Estimating and interpreting velocity uncertainty in migrated images and AVO attributes

Geophysics ◽  
2001 ◽  
Vol 66 (4) ◽  
pp. 1208-1216 ◽  
Author(s):  
H. Grubb ◽  
A. Tura ◽  
C. Hanitzsch
Keyword(s):  
Velocity Field ◽  
Velocity Fields ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Avo Inversion ◽  
Point Of Interest ◽  
Amplitude Versus Offset ◽  
Attribute Analysis ◽  
Complex Structural ◽  
Avo Attributes

Estimating a suitable velocity field for use in prestack depth migration is inherently uncertain because of limitations on the available data and estimation techniques. This uncertainty affects both the migrated depth of structures and their amplitudes in the inverted images. These effects can be estimated by performing multiple migrations with a set of velocity fields and colocating features in the migrated images. This lets us examine the imaging procedure’s sensitivity to changes in the velocity field so we can assess both structural and amplitude uncertainties in migrated images. These two types of uncertainties affect interpretation in different ways. For instance, with structural uncertainty interpretation we consider the change in migrated location of structures when deciding on drilling locations, optimizing well trajectories, or computing uncertainty in volumetric calculations. With amplitude uncertainty or amplitude versus offset (AVO) uncertainty interpretation, we consider (1) uncertainty in crossplots of pairs of AVO attributes at a point of interest or (2) uncertainty of the attribute values along identified structures. For any interpretation informing a decision, the uncertainty can help estimate risk. Our data processing approach is based on amplitude‐preserving prestack depth migration followed by AVO inversion, or AVO migration/inversion. It is valid for estimating AVO attributes in simple to moderately complex structural settings. Our methods of assessing the effect of velocity uncertainty can also be applied when obtaining structural uncertainties for a complex overburden geology or amplitude uncertainties in conventional NMO‐based AVO analysis. They may also be applied straightforwardly to any poststack attribute analysis. Key to the approach is the availability of multiple velocity fields to generate multiple migrated images. In our application, an automatic algorithm samples possible fields, but the set of fields to consider could be generated from another source, such as interpretation.

scholarly journals Analisis AVO untuk Mengetahui Penyebaran Hidrokarbon Berdasarkan Faktor Fluida (Studi Kasus Lapangan “H” Formasi Talang Akar Cekungan Jawa Barat Utara)

2016 ◽  
Vol 3 (02) ◽  
pp. 209
Author(s):  
Muhammad Nur Handoyo ◽  
Agus Setyawan ◽  
Mualimin Muhammad
Keyword(s):  
Seismic Data ◽  
Class Iii ◽  
Avo Inversion ◽  
Amplitude Versus Offset ◽  
Attribute Analysis ◽  
Fluid Factor ◽  
Inversion Analysis ◽  
Amplitude Versus

<span>Amplitude versus offset (AVO) inversion analysis can be used to determine the spread of <span>hydrocarbons on seismic data. In this study we conducted AVO on reservoir layer Talang <span>Akar’s formation (TAF). AVO inversion results are angle stack, normal incident reflectivity <span>(intercept), gradient and fluid factor. Angle stack attribute analysis showed an AVO anomaly <span>in the reservoir TAF layer, amplitude has increased negative value from near angle stack to far <span>angle stack. The result of crossplot normal incident reflectivity (intercept) with gradient <span>indicates reservoir TAF layer including Class III AVO anomaly. While the analysis of fluid <span>factor attribute has a negative value thus reservoir TAF layer indicates a potential <span>hydrocarbon.</span></span></span></span></span></span></span></span><br /></span>

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.

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.

Forward modeling attribute analysis for AVO and prestack depth migration

2002 ◽  
Author(s):  
Toshi Chang ◽  
Chih‐Wen Kue ◽  
Luis Canales ◽  
Chung‐Chi Shih
Keyword(s):  
Forward Modeling ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Attribute Analysis

3-D preserved amplitude prestack depth migration on a workstation

Geophysics ◽  
1999 ◽  
Vol 64 (1) ◽  
pp. 222-229 ◽  
Author(s):  
Philippe Thierry ◽  
Gilles Lambaré ◽  
Pascal Podvin ◽  
Mark S. Noble
Keyword(s):  
Seismic Reflection ◽  
Velocity Fields ◽  
Prestack Depth Migration ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Depth Migration ◽  
Cpu Time ◽  
Reflection Data ◽  
Marine Data ◽  
Single Processor

We present an algorithm based on the ray+Born approximation for 3-D preserved amplitude prestack depth migration (PAPsDM) of seismic reflection data. This ray+Born inversion scheme allows the quantitative recovery of model perturbations. The Green’s functions are estimated by dynamic ray tracing in 3-D heterogeneous smooth velocity fields with a wavefront construction (WFC) method. The PAPsDM algorithm was implemented on a single‐processor Sun Sparc 20 workstation. Special attention was paid to CPU efficiency and memory requirements. We present an application on a 3-D real marine data set (13 Gbytes). About one week of CPU time is needed to obtain a migrated image of 7 × 1 × 1 km.

scholarly journals Experimental Validation of Falling Liquid Film Models: Velocity Assumption and Velocity Field Comparison

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1205
Author(s):  
Ruiqi Wang ◽  
Riqiang Duan ◽  
Haijun Jia
Keyword(s):  
Experimental Data ◽  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Experimental Validation ◽  
Particle Image ◽  
Velocity Fields ◽  
Number Range ◽  
Comparison Results ◽  
Image Velocimetry ◽  
Experimental Particle

This publication focuses on the experimental validation of film models by comparing constructed and experimental velocity fields based on model and elementary experimental data. The film experiment covers Kapitza numbers Ka = 278.8 and Ka = 4538.6, a Reynolds number range of 1.6–52, and disturbance frequencies of 0, 2, 5, and 7 Hz. Compared to previous publications, the applied methodology has boundary identification procedures that are more refined and provide additional adaptive particle image velocimetry (PIV) method access to synthetic particle images. The experimental method was validated with a comparison with experimental particle image velocimetry and planar laser induced fluorescence (PIV/PLIF) results, Nusselt’s theoretical prediction, and experimental particle tracking velocimetry (PTV) results of flat steady cases, and a good continuity equation reproduction of transient cases proves the method’s fidelity. The velocity fields are reconstructed based on different film flow model velocity profile assumptions such as experimental film thickness, flow rates, and their derivatives, providing a validation method of film model by comparison between reconstructed velocity experimental data and experimental velocity data. The comparison results show that the first-order weighted residual model (WRM) and regularized model (RM) are very similar, although they may fail to predict the velocity field in rapidly changing zones such as the front of the main hump and the first capillary wave troughs.

Kinematic interpretation in the prestack depth‐migrated domain

Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1226-1237 ◽  
Author(s):  
Irina Apostoiu‐Marin ◽  
Andreas Ehinger
Keyword(s):  
Signal To Noise Ratio ◽  
Velocity Model ◽  
Point Of View ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Velocity Models ◽  
Time Domain Data ◽  
And Migration ◽  
Point To Point ◽  
Homogeneous Media

Prestack depth migration can be used in the velocity model estimation process if one succeeds in interpreting depth events obtained with erroneous velocity models. The interpretational difficulty arises from the fact that migration with erroneous velocity does not yield the geologically correct reflector geometries and that individual migrated images suffer from poor signal‐to‐noise ratio. Moreover, migrated events may be of considerable complexity and thus hard to identify. In this paper, we examine the influence of wrong velocity models on the output of prestack depth migration in the case of straight reflector and point diffractor data in homogeneous media. To avoid obscuring migration results by artifacts (“smiles”), we use a geometrical technique for modeling and migration yielding a point‐to‐point map from time‐domain data to depth‐domain data. We discover that strong deformation of migrated events may occur even in situations of simple structures and small velocity errors. From a kinematical point of view, we compare the results of common‐shot and common‐offset migration. and we find that common‐offset migration with erroneous velocity models yields less severe image distortion than common‐shot migration. However, for any kind of migration, it is important to use the entire cube of migrated data to consistently interpret in the prestack depth‐migrated domain.

Simulation of a seismic survey with combined surface and in-mine data acquisition for imaging steeply dipping ore veins

2021 ◽  
Author(s):  
Olaf Hellwig ◽  
Stefan Buske
Keyword(s):  
Finite Difference ◽  
Message Passing Interface ◽  
Seismic Survey ◽  
Difference Operators ◽  
Mining District ◽  
Prestack Depth Migration ◽  
Data Set ◽  
Depth Migration ◽  
Difference Grid ◽  
Triangulated Surfaces

&lt;p&gt;The polymetallic, hydrothermal deposit of the Freiberg mining district in the southeastern part of Germany is characterised by ore veins that are framed by Proterozoic orthogneiss. The ore veins consist mainly of quarz, sulfides, carbonates, barite and flourite, which are associated with silver, lead and tin. Today the Freiberg University of Mining and Technology is operating the shafts Reiche Zeche and Alte Elisabeth for research and teaching purposes with altogether 14 km of accessible underground galleries. The mine together with the most prominent geological structures of the central mining district are included in a 3D digital model, which is used in this study to study seismic acquisition geometries that can help to image the shallow as well as the deeper parts of the ore-bearing veins. These veins with dip angles between 40&amp;#176; and 85&amp;#176; are represented by triangulated surfaces in the digital geological model. In order to import these surfaces into our seismic finite-difference simulation code, they have to be converted into bodies with a certain thickness and specific elastic properties in a first step. In a second step, these bodies with their properties have to be discretized on a hexahedral finite-difference grid with dimensions of 1000 m by 1000 m in the horizontal direction and 500 m in the vertical direction. Sources and receiver lines are placed on the surface along roads near the mine. A Ricker wavelet with a central frequency of 50 Hz is used as the source signature at all excitation points. Beside the surface receivers, additional receivers are situated in accessible galleries of the mine at three different depth levels of 100 m, 150 m and 220 m below the surface. Since previous mining activities followed primarily the ore veins, there are only few pilot-headings that cut through longer gneiss sections. Only these positions surrounded by gneiss are suitable for imaging the ore veins. Based on this geometry, a synthetic seismic data set is generated with our explicit finite-difference time-stepping scheme, which solves the acoustic wave equation with second order accurate finite-difference operators in space and time. The scheme is parallelised using a decomposition of the spatial finite-difference grid into subdomains and Message Passing Interface for the exchange of the wavefields between neighbouring subdomains. The resulting synthetic seismic shot gathers are used as input for Kirchhoff prestack depth migration as well as Fresnel volume migration in order to image the ore veins. Only a top mute to remove the direct waves and a time-dependent gain to correct the amplitude decay due to the geometrical spreading are applied to the data before the migration. The combination of surface and in-mine acquisition helps to improve the image of the deeper parts of the dipping ore veins. Considering the limitations for placing receivers in the mine, Fresnel volume migration as a focusing version of Kirchhoff prestack depth migration helps to avoid migration artefacts caused by this sparse and limited acquisition geometry.&lt;/p&gt;

Solutions for Non-Newtonian Flow Into Elliptical Openings

1991 ◽  
Vol 58 (3) ◽  
pp. 820-824 ◽  
Author(s):  
A. Bogobowicz ◽  
L. Rothenburg ◽  
M. B. Dusseault
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Steady State ◽  
Hydrostatic Pressure ◽  
Velocity Field ◽  
Velocity Fields ◽  
Newtonian Flow ◽  
Element Analysis ◽  
Elliptical Opening ◽  
Elliptical Coordinates

A semi-analytical solution for plane velocity fields describing steady-state incompressible flow of nonlinearly viscous fluid into an elliptical opening is presented. The flow is driven by hydrostatic pressure applied at infinity. The solution is obtained by minimizing the rate of energy dissipation on a sufficiently flexible incompressible velocity field in elliptical coordinates. The medium is described by a power creep law and solutions are obtained for a range of exponents and ellipse eccentricites. The obtained solutions compare favorably with results of finite element analysis.

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