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Digital Signal Analysis in Seismic Data Processing
Enders A. Robinson and Osman M. Hassan
New SEG short course
Duration: Two days
This course is designed at an introductory level to cover in some details the theoretical background and the practical applications of digital signal analysis in geophysics. The course describes the basic definitions of digital filters, their coefficients, and their manipulations in time and in frequency domains. The sampling theory and the wavelet concept are introduced. The design and the applications of least-squares filters are covered. Applications of different types of deconvolution filters such as spiking and predictive are discussed along with examples and exercises.
The intended audience for this course are seismic data analysts, field and office processors and seismic interpreters who are seeking to understand some basic and important concepts of digital signal analysis in seismic data processing.
Course Outline
- Introduction
Overview of the reflection seismic method
- Causal digital
Digital filtering of signals; filter coefficients, Z-transform, MA and FIR filters
- Freqency spectra
The Fourier transform; Euler's equation; amplitude and phase characteristics of digital filters; minimum-phase spectrum of a digital filter; dual sensor system
- Sampling
Sampling and Nyquist frequency; sampling geophysical data
- Frequency analysis
Frequency spectrum; magnitude and phase spectra; workshop exercises
- Minimum-delay and feedback
Time series, wavelets, and linear systems; minimum, mixed, and maximum delay; feedback stability and minimum delay
- Least squares filtering
Basic concepts, mathematical details, and examples; multiple reflections, dual sensor system
- Predictive Deconvolution
Weiner prediction and filtering; the prediction error filter; The convolutional model and spiking deconvolution; gap deconvolution, the tail shaping filter and the head shaping filter; examples of predictive deconvolution
- Applications of predictive decon
The general convolutional model, signature deconvolution, predictive deconvolution, prewhitening, prediction distance, convolutional model in the frequency domain and time variant spectral whitening; workshop exercises
- Invese Q-filtering
- Spherical spreading and attenuation; absorption
Instructor Biographies:
Enders A. Robinson
Osman M. Hassan
Seismic Anisotropy: Basic Theory and Applications in Exploration and Reservoir Characterization
Ilya Tsvankin and Vladimir Grechka
Duration: two days
New SEG Short Course
Elastic anisotropy, widely recognized as a typical feature of sedimentary formations, can have a strong influence on seismic data. For example, the difference between the stacking and vertical velocity in anisotropic media is the most common reason for mis-ties in time-to-depth conversion. This course provides the necessary background information about anisotropic wave propagation and discusses modeling, inversion and processing of seismic reflection data in the presence of anisotropy.
The most critical step in extending seismic processing to anisotropic media is to identify and obtain from the data the medium parameters responsible for measured reflection signatures. The main emphasis of the course is on parameter estimation and imaging for vertical transverse isotropy (VTI media) - the anisotropic model usually associated with shales. A description of practical methods of P-wave time processing for VTI media is followed by analysis of the joint inversion of P- and converted PS-waves that can yield the true vertical velocity needed for anisotropic depth migration. Field-data examples illustrate the improvements in imaging achieved by the anisotropic DMO and migration algorithms and the possibility of using the anisotropic coefficients in lithology discrimination. The part devoted to anisotropic AVO analysis includes simple analytic approximations for both the reflection coefficients and amplitude distortions in the anisotropic overburden. The course also introduces fracture-detection methods based on the azimuthal variation of reflection moveout and prestack amplitudes of P- and PS-waves.
The course should be useful for both graduate students and more experienced geophysicists working in exploration or development. Mathematical details are kept to a minimum, but some familiarity with the basics of elastic wave propagation and seismic data processing would be helpful.
Course Outline
- Basic theory of anisotropic wave propagation
- Anisotropic ray tracing
- Notation and seismic signatures for vertical transverse isotropy
- Reflection moveout for vertical transverse isotropy
- Dip moveout in VTI media
- P-wave time-domain signatures in VTI media
- Time-domain velocity analysis in VTI media
- Inversion of nonhyperbolic moveout with field-data examples
- P-wave processing in VTI media
- Moveout of mode-converted (PS) waves and its inversion for VTI media
- Point-source radiation in anisotropic media
- Reflection coefficients in anisotropic media
- AVO analysis in VTI media
- Azimuthal velocity analysis
- Azimuthal moveout inversion for HTI and orthorhombic media
- Azimuthal AVO analysis
- Fracture characterization for a single crack system (HTI media)
- Fracture characterization for multiple fracture sets and anisotropic background
Instructor Biographies:
Ilya Tsvankin
Vladimir Grechka
Migration without the Math — OK maybe a little Greek math
J. Bee Bednar
New SEG short course
Duration: two days
Abstract
This course focuses on the following five issues:
- Available migration algorithms, what they do, how they do it, and why one is better than another.
- Acquisition geometry and its effect on the type and quality of result that can be achieved as processing parameters are tailored to achieve optimum images.
- Migration velocity analysis, what it is, how it works, and why one methodology is superior.
- Migration algorithm sensitivity to velocity.
- Anisotropic velocity analysis and anisotropic migration.
Each of these items is discussed in a practical, data-focused manner. Conclusions are supported through examples using carefully crafted synthetic or real seismic data. Geometrical descriptions and explanations are given preference to precise mathematical analyses,. In all cases, case studies are used in place of complex and cryptic mathematical analysis.
The pros and cons of migration algorithms are evaluated. Deficiencies are illustrated through examples and rigorous understanding of why limitations are present.
Acquisition geometry is shown to have a profound effect on precisely what can be achieved and which results are possible. The effect of surface parameter limitations is clarified and explained. The proper use of specific algorithms in both land and marine environments is made plain
Emerging and concurrent velocity analysis techniques are explained, compared, and quantified. The computation of angle gathers is discussed and their contextual utilization detailed. Automatic velocity analysis, percentage based migration velocity analysis, and tomography are discussed in considerable detail. Simplified synthetic examples demonstrate the decreased sensitivity of advanced wave equation techniques to velocity errors.
Finally, anisotropy and its impact on well ties is explained, detailed and quantified. Techniques for estimating and utilizing anisotropic algorithms are provided and evaluated.
Course Outline
- Part 1 focuses primarily on algorithmic issues.
- Part 2 tackles the necessary pros and cons of migration velocity analysis, including traditional common-image gathers and more modern angle gathers.
- Part 3 provides a live demonstration of how these algorithms work and how processing takes place in mini-cluster environment.
- Part 4 returns to specific data examples that are focused on the fundamental interpretative issues associated with depth imaging. Such issues include lateral placement, well-ties, image quality, and utilization of depth images in a work-flow style strategy to achieve better and better interpretations.
Instructor Biography:
J. Bee Bednar
Understanding Seismic Anisotropy in Exploration and Exploitation
Leon Thomsen
Duration: one day
Course Description
All rock masses are seismically anisotropic, but we generally ignore this in our seismic acquisition, processing, and interpretation. The anisotropy nonetheless does affect our data, in ways that limit the effectiveness with which we can use it, so long as we ignore it. In this short course, we will understand why this inconsistency between reality and practice has been so successful in the past, and why it will be less successful in the future, as we acquire better seismic data (especially including vector seismic data), and correspondingly higher expectations of it. We will further understand how we can modify our practice so as to more fully realize the potential inherent in our data, through algorithms, which recognize the fact of seismic anisotropy.
Who should attend?
This is an excellent opportunity for all geophysicists to learn how a fundamental property of rocks impacts all our data and how to deal with it.
Instructor Biography:
Leon Thomsen
Paul Weimer
Overview
This course provides geophysicists with a broad overview of the petroleum systems of deep-water settings. The course design allows geophysicists to quickly integrate the information into their daily workflow. The material presented is approximately the 80-85th percentile of available information. Lectures will be complemented by extensive references to key publications that geophysicists may use to follow up. This course emphasizes the geologic aspects of deep-water deposits.
Summary
The course will start with an overview of the geology of deep-water systems, past, present and future. This review will cover the recent trends in deep-water in terms of drilling results, and introduce the elements of petroleum systems—reservoirs, traps, seals, source rock, migration, and timing.
The key characteristics of the key reservoir elements in turbidite systems are: a) sheet sands (layered and amalgamated), b) channel fill, c) thin beds (overbank), and (d) slides and debris flows. The seismic stratigraphic expression of these systems is present in 2D, shallow 3D, and depth 3D, and integrated with the wireline log expression and information from outcrops, cores, and biostratigraphy. Examples from several producing basins around the world illustrate these points. The production history and the reservoir challenges in developing each of these fields is discussed.
Participants are introduced to the basic occurrences of turbidite systems in a sequence stratigraphic framework. Examples show how to modify the basic model for each kind of basin setting (structural setting, faults, and salt), high frequency sequences, sediment delivery systems, and the effects of grain sizes on turbidite systems. Carbonate and lacustrine systems are also discussed.
Many different kinds of basins produce from turbidite systems. A review of these basins shows the different tectonic settings and associated structural styles. The review also demonstrates that most reservoirs are pure stratigraphic traps or combined traps. A review of seals, source rocks and modeling principles gives the geophysicist practical techniques for understanding deep-water systems.
The course concludes with a summary of what is important in the exploration for and development of deep-water systems. The application of these techniques to each geophysicist’s current projects is key, as is the difference between frontier exploration and exploration in mature basins with deeper potential. Examples from 3 or 4 basins distributed globally illustrate the principles. These examples will also demonstrate that there is deep-water potential in most basins globally.
Instructor Biography:
Paul Weimer
Seismic Stratigraphy and Seismic Geomorphology into the 21st Century
Henry Posamentier
Duration: two days
Who should attend
Geologists and geophysicists, both in industry and academia. Materials covered will be valuable to both explorationists and exploitationists.
Objectives
This course is designed to enhance interpretation skill sets with regard to geologic interpretation of seismic data. The overall objective is to present methods for reducing risk with regard to prediction of lithology, reservoir compartmentalization, and stratigraphic trapping potential in exploration and production.
Specifically, the participant will be shown:
- workflows designed to facilitate extraction of stratigraphic insights from 3D seismic data
- techniques for 3D seismic geomorphologic/stratigraphic analyses
- numerous examples of various depositional systems in various depositional settings
The application of seismic geomorphology and seismic stratigraphy to exploration and field development is a natural consequence of the advent of high-quality and increasingly more affordable and widespread 3D seismic data currently available. Integrating analyses of plan view (geomorphologic) and section view (stratigraphic) images can significantly enhance predictions of the spatial and temporal distribution of subsurface lithology (reservoir, source, and seal), compartmentalization, and stratigraphic trapping capabilities, as well as enhanced understanding of process sedimentology and sequence stratigraphy.
Participants in the course will be exposed to seismic geomorphologic/stratigraphic workflows, which involve 1) initial reconnaissance through 3D volumes using various slicing techniques using a variety of different seismic attribute volumes including full stack reflection amplitudes, near and far stacked amplitude volumes, and coherence volumes, as well as opacity rendering, 2) focus on features of geologic interest and further investigate through a combination of detailed slicing, interval attributes, horizon picking and amplitude extraction, horizon illumination, etc., and 3) comprehensive integration of seismic geomorphologic analyses with seismic stratigraphic analyses, whereby the plan view is integrated with the section view to ensure a consistent interpretation.
Course lectures will involve both PowerPoint presentations as well as interactive interpretation of 3D seismic data. A wide variety of depositional settings will be shown, ranging from non-marine to marginal marine, shelf and deep water, and will include both clastic as well as carbonate depositional environments. Concepts as well as applications pertaining to seismic-based analyses of depositional systems will be covered in detail.
Instructor Biography:
Henry Posamentier
Magnetotellurics for Natural Resources: From Acquisition through Interpretation
Karen Christopherson
Duration: two days
New SEG Short Course
In the last ten years the use of magnetotelluric and audio-magnetotelluric methods for resource exploration and exploitation has increased significantly and there is a need for the geophysicist to better understand the theory, application and interpretation of magnetotelluric (MT) and Audio-MT methods. This course will provide the interested geophysicist with the knowledge and skills necessary to design and manage cost-effective MT field programs and to understand the data processing and interpretation issues. Over the two days of the course the following topics will be investigated: theory, applications and acquisition, processing and interpretation of data. Equipment will be shown on site and MT interpretation software demonstrations will be given. Attendees will be polled prior to the course as to what their interests are, and curriculum revised accordingly. The course can be structured to mineral, petroleum, and/or groundwater exploration. Emphasis can be shifted from the more theoretical to practical (including case histories, guest lectures, and computer hands-on software trials) as attendees prefer.
Course Outline
- Theory
- Maxwell's Equations and fundamental physics of technique
- Source fields
- History
- Applications
- Where it can/cannot be used
- Limitations -- cultural noise
- Targets
- Resolution
- Acquisition/ Equipment
- Equipment manufacturers
- Types of arrays
- Logistics
- Manufacturer reps -- hands-on demos, view of equipment
- Processing
- Standard parameters
- Noise reduction/filtering
- Routine processing
- 'Robust' processing
- Interpretation
- 1D -- Forward and inverse, limitations
- 2D -- Forward and inverse, limitations and caveats
- 3D -- Current codes, benefits, demonstration and case histories
- Workstations -- WinGLink, Geotools, others
- Output -- Cross-sections and maps
Instructor Biography:
Karen Christopherson
The Magnetic Method in Mineral Exploration: Geomagnetism to Interpretation
Shanti Rajagopalan
Duration: two to three days
This course is intended for geologists and geophysicists who aim to interpret geology and explore for minerals using magnetic data.
The magnetic method is the most commonly used method in mineral exploration and applied over the whole scale from region selection to target identification. The course covers geomagnetism, rock magnetism, surveys, magnetic anomalies and interpretation. The course is focused on the interpretation of aeromagnetic maps in geological terms. An important section covers the inter-relationship between rock magnetism, geological history, magnetic anomalies and ore deposits. Complex ideas are proved by example rather than merely by equations. The quantitative and geological interpretation of magnetic surveys will include data from synthetic surveys, different geological terranes and one or more selected areas from the participants' own project areas. Course participants will examine how GIS can be used to present and improve geophysical interpretation.
The course is intended to be presented in two or three days according to demand.
Course Outline
- Review of Geomagnetism including the IGRF
- Rock magnetism
Bulk magnetization, magnetic mineral petrogenesis, remanent magnetization - The nature of magnetic anomalies
Effect of source parameters, magnetic latitude, remanence and topography on anomaly shape - Anomaly transformation Continuation, gradients, analytic signal, etc.
- Display formats
Stacked profiles, contours, images, image enhancement - Quantitative Interpretation using graphical techniques and forward modeling software
- Geological Interpretation
Mapping lithomagnetic units and interpreting structure
- Computer modeling to study effect of source geometry, magnetic latitude, and remanence on anomaly shape
- Computer modeling to understand effect of different filters
- Workshop on interpretation of structure and mapping of lithomagnetic units from example geological maps from different terranes and participants own project areas if available.
Michal Ruder
Duration: two days
This course is designed for geologists and geophysicists with interests in potential fields and regional tectonics. Presented as a two-day seminar, we concentrate on fundamentals for the first day and tackle advanced topics during the second day. Attendees with little previous experience in gravity and magnetics will find the pace comfortable and the concepts quite accessible. Attendees who have already worked with potential field data will find the first day to be a helpful review of basic concepts and the second day to be quite challenging and thought-provoking.
Course Outline
- Fundamentals of potential theory
- Application of the theory to geology of the Earth's crust
- Acquisition techniques and parameters for gravity and magnetic surveys
- Conventional and innovative two-dimensional filtering techniques used to enhance potential field data
- Magnetic depth estimation techniques
- Gravity and magnetic gradiometry
- Airborne gravity methods
Instructor Biography:
Michal Ruder
