diffraction imaging as an inverse problem using the Born modeling operator and its adjoint operator derived in the periodic plane-wave domain. The inverse problem is implemented for diffractions separated by a plane-wave destruction filter from the periodic plane-wave sections. Because the plane-wave destruction filter may fail to eliminate hyperbolic reflections and noise, we adopt a hyperbolic misfit function to minimize a weighted residual using an iteratively reweighted least-squares algorithm and thereby reduce residual reflections and noise. Synthetic and field data tests show that the adopted method can significantly improve the image quality of subsalt and deep heterogeneities. Compared with reverse time migration, it produces better images with fewer artifacts, higher resolution, and more balanced amplitude. Therefore, the adopted method can accurately characterize small heterogeneities and provide a reliable input for seismic interpretation in the prediction of hydrocarbon reservoirs.

scholarly journals Diffraction imaging using geometric-mean reverse time migration and common-reflection surface

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. S355-S364 ◽  
Author(s):  
Jianhang Yin ◽  
Nori Nakata
Keyword(s):  
Geometric Mean ◽  
Critical Role ◽  
Seismic Exploration ◽  
Small Scale ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Diffracted Waves ◽  
Common Reflection Surface ◽  
Diffraction Imaging

Diffracted waves contain a great deal of valuable information about small-scale subsurface structure such as faults, pinch-outs, karsts, and fractures, which are closely related to hydrocarbon accumulation and production. Therefore, diffraction separation and imaging with high spatial resolution play an increasingly critical role in seismic exploration. We have applied the geometric-mean reverse time migration (GmRTM) method to diffracted waves for imaging only subsurface diffractors based on the difference of the wave phenomena between diffracted and reflected waves. Numerical tests prove the advantages of this method on diffraction imaging with higher resolution as well as fewer artifacts compared to conventional RTM even when we only have a small number of receivers. Then, we developed a workflow to extract diffraction information using a fully data-driven method, called common-reflection surface (CRS), before we applied GmRTM. Application of this workflow indicates that GmRTM further improves the quality of the image by combining with the diffraction-separation technique CRS in the data domain.

An improvement in wavefield extrapolation and imaging condition to suppress reverse time migration artifacts

Geophysics ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. S403-S409 ◽  
Author(s):  
Farzad Moradpouri ◽  
Ali Moradzadeh ◽  
Reynam Pestana ◽  
Reza Ghaedrahmati ◽  
Mehrdad Soleimani Monfared
Keyword(s):  
Weighting Function ◽  
Real Data ◽  
Expansion Method ◽  
Rapid Expansion ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Data Set ◽  
Imaging Condition ◽  
Time Migration ◽  
Poynting Vectors

Reverse time migration (RTM) as a full wave equation method can image steeply dipping structures incorporating all waves without dip limitation. It causes a set of low-frequency artifacts that start to appear for reflection angles larger than 60°. These artifacts are known as the major concern in RTM method. We are first to attempt to formulate a scheme called the leapfrog-rapid expansion method to extrapolate the wavefields and their first derivatives. We have evaluated a new imaging condition, based on the Poynting vectors, to suppress the RTM artifacts. The Poynting vectors information is used to separate the wavefields to their downgoing and upgoing components that form the first part of our imaging condition. The Poynting vector information is also used to calculate the reflection angles as a basis for our weighting function as the second part of the aforementioned imaging condition. Actually, the weighting function is applied to have the most likely desired information and to suppress the artifacts for the angle range of 61°–90°. This is achieved by dividing the angle range to a triplet domain from 61° to 70°, 71° to 80°, and 81° to 90°, where each part has the weight of [Formula: see text], [Formula: see text], and [Formula: see text], respectively. It is interesting to note that, besides suppressing the artifacts, the weighting function also has the capability to preserve crosscorrelation from the real reflecting points in the angle range of 61°–90°. Finally, we tested the new RTM procedure by the BP synthetic model and a real data set for the North Sea. The obtained results indicate the efficiency of the procedure to suppress the RTM artifacts in producing high-quality, highly illuminated depth-migrated image including all steeply dipping geologic structures.

Analysis of direction-decomposed and vector-based elastic reverse time migration using the Hilbert transform

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. S599-S617
Author(s):  
Ting Hu ◽  
Hong Liu ◽  
Xuebao Guo ◽  
Yuxin Yuan ◽  
Zhiyang Wang
Keyword(s):  
Hilbert Transform ◽  
Computational Cost ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Spatial Direction ◽  
Time Migration ◽  
Imaging Artifacts ◽  
Dip Angle ◽  
The Hilbert Transform ◽  
Poynting Vectors

Straightforward implementations of elastic reverse time migration (ERTM) often produce imaging artifacts associated with incorrectly imaged mode conversions, crosstalk, and back-scattered energies. To address these issues, we introduced three approaches: (1) vector-based normalized crosscorrelation imaging conditions (VBNICs), (2) directional separation of wavefields to remove low-wavenumber noise, and (3) postimaging filtering of the dip-angle gathers to eliminate the artifacts caused by nonphysical wave modes. These approaches are combined to create an effective ERTM workflow that can produce high-quality images. Numerical examples demonstrate that, first, VBNICs can produce correct polarities for PP/PS images and can compute migrated dip-angle gathers efficiently by using P/S decomposed Poynting vectors. Second, they achieve improved signal-to-noise and higher resolution when performing up/down decomposition before applying VBNICs, and left/right decomposition enhances steep dips imaging at the computational cost of adding the Hilbert transform to a spatial direction. Third, dip filtering using slope-consistency analysis attenuates the remaining artifacts effectively. An application of the SEG advanced modeling program (SEAM) model demonstrates that our ERTM workflow reduces noise and improves imaging ability for complex geologic areas.

Poststack diffraction imaging using reverse-time migration

2015 ◽  
Vol 64 (1) ◽  
pp. 129-142 ◽  
Author(s):  
Ilya Silvestrov ◽  
Reda Baina ◽  
Evgeny Landa
Keyword(s):  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Diffraction Imaging

Up/down and P/S decompositions of elastic wavefields using complex seismic traces with applications to calculating Poynting vectors and angle-domain common-image gathers from reverse time migrations

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. S181-S194 ◽  
Author(s):  
Wenlong Wang ◽  
George A. McMechan ◽  
Chen Tang ◽  
Fei Xie
Keyword(s):  
Fourier Transforms ◽  
Original Data ◽  
Complex Data ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
S Wave ◽  
Time Migration ◽  
Vsp Data ◽  
Poynting Vectors ◽  
Over Time

Separations of up- and down-going as well as of P- and S-waves are often a part of processing of multicomponent recorded data and propagating wavefields. Most previous methods for separating up/down propagating wavefields are expensive because of the requirement to save time steps to perform Fourier transforms over time. An alternate approach for separation of up-and down-going waves, based on extrapolation of complex data traces is extended from acoustic to elastic, and combined with P- and S-wave decomposition by decoupled propagation. This preserves all the information in the original data and eliminates the need for a Fourier transform over time, thereby significantly reducing the storage cost and improving computational efficiency. Wavefield decomposition is applied to synthetic elastic VSP data and propagating wavefield snapshots. Poynting vectors obtained from the particle velocity and stress fields after P/S and up/down decompositions are much more accurate than those without because interference between the corresponding wavefronts is significantly reduced. Elastic reverse time migration with the P/S and up/down decompositions indicated significant improvement compared with those without decompositions, when applied to elastic data from a portion of the Marmousi2 model.

Reverse time migration angle gathers using Poynting vectors

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. S511-S522 ◽  
Author(s):  
Jia Yan ◽  
Thomas A. Dickens
Keyword(s):  
Poynting Vector ◽  
Computer Time ◽  
Weight Functions ◽  
Seismic Velocities ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Efficient Manner ◽  
Vector Method ◽  
Time Migration ◽  
Poynting Vectors

Angle-domain common-image gathers provide much useful data about the subsurface, such as seismic velocities and amplitude-versus-angle (AVA) information, and they can be manipulated to provide high-quality stacked images. However, the computation of angle gathers for reverse time migration (RTM), the most physically accurate migration algorithm, has proven to be costly in terms of computer time and memory usage. We have developed an algorithm for computing RTM angle gathers in a relatively efficient manner. Our method is based on the construction of the directions of propagation of the source and receiver wavefields, given by the direction of energy flux, known as the Poynting vector. The computation is carried out in the space-time domain, avoiding the need to transform the wavefield to, for example, frequency-wavenumber space, as is needed for methods based on wavefront projection. Given accurate Poynting vectors for source and receiver wavefields, one may compute the local reflection angle and azimuth, as well as the reflector dip and azimuth. An important advantage of our method is that it is based on local direction information at the reflection point, and thus it avoids the loss of resolution and smearing that can occur with some other techniques. A simple implementation of the Poynting-vector method can lead to noisy gathers, with leakage between angle bins, caused by unstable division of the local wavefields. We have developed an efficient technique to mitigate this noise and evaluated examples illustrating the aforementioned smearing issues of the subsurface-offset-based gathers and the improvements in the Poynting-vector gathers arising from our algorithm enhancement. Finally, the use of angle gathers for AVA analysis requires that (relative) amplitudes as a function of angle be correct. To this end, we derive weight functions for computing gathers with the correct AVA behavior. We determine the correctness of these weights by testing them with synthetic data.

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