scholarly journals Kinematics of shot-geophone migration

Geophysics ◽  
2009 ◽  
Vol 74 (6) ◽  
pp. WCA19-WCA34 ◽  
Author(s):  
Christiaan C. Stolk ◽  
Maarten V. de Hoop ◽  
William W. Symes
Keyword(s):  
Velocity Field ◽  
Theoretical Analysis ◽  
Complex Structure ◽  
Recent Analysis ◽  
Velocity Analysis ◽  
Curvilinear Coordinate System ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Curvilinear Coordinate ◽  
Image Volume

Recent analysis and synthetic examples have shown that many prestack depth migration methods produce nonflat image gathers containing spurious events, even when provided with a kinematically correct migration velocity field, if this velocity field is highly refractive. This pathology occurs in all migration methods that produce partial images as independent migrations of data bins. Shot-geophone prestack depth migration is an exception to this pattern: each point in the prestack image volume depends explicitly on all traces within the migration aperture. Using a ray-theoretical analysis, we have found that shot-geophone migration produces focused (subsurface-offset domain) or flat (scattering-angle domain) image gathers, provided there is a curvilinear coordinate system defining pseudodepth with respect to which the rays carrying significant energy do not turn, and that the acquisition coverage is sufficient to determine all such rays. Although the analysis is theoretical and idealized, a synthetic example suggests that its implications remain valid for practical implementations, and that shot-geophone prestack depth migration could be a particularly appropriate tool for velocity analysis in a complex structure.

Prestack depth migration of an Alberta Foothills data set—The Husky experience

Geophysics ◽  
1998 ◽  
Vol 63 (2) ◽  
pp. 392-398 ◽  
Author(s):  
W.-J. Wu ◽  
L. Lines ◽  
A. Burton ◽  
H.-X. Lu ◽  
J. Zhu ◽  
...  
Keyword(s):  
Velocity Analysis ◽  
Reverse Time ◽  
Prestack Depth Migration ◽  
Data Set ◽  
Depth Migration ◽  
Geological Interpretation ◽  
Prestack Migration ◽  
Velocity Models ◽  
Depth Images ◽  
Migration Velocity Analysis

We produce depth images for an Alberta Foothills line by iteratively using a number of migration and velocity analysis techniques. In imaging steeply dipping layers of a foothills data set, it is apparent that thrust belt geology can violate the conventional assumptions of elevation datum corrections and common midpoint (CMP) stacking. To circumvent these problems, we use migration from topography in which we perform prestack depth migration on the data using correct source and receiver elevations. Migration from topography produces enhanced images of steep shallow reflectors when compared to conventional processing. In addition to migration from topography, we couple prestack depth migration with the continuous adjustment of velocity depth models. A number of criteria are used in doing this. These criteria require that our velocity estimates produce a focused image and that migrated depths in common image gathers be independent of source‐receiver offset. Velocity models are estimated by a series of iterative and interpretive steps involving prestack migration velocity analysis and structural interpretation. Overlays of velocity models on depth migrations should generally show consistency between velocity boundaries and reflection depths. Our preferred seismic depth section has been produced by using prestack reverse‐time depth migration coupled with careful geological interpretation.

Influence of structural dip angles on interval velocity analysis

Geophysics ◽  
2008 ◽  
Vol 73 (4) ◽  
pp. U13-U18 ◽  
Author(s):  
Moshe Reshef ◽  
Andreas Rüger
Keyword(s):  
Velocity Analysis ◽  
Prestack Depth Migration ◽  
Scattering Angle ◽  
Depth Migration ◽  
Interval Velocity ◽  
Important Input ◽  
The Common ◽  
Summation Process

Common scattering-angle and traditional common-offset gathers can be of limited use for interval velocity analysis in regions with complex geologic structures. In the summation process, which occurs when generating each trace in the common-image gather, vital information about structural dip is lost during prestack depth migration. This inadvertently lost data can provide important input to moveout-based velocity-updating algorithms. Maintaining this crucial dip information can improve the quality of the velocity analysis and imaging processes.

Seismic imaging and velocity analysis for an Alberta Foothills seismic survey

Geophysics ◽  
2001 ◽  
Vol 66 (3) ◽  
pp. 721-732 ◽  
Author(s):  
Lanlan Yan ◽  
Larry R. Lines
Keyword(s):  
Seismic Imaging ◽  
Migration Velocity ◽  
Surface Velocity ◽  
Seismic Survey ◽  
Velocity Analysis ◽  
Prestack Depth Migration ◽  
Near Surface ◽  
Depth Migration ◽  
Migration Velocity Analysis ◽  
Imaging Results

Seismic imaging of complex structures from the western Canadian Foothills can be achieved by applying the closely coupled processes of velocity analysis and depth migration. For the purposes of defining these structures in the Shaw Basing area of western Alberta, we performed a series of tests on both synthetic and real data to find optimum imaging procedures for handling large topographic relief, near‐surface velocity variations, and the complex structural geology of steeply dipping formations. To better understand the seismic processing problems, we constructed a typical foothills geological model that included thrust faults and duplex structures, computed the model responses, and then compared the performance of different migration algorithms, including the explicit finite difference (f-x) and Kirchhoff integral methods. When the correct velocity was used in the migration tests, the f-x method was the most effective in migration from topography. In cases where the velocity model was not assumed known, we determined a macrovelocity model by performing migration/velocity analysis by using smiles and frowns in common image gathers and by using depth‐focusing analysis. In applying depth imaging to the seismic survey from the Shaw Basing area, we found that imaging problems were caused partly by near‐surface velocity problems, which were not anticipated in the modeling study. Several comparisons of different migration approaches for these data indicated that prestack depth migration from topography provided the best imaging results when near‐surface velocity information was incorporated. Through iterative and interpretive migration/velocity analysis, we built a macrovelocity model for the final prestack depth migration.

Directional depth migration

Geophysics ◽  
1985 ◽  
Vol 50 (11) ◽  
pp. 1784-1789 ◽  
Author(s):  
J. H. Higginbotham ◽  
Y. Shin ◽  
D. V. Sukup
Keyword(s):  
Velocity Field ◽  
Oil And Gas ◽  
Velocity Fields ◽  
Velocity Analysis ◽  
Depth Migration ◽  
Salt Domes ◽  
Reflection Seismic ◽  
Accurate Knowledge

Complicated geologic structures such as folds, overthrusts, and salt domes can produce reflectors with dips as great as 90 degrees. Because oil and gas accumulations are often associated with these steeply dipping interfaces, accurate processing of reflection seismic information from such areas becomes an important though challenging task. The proper imaging of steeply dipping reflectors requires accurate knowledge of the velocity field through which the wavefronts propagate. Thus, velocity analysis becomes extremely important. In addition to this problem, most migration algorithms have serious difficulties when dip is greater than about 50 degrees. In this discussion, we assume the velocity field is known, the data may be stacked correctly before migration, and the chief concern is migration accuracy. We describe a method for depth migration of very steeply inclined wavefronts through inhomogeneous velocity fields. The extension of the proposed technique to migration before stack is obvious.

Multiwave velocity analysis based on Gaussian beam prestack depth migration

2014 ◽  
Vol 11 (2) ◽  
pp. 186-196 ◽  
Author(s):  
Jian-Guang Han ◽  
Yun Wang ◽  
Ning Han ◽  
Zhan-Tao Xing ◽  
Jun Lu
Keyword(s):  
Gaussian Beam ◽  
Velocity Analysis ◽  
Prestack Depth Migration ◽  
Depth Migration

scholarly journals Imaging complex structure in shallow seismic-reflection data using prestack depth migration

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. B175-B181 ◽  
Author(s):  
John H. Bradford ◽  
Lee M. Liberty ◽  
Mitch W. Lyle ◽  
William P. Clement ◽  
Scott Hess
Keyword(s):  
Seismic Reflection ◽  
Complex Structure ◽  
Volcanic Rocks ◽  
Depth Range ◽  
Prestack Depth Migration ◽  
Measured Velocity ◽  
Seismic Reflection Data ◽  
Depth Migration ◽  
Time Migration ◽  
Shallow Seismic

Prestack depth migration (PSDM) analysis has the potential to significantly improve the accuracy of both shallow seismic reflection images and the measured velocity distributions. In a study designed to image faults in the Alvord Basin, Oregon, at depths from [Formula: see text], PSDM produced a detailed reflection image over the full target depth range. In contrast, poststack time migration produced significant migration artifacts in the upper [Formula: see text] that obscured reflection events and limited the structural interpretation in the shallow section. Additionally, an abrupt increase from [Formula: see text] to [Formula: see text] in the PSDM velocity model constrained the interpretation of the transition from sedimentary basin fill to basement volcanic rocks. PSDM analysis revealed a complex extensional history with at least two distinct phases of basin growth and a midbasin basement high that forms the division between two major basin compartments.

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