From now on I will share my books that I reading. I become a good base knowledge when we become a geophysicist, this books was written by Oz Yilmaz, it tell us about seismic data processing. Here you are.. (enjoy it ^_^)
The seismic method plays a prominent role in the search for hydrocarbons. Seismic exploration consists of three main stages: data acquisition, processing, and interpretation. This book is intended to help the seismic analyst understand the fundamentals of the techniques used in processing seismic data. In particular, emphasis is given to the practical aspects of data analysis.
Topics in this book are treated in two phases. First, each process is described from a physical viewpoint, with less emphasis on mathematical development. In doing so, geometric means are used extensively to help the reader gain the physical insight into the different processes. Second, the geophysical parameters that affect the fidelity of the resulting output from each process are critically examined via an extensive series of synthetic and real data examples. For the student of reflection seismology and new entrants to the seismic industry, this book tries to provide insights into the practical aspects of the application of the theory of time series and waves. For experienced seismic explorationists, this book should serve as a refresher and handy reference. However, it is not just meant for the seismic analyst. Explorationists who would like to gain a practical background in seismic data processing without any mathematical burden also should benefit from it. Nevertheless, for the more theoretically inclined, a mathematical treatise on the main subjects is provided in the appendixes.
The seismic analyst is confronted daily with the important tasks of:
A) selecting a proper sequence of processing steps appropriate for the field data under consideration,
B) selecting an appropriate set of parameters for each processing step, and
C) evaluating the resulting output from each processing step, then diagnosing any problems caused by improper parameter selection.
There is a well-established sequence for standard seismic data processing. The three principal processes deconvolution, stacking, and migration make up the foundation of routine processing. There also are some auxiliary processes that help improve the effectiveness of the principle processes. Questions often arise as to the kind of auxiliary processes that should be used and when they should be applied. For example, if shot records contain an abundance of source-generated coherent noise, then dip filtering may be valuable before deconvolution. Beam steering may be necessary to improve the signal-to-noise ratio while reducing the number of channels in processing by a factor of as much as four. Residual statics corrections often are required for improving velocity estimation and stacking. In a daily production environment, many questions arise concerning the optimal parameter selection for each process. Some of the most repeatedly asked questions are: What is a good length for the deconvolution operator? What should the prediction lag be? What should the design gate for the operator be? How should the correlation window be chosen in residual statics computations? What kind of aperture width should one select in Kirchhoff migration? What is the optimum depth step size in finite-difference migration? Many more questions could be included in this list of questions. To help answer these questions, a large number of examples using both field and synthetic data and describing a wide range of processing parameters are provided.
The first edition, entitled Seismic Data Processing, was published in 1987 by the Society of Exploration Geophysicists. Thereafter, I began to work on the second edition almost immediately. My objective was to capture continuously the new developments that were taking place in the seismic industry. The second edition is the culmination of this continuous update over the past ten years. The updating process was based on exhaustive model- and real-data experiments with the results of the research and development work of my own and many others. I have also drawn an extensive and demonstrative set of real-data examples from the numerous case studies that I onducted during the course of the update. Another source of update was of course the prolific literature on exploration seismology.
This second edition embodies the broad scope of seismic data analysis — processing, inversion, and interpretation of seismic data. I shall give a brief summary of the most important new developments in seismic data analysis during the past 15 years. To begin with, he 3-D seismic method took a centrally dornmant position in the exploration and development of oil and gas fields. Algorithms for 3-D seismic data processing, including 3-D dip-moveout correction, 3-D refraction and residual statics corrections, and 3-D migration have now become an integral part of the applications library of the seismic data processing systems in use today. Additionally, noise attenuation based on prediction filtering is now applied routinely to seismic data. Techniques for multiple attenuation based on the Radon transform and wave extrapolation have been successfully demonstrated on field data.
Shortly after 3-D migration, we also began to image the subsurface before stacking. Efficient workflows for 3-D prestack time migration are in use today not only to image the subsurface more accurately in the presence of conflicting dips with different stacking velocities but also to generate common-reflection-point gathers that can be used to perform prestack amplitude inversion and thus obtain attributes associated with amplitude variations with offset. 3-D prestack time migration also paves the way for estimating a 3-D rms velocity field that can be used to perform Dix conversion and thus obtain a 3-D interval velocity field.
Concurrent with prestack imaging, we began to image the subsurface also in depth to account for strong lateral velocity variations. During the last decade, years of effort in research and development conducted in previous decades have led to practical inversion methods for earth modeling and imaging in depth. Using appropriate inversion methods, we derive a seismic representation of an earth model in depth, described by two sets of parameters layer velocities and reflector geometries, for low-relief, complex, and complex overburden structures. The power of 3-D visualization has given us the ability to create an earth model in depth with the accuracy needed to image in depth, and that within an efficient work schedule. Additionally, the rapid growth in computer power has enabled us to generate an earth image in depth from 3-D prestack depth migration of large data volumes, again within acceptable work schedules.
To get the most out of the image volumes derived from 3-D prestack time and depth migrations, we now make extensive use of 3-D visualization in seismic interpretation. Using a volume-based interpretation strategy, not only do we pick time or depth horizons to delineate the structural model of the subsurface, but we also make use of the seismic amplitudes to infer the depositional model of the subsurface.
The road ahead for exploration seismology includes three main topics 4-D seismic method, 4-C seismic method, and anisotropy, all aimed at seismic characterization of oil and gas reservoirs and eventually monitoring their depletions. By recording 3-D seismic data over the field that is being developed and produced at appropriate time intervals, we may detect changes in the reservoir conditions, such as fluid saturation and pore pressure. Such changes may be related to changes in the seismic amplitudes from one 3-D survey to the next. Time-lapse 3-D seismic monitoring of reservoirs is referred to as the 4-D seismic method. The fourth dimension represents the calendar time over which the reservoir is being monitored. Potential applications of the 4-D seismic method include monitoring the spatial extent of the steam front following in-situ combustion or steam injection used for thermal recovery, monitoring the spatial extent of the injected water front used for secondary recovery, imaging bypassed oil, determining flow properties of sealing or leaking faults, and detecting changes in oil-water contact.
Some reservoirs can be identified and monitored better by using shear-wave data. For instance, acoustic impedance contrast at the top-reservoir boundary may be too small to detect, whereas shear-wave impedance contrast may be sufficiently large to detect. By recording multicomponent data at the ocean bottom, P-wave and S-wave images can be derived. Commonly, four data components are recorded the pressure wave-field and inline, crossline, and vertical components of particle velocity. Thus, the multicomponent seismic data recording and analysis is often referred to as the 4-C seismic method. Potential applications of the 4-C seismic method include imaging beneath gas plumes, salt domes, and basalts, delineating reservoir boundaries with a higher S-wave impedance contrast than P-wave impedance contrast, differentiating sand from shale, detection of fluid phase change from oil-bearing to water-bearing sands, detection of vertical fracture orientation, mapping hydrocarbon saturation, and mapping oil-water contact.
Until recently, exploration seismology at large has been based on the assumption of an isotropic medium, albeit we have been cognizant of anisotropic behavior of reservoir rocks. Seismic anisotropy often is associated with directional variations in velocities. For instance, in a vertically fractured limestone reservoir, velocity in the fracture direction is lower than velocity in the direction perpendicular to the plane of fracturing, giving rise to azimuthal anisotropy. Another directional variation of velocities involves horizontal layering and fracturing of rocks parallel to the layering. In this case, velocity in the horizontal direction is higher than the vertical direction, giving rise to transverse isotropy.
In addition to a continuing effort to improve the existing 3-D time- and depth-domain applications, current research and development in seismic data analysis is focused on time- and depth-domain analysis of 4-D and 4-C seismic data while accounting for anisotropy.
Topics in this book are organized to reflect the increasing degree of complexity in the data analysis and the progress made in exploration seismology. Volume I is devoted to 2-D conventional processing based on the three principle processes deconvolution, stacking, and migration. Volume I is devoted to topics beyond 2-D conventional processing 3-D seismic exploration, seismic inversion for earth modeling and imaging in depth, 4-D seismic method, 4-C seismic method, and anisotropy. Each chapter is accompanied by an appendix that includes a mathematical treatise of selected topics from the chapter itself. As such, practical aspects of seismic data analysis are treated within the chapters themselves without the burden of the theoretical details.
When used as a textbook in a university, I recommend Volume I for a first-semester senior-level course and Volume II for a second-semester senior-level course or a first-year graduate course. Optionally, you may consider an additional one-semester senior- or graduate- level course on the applied theory of exploration seismology based on primarily the appendixes.
If you are a seismic analyst using this book as a reference, you can study the practical aspects of seismic data analysis in relation to the projects you are conducting to get helpful hints on the algorithms and workflows. If you are a research geophysicist using this book as a reference, you can study the practical aspects of a specific application of interest to get helpful hints on what assumptions can be made in relation to that application. Also, you can study the appendixes to initiate yourself into the basic theory on the subject of your interest.
This is the end of Oz Yilmaz Preface on his book seismic data processing volume I, it give us some general information about the book and seismic method.
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