Multiarrival Kirchhoff beam migration

Geophysics ◽  
2011 ◽  
Vol 76 (5) ◽  
pp. WB109-WB118 ◽  
Author(s):  
Jonathan Liu ◽  
Gopal Palacharla
Keyword(s):  
Model Updating ◽  
Plane Waves ◽  
Beam Width ◽  
Velocity Model ◽  
Model Complexity ◽  
Depth Migration ◽  
Kirchhoff Migration ◽  
Optimal Beam ◽  
Local Plane ◽  
Gaussian Beam Migration

Kirchhoff-type prestack depth migration is the method most popular for outputting offset gathers for velocity-model updating because of its flexibility and efficiency. However, conventional implementations of Kirchhoff migration use only single arrivals. This limits its ability to image complex structures such as subsalt areas. We use the beam methodology to develop a multiarrival Kirchhoff beam migration. The theory and algorithm of our beam migration are analogs to Gaussian beam migration, but we focus on attaining kinematic accuracy and implementation efficiency. The input wavefield of every common offset panel is decomposed into local plane waves at beam centers on the acquisition surface by local slant stacking. Each plane wave contributes a potential single-arrival in Kirchhoff migration. In this way, our method is able to handle multiarrivals caused by model complexity and, therefore, to overcome the limitation of conventional single-arrival Kirchhoff migration. The choice of the width of the beam is critical to the implementation of beam migration. We provide a formula for optimal beam width that achieves both accuracy and efficiency when the velocity model is reasonably smooth. The resulting structural imaging in subsalt and other structurally complex areas is of better quality than that from single-arrival Kirchhoff migration.

2D anisotropic multicomponent Gaussian-beam migration under complex surface conditions

Geophysics ◽  
2020 ◽  
Vol 85 (2) ◽  
pp. S89-S102 ◽  
Author(s):  
Jianguang Han ◽  
Qingtian Lü ◽  
Bingluo Gu ◽  
Jiayong Yan ◽  
Hao Zhang
Keyword(s):  
Gaussian Beam ◽  
Complex Surface ◽  
Dynamic Features ◽  
Surface Conditions ◽  
Depth Migration ◽  
Surface Areas ◽  
Local Plane ◽  
Gaussian Beam Migration ◽  
Wave Migration ◽  
Irregular Topography

Elastic-wave migration in anisotropic media is a vital challenge, particularly for areas with irregular topography. Gaussian-beam migration (GBM) is an accurate and flexible depth migration technique, which is adaptable for imaging complex surface areas. It retains the dynamic features of the wavefield and overcomes the multivalued traveltimes and caustic problems of Kirchhoff migration. We have extended the GBM method to work for 2D anisotropic multicomponent migration under complex surface conditions. We use Gaussian beams to calculate the wavefield from irregular topography, and we use two schemes to derive the down-continued recorded wavefields. One is based on the local slant stack as in classic GBM, in which the PP- and PS-wave seismic records within the local region are directly decomposed into local plane-wave components from irregular topography. The other scheme does not perform the local slant stack. The Green’s function is calculated with a Gaussian beam summation emitted from the receiver point at the irregular surface. Using the crosscorrelation imaging condition and combining with the 2D anisotropic ray-tracing algorithm, we develop two 2D anisotropic multicomponent Gaussian-beam prestack depth migration (GB-PSDM) methods, i.e., using the slant stack and nonslant stack, for irregular topography. Numerical tests demonstrate that our anisotropic multicomponent GB-PSDM can accurately image subsurface structures under complex topography conditions.

The isochron ray in seismic modeling and imaging

Geophysics ◽  
2004 ◽  
Vol 69 (4) ◽  
pp. 1053-1070 ◽  
Author(s):  
Einar Iversen
Keyword(s):  
Seismic Imaging ◽  
Model Updating ◽  
Velocity Model ◽  
Seismic Modeling ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Geometric Spreading ◽  
Model Independent ◽  
Map Migration ◽  
Upper Level

The isochron, the name given to a surface of equal two‐way time, has a profound position in seismic imaging. In this paper, I introduce a framework for construction of isochrons for a given velocity model. The basic idea is to let trajectories called isochron rays be associated with iso chrons in an way analogous to the association of conventional rays with wavefronts. In the context of prestack depth migration, an isochron ray based on conventional ray theory represents a simultaneous downward continuation from both source and receiver. The isochron ray is a generalization of the normal ray for poststack map migration. I have organized the process with systems of ordinary differential equations appearing on two levels. The upper level is model‐independent, and the lower level consists of conventional one‐way ray tracing. An advantage of the new method is that interpolation in a ray domain using isochron rays is able to treat triplications (multiarrivals) accurately, as opposed to interpolation in the depth domain based on one‐way traveltime tables. Another nice property is that the Beylkin determinant, an important correction factor in amplitude‐preserving seismic imaging, is closely related to the geometric spreading of isochron rays. For these reasons, the isochron ray has the potential to become a core part of future implementations of prestack depth migration. In addition, isochron rays can be applied in many contexts of forward and inverse seismic modeling, e.g., generation of Fresnel volumes, map migration of prestack traveltime events, and generation of a depth‐domain–based cost function for velocity model updating.

True-amplitude Gaussian-beam migration

Geophysics ◽  
2009 ◽  
Vol 74 (2) ◽  
pp. S11-S23 ◽  
Author(s):  
Samuel H. Gray ◽  
Norman Bleistein
Keyword(s):  
Wave Equation ◽  
Gaussian Beam ◽  
Opening Angle ◽  
Amplitude Wave ◽  
Amplitude Variation With Offset ◽  
Imaging Condition ◽  
Depth Migration ◽  
Kirchhoff Migration ◽  
Beam Depth ◽  
Gaussian Beam Migration

Gaussian-beam depth migration and related beam migration methods can image multiple arrivals, so they provide an accurate, flexible alternative to conventional single-arrival Kirchhoff migration. Also, they are not subject to the steep-dip limitations of many (so-called wave-equation) methods that use a one-way wave equation in depth to downward-continue wavefields. Previous presentations of Gaussian-beam migration have emphasized its kinematic imaging capabilities without addressing its amplitude fidelity. We offer two true-amplitude versions of Gaussian-beam migration. The first version combines aspects of the classic derivation of prestack Gaussian-beam migration with recent results on true-amplitude wave-equation migration, yields an expression involving a crosscorrelation imaging condition. To provide amplitude-versus-angle (AVA) information, true-amplitude wave-equation migration requires postmigration mapping from lateral distance (between image location and source location) to subsurface opening angle. However, Gaussian-beam migration does not require postmigration mapping to provide AVA data. Instead, the amplitudes and directions of the Gaussian beams provide information that the migration can use to produce AVA gathers as part of the migration process. The second version of true-amplitude Gaussian-beam migration is an expression involving a deconvolution imaging condition, yielding amplitude-variation-with-offset (AVO) information on migrated shot-domain common-image gathers.

Tomographic velocity model updating for prestack depth migration

1999 ◽  
Author(s):  
Robert Bloor ◽  
Alfonso Gonzalez ◽  
Uwe Albertin ◽  
David Yingst
Keyword(s):  
Model Updating ◽  
Velocity Model ◽  
Prestack Depth Migration ◽  
Depth Migration

Residual stereotomographic inversion

Geophysics ◽  
2006 ◽  
Vol 71 (4) ◽  
pp. E35-E39 ◽  
Author(s):  
Dmitry Neckludov ◽  
Reda Baina ◽  
Evgeny Landa
Keyword(s):  
Model Updating ◽  
Velocity Model ◽  
Model Estimation ◽  
Reflection Point ◽  
Velocity Inversion ◽  
Depth Migration ◽  
Interval Velocity ◽  
Step Procedure ◽  
Tomographic Method ◽  
First Ray

Depth migration requires highly accurate knowledge of the subsurface velocity field. Different traveltime tomographic methods are used for this purpose. Stereotomography is a tomographic method that uses local dip estimates in addition to traveltimes for velocity model estimation. We present a new methodology for velocity model updating. It combines poststack stereotomography and residual moveout velocity inversion. The former is used for initial model construction and the latter for updating the velocity model. Residual inversion is a kind of stereotomographic inversion applied to common reflection point (CRP) gathers after model-based moveout correction. Velocity analysis can be made more efficient by preselecting the traces that contribute to a series of CRP gathers and using only these traces for inversion. The algorithm is defined in a two-step procedure. First, ray tracing from the reflection point for nonzero reflection offsets defines the source and receiver locations of the data traces in the CRS gather. Then these traces are moveout corrected according to the calculated traveltimes and residual moveout is estimated. The interval velocity model is updated by fitting the velocity that minimizes estimated residuals. Application of the proposed technique demonstrates its robustness and reliability for fast and automatic velocity model estimation.

Seismic demigration/migration in the curvelet domain

Geophysics ◽  
2008 ◽  
Vol 73 (2) ◽  
pp. S35-S46 ◽  
Author(s):  
Hervé Chauris ◽  
Truong Nguyen
Keyword(s):  
Input Data ◽  
Plane Waves ◽  
Synthetic Data ◽  
Velocity Model ◽  
Local Velocity ◽  
Data Set ◽  
Migration Operator ◽  
Local Plane ◽  
Seismic Images

Curvelets can represent local plane waves. They efficiently decompose seismic images and possibly imaging operators. We study how curvelets are distorted after demigration followed by migration in a different velocity model. We show that for small local velocity perturbations, the demigration/migration is reduced to a simple morphing of the initial curvelet. The derivation of the expected curvature of the curvelets shows that it is easier to sparsify the demigration/migration operator than the migration operator. An application on a 2D synthetic data set, generated in a smooth heterogeneous velocity model and with a complex reflectivity, demonstrates the usefulness of curvelets to predict what a migrated image would become in a locally different velocity model without the need for remigrating the full input data set. Curvelets are thus well suited to study the sensitivity of a prestack depth-migrated image with respect to the heterogeneous velocity model used for migration.

Gaussian beam reconstruction of seismic data

Geophysics ◽  
2019 ◽  
Vol 84 (5) ◽  
pp. S373-S387 ◽  
Author(s):  
Min Bai ◽  
Juan Wu ◽  
Hua Zhang ◽  
Mi Zhang ◽  
Yangkang Chen
Keyword(s):  
Gaussian Beam ◽  
Seismic Data ◽  
Convex Sets ◽  
Plane Waves ◽  
Reconstruction Algorithm ◽  
Research Field ◽  
Practical Significance ◽  
Reconstruction Performance ◽  
Local Plane ◽  
Gaussian Beam Migration

We have developed a new Gaussian beam reconstruction algorithm using time-domain Gaussian beam (TGB) method to decompose seismic data. The TGB is characterized by a particular arrival time, location, amplitude, orientation, curvature, and extent. TGB decomposition and reconstruction of seismic data are implemented by the plane-wave decomposition (PWD) theory. First, we evaluate the construction principle of TGB, and then we develop the PWD filter to decompose seismic data into local plane waves by estimated dip fields and curvature fields of the seismic records. Next, the local plane waves in terms of TGBs are used to reconstruct seismic data through iteratively minimizing the residual error. Afterward, Gaussian beam depth migration is performed on the reconstructed data. Finally, we analyze the reconstruction results under the circumstance of seismic data with randomly missing traces. Numerical tests indicate that for data with missing traces, the Gaussian beam method obtains better reconstruction performance than the traditional projection onto convex sets method with the same number of iterations. The combination of Gaussian beam seismic data reconstruction and migration extends the research field of Gaussian beam migration, which has an important theoretical and practical significance.

Prestack Gaussian‐beam depth migration

Geophysics ◽  
2001 ◽  
Vol 66 (4) ◽  
pp. 1240-1250 ◽  
Author(s):  
N. Ross Hill
Keyword(s):  
Gaussian Beam ◽  
Velocity Structure ◽  
Saddle Points ◽  
Three Dimensional ◽  
Seismic Energy ◽  
Data Set ◽  
Depth Migration ◽  
Kirchhoff Migration ◽  
Beam Depth ◽  
Gaussian Beam Migration

Kirchhoff migration is the most popular method of three‐dimensional prestack depth migration because of its flexibility and efficiency. Its effectiveness can become limited, however, when complex velocity structure causes multipathing of seismic energy. An alternative is Gaussian beam migration, which is an extension of Kirchhoff migration that overcomes many of the problems caused by multipathing. Unlike first‐arrival and most‐energetic‐arrival methods, which retain only one traveltime, this alternative method retains most arrivals by the superposition of Gaussian beams. This paper presents a prestack Gaussian beam migration method that operates on common‐offset gathers. The method is efficient because the computation of beam superposition isolates summations that do not depend on the seismic data and evaluates these integrals by considering their saddle points. Gaussian beam migration of the two‐dimensional Marmousi test data set demonstrates the method’s effectiveness for structural imaging in a case where there is multipathing of seismic energy.

Fast migration/inversion with multivalued ray fields: Part 2—Applications to the 3D SEG/EAGE salt model

Geophysics ◽  
2004 ◽  
Vol 69 (5) ◽  
pp. 1320-1328 ◽  
Author(s):  
Sheng Xu ◽  
Gilles Lambaré ◽  
Henri Calandra
Keyword(s):  
Three Dimensional ◽  
Velocity Model ◽  
Three Dimensions ◽  
Complex Media ◽  
Depth Migration ◽  
Kirchhoff Migration ◽  
Convenient Approach ◽  
First Arrival ◽  
Subsalt Imaging ◽  
Lateral Variations

Three‐dimensional prestack depth migration is the convenient approach for seismic imaging in the case of strong lateral variations of the velocity. Because of computing limitations, it has been limited to single‐arrival kinematic Kirchhoff migration until recently. This approach fails in the case of complex media characterized by multiarrival traveltimes. We present numerical strategies for extending in three dimensions first‐arrival kinematic Kirchhoff migration to multiarrival quantitative ray‐based migration (preserved amplitude migration). We rely on wavefront construction in a smooth velocity model to compute the multivalued traveltime and amplitude maps, and the CPU efficiency of migration itself is ensured by efficient and robust interpolation or extrapolation strategies. We present an application to the synthetic 3D SEG/EAGE salt model. Taking into account multiarrivals clearly improves subsalt imaging at the price of quite limited computing costs (a 20% increase in our case, with respect to a preserved‐amplitude single‐arrival migration).

Sign in / Sign up

Export Citation Format

Share Document