[PDF] Prestack Depth Migration And Velocity Model Building eBook

Author : Ian Frederick Jones
Publisher : SEG Books
Page : 1427 pages
File Size : 34,17 MB
Release : 2008
Category : Science
ISBN : 1560801476

GET BOOK

Compilation of material published 1983-2004.

Author : Phil Schultz
Publisher : SEG Books
Page : 234 pages
File Size : 35,40 MB
Release : 1998-12-30
Category : Science
ISBN : 1560800917

GET BOOK

A 3D velocity model is built with a both geophysical and geologic input because of the accuracy demands of depth imaging, so it becomes an increasingly effective interpretive tool. This book addresses ways in which the interpreter should participate in development of the model and underscores its interpretive value with case study examples.

Author : Stuart Fagin
Publisher : SEG Books
Page : 184 pages
File Size : 23,33 MB
Release : 1998
Category : Seismic prospecting
ISBN : 1560800852

GET BOOK

This is an informal review of the principle techniques and issues associated with prestack depth imaging. The intended audience for this book would be those seismic interpreters, processors, managers, and explorationists who require basic familiarity with the technology that has so greatly expanded the range of geologic structures that can be successfully imaged. The emphasis of the book is on velocity-model building techniques that are the key to successful depth imaging.

Author :
Publisher :
Page : 4 pages
File Size : 38,32 MB
Release : 1997
Category :
ISBN :

GET BOOK

Finite-difference, prestack, depth migrations offers significant improvements over Kirchhoff methods in imaging near or under salt structures. The authors have implemented a finite-difference prestack depth migration algorithm for use on massively parallel computers which is discussed. The image quality of the finite-difference scheme has been investigated and suggested improvements are discussed. In this presentation, the authors discuss an implicit finite difference migration code, called Salvo, that has been developed through an ACTI (Advanced Computational Technology Initiative) joint project. This code is designed to be efficient on a variety of massively parallel computers. It takes advantage of both frequency and spatial parallelism as well as the use of nodes dedicated to data input/output (I/O). Besides giving an overview of the finite-difference algorithm and some of the parallelism techniques used, migration results using both Kirchhoff and finite-difference migration will be presented and compared. The authors start out with a very simple Cartoon model where one can intuitively see the multiple travel paths and some of the potential problems that will be encountered with Kirchhoff migration. More complex synthetic models as well as results from actual seismic data from the Gulf of Mexico will be shown.

Author : Taylor Jerome Dahlke
Publisher :
Page : pages
File Size : 32,57 MB
Release : 2019
Category :
ISBN :

GET BOOK

As oil and gas extraction becomes more advanced, exploration becomes increasingly focused on imaging near or under complex salt geology, which necessitates detailed velocity models with sharp interfaces. Current state-of-the-art practices include the use of Full-Waveform Inversion (FWI). However, this type of approach can result in salt body models that lack the sharp interfaces characteristic of this type of geobody. This is typically due to the computational expense of using increasingly high frequencies in the data. These interfaces can be elegantly tracked as sharp boundaries using the level sets of an implicit surface. Used in conjunction with shape optimization, one can invert for salt boundaries that fit recorded data in a FWI style objective function that is parameterized in terms of both the implicit surface and a background velocity model. While this addition of the implicit surface requires more model parameters, radial basis functions can be used to create a sparse parameterization of it, which can hasten convergence of the inversion. The implicit surface also allows for embedding information about the certainty of different salt boundary regions by means of its initialization. This information allows for intelligent guidance of the inversion based on interpreter input, which can help the inversion avoid local minima. The result of testing this inversion workflow on a 3D Gulf of Mexico dataset shows that it can be a useful tool for refining salt models, as the seismic images produced from the final model shows clearer and more consistent features below the updated salt area.

Author : Yaxun Tang
Publisher : Stanford University
Page : 239 pages
File Size : 35,90 MB
Release : 2011
Category :
ISBN :

GET BOOK

This thesis develops a novel target-oriented inversion framework that uses wavefields as carriers of information to image both low-wavenumber component (a.k.a. background velocity) and high-wavenumber component (a.k.a. reflectivity) of the earth model in complex geological settings, such as subsalt regions. I address the problem of reflectivity imaging with target-oriented wavefield least-squares migration, and the problem of velocity estimation with target-oriented wavefield tomography. Reflectivity images of the subsurface are commonly produced by prestack depth migration. When the overburden is complex and the reflectors are unevenly or insufficiently illuminated, the migration operator alone is inadequate to provide an optimal image. I tackle the problem of distorted illumination in reflectivity imaging by wavefield least-squares migration. I formulate least-squares migration in the image domain and solve it in a target-oriented fashion. In the image-domain formulation, explicit computation of the Hessian operator (the resolution function that measures the illumination deficiency of the imaging system) is the most important and challenging step. I develop a novel method based on phase encoding to efficiently and accurately compute the target-oriented Hessian operator. The Hessian operator is then used to recover the reflectivity by iterative inverse filtering. I regularize the inversion with dip constraints, which naturally incorporate interpreted geological information into the inversion. Accurate imaging of the reflectivity also requires an accurate background velocity model. High-quality velocity model-building in complex geology requires wavefield-based velocity analysis to properly model band-limited wave phenomena. However, the high cost and lack of flexibility of target-oriented model-building prevent this method from being widely used in practice. I overcome the cost and flexibility issues of wavefield-based migration velocity analysis by developing target-oriented wavefield tomography. Target-oriented wavefield tomography is achieved by synthesizing a new data set specifically for velocity analysis. The new data set is generated based on an initial unfocused target image and by a novel application of generalized Born wavefield modeling, which correctly preserves velocity kinematics by modeling both zero and non-zero subsurface-offset-domain images. The new data set can be synthesized for a chosen target region with velocity inaccuracies. The reduced data size and computation domain, therefore, greatly improve the efficiency and flexibility of wavefield tomography, allowing fast and interpretation-driven interactive wavefield-based velocity analysis, where different geological scenarios or hypotheses can be tested in quasi-real time. The proposed target-oriented inversion framework successfully estimates subsalt velocities and recovers subsalt reflectivities from distorted illumination from 2-D synthetic and 3-D field data.

Author : Stuart William Fagin
Publisher :
Page : 173 pages
File Size : 42,30 MB
Release : 1998
Category : Seismic prospecting
ISBN : 9781560802013

GET BOOK

This is an informal review of the principle techniques and issues associated with prestack depth imaging. The intended audience for this book would be those seismic interpreters, processors, managers, and explorationists who require basic familiarity with the technology that has so greatly expanded the range of geologic structures that can be successfully imaged. The emphasis of the book is on velocity-model building techniques that are the key to successful depth imaging.