The Principles of Quantitative Acoustical Imaging

 Instructor Prof. Dr Dries Gisolf (Delft Inversion, Netherlands) Duration 2 days Disciplines Geophysics – Surface Imaging Level Advanced Language English EurGeol 10 CPD points Keywords AMPLITUDE   EXTRAPOLATION   FOURIER   INVERSION   MIGRATION   RADON TRANSFORM   REFLECTION   WAVE EQUATION   WAVE PROPAGATION

Course description

This course presents a systematic approach to imaging of acoustic reflection data and the extraction of media property information from the image amplitudes, based on wave theory. Although the approach is valid for a wide range of acoustical frequencies and applications, there is a bias towards seismic imaging.

The theory of acoustic wave propagation is presented, from the constituent equations Hooke and Newton, to the acoustic wave equation, to wavefield extrapolation and eventually to extraction of image amplitudes. This last process is treated as an inversion problem, where downward projected wavefields are directly inverted for the media properties. A feature of the course is the careful analysis of every step in these processes in terms of the linearity of the wavefields in the media property representation they are inverted for. During the course, live demonstrations will be given that show practical implementations of the theory presented.

Course objectives

After attending the course, participants will have acquired a good understanding of the fundamental assumptions and limitations of state-of-the-art seismic migration. They will have been made familiar with the steps needed to extract quantitative property information from seismic data.

Course outline

• Short recap on complex transforms (Fourier, Laplace, Radon)
• Derivation of the acoustic wave equation
• Derivation of wavefield extrapolation equations, forward and backward in space and time
• The imaging condition and derivation of expressions for image amplitudes
• Inversion of image amplitudes for media properties

Participants' profile

Geophysicists from oil & gas (service) companies, or geophysicists from academia, involved in R&D.

Prerequisites

Participants should have a basic understanding of the seismic method as well as familiarity with mathematical tools like complex numbers and integrals.

Prof. Dr Dries Gisolf graduated from the Delft University of Technology in 1971 and obtained his PhD at the University of Utrecht in 1975. In 1976 he joined Shell International Research Co. in Rijswijk, The Netherlands, as a seismic data processing geophysicist. Between 1980-2000 he held various positions for Shell in Oman, The Netherlands, Australia, Malaysia and Nigeria. Throughout his career with Shell he was involved in acquisition, processing and interpretation of seismic data, with an emphasis on quantitative prediction of reservoir properties. In September 2000 he was nominated as Professor of Acoustical Imaging and Sound Control at the Faculty of Applied Sciences at the Delft University of Technology. After retiring from TU Delft in 2010, he co-founded Delft Inversion in 2012, a service company providing high-resolution reservoir oriented inversion services to the oil and gas industry.

Explore other courses under this discipline:

Full Waveform Inversion in an Anisotropic World. Where Are the Parameters Hiding?

Instructor: Prof. Tariq Alkhalifah (KAUST)

The course starts by introducing the fundamentals of full-waveform inversion (FWI) starting from its basic definition. It focuses on the model update issues and provides analysis of its probable success in converging to a plausible model. In the course we will discuss the many challenges we face in applying FWI on seismic data and introduce modern day proposed solutions to these challenges. The focus of the course will be on FWI applied to anisotropic media. As a result, the course will also introduce anisotropy, its optimal parametrization and wavefield simulation in such media. Practical multi-parameter inversion for anisotropic parameters requires an optimal FWI setup. We will discuss such a setup, which includes the proper parametrization of the medium and data access scheme necessary for a potential convergence to a plausible anisotropic model.

Principles and Applications of Seismic Interferometry and Ambient Noise Seismology in Hydrocarbon Exploration

Instructor: Dr Gerard Schuster (KAUST)

This one-day course is designed for a broad range of seismic researchers, data processors, and interpreters working in the petroleum industry. The course teaches the principles of seismic interferometry, ambient noise seismology and their applications to surface seismic, VSP, and OBS data. The ultimate objectives are to enable geophysicists to evaluate the potential of seismic interferometry in uniquely solving their problems.

Seismic Diffraction – Modelling, Imaging and Applications

Instructors: Prof. Evgeny Landa (Tel Aviv University) and Dr Tijmen Jan Moser (Moser Geophysical Services)

Diffractions have been identified as the key seismic manifestation of fractures and other small-scale reservoir heterogeneities. This two-day course will present the current state-of-the-art of diffraction technology and put this in context by a review of its past developments. The course will cover both forward diffraction modeling and diffraction imaging. Case studies of diffraction imaging will be presented covering applications in seismic exploration and other areas of geoscientific interest.

Applied Depth Imaging

Instructor: Dr Ruben Martinez (Reservoir Geoscience)

This course has two main segments. In the first segment, the participant will understand the basic concepts behind the tools commonly employed in velocity model building and depth migration.
In the second segment, the participant will learn how to use these tools for building velocity models and generate seismic images in depth using practical work flows for a variety of complex geologic scenarios. At the end of the course, an overview of the emerging depth imaging technologies is presented.

Beyond Conventional Seismic Imaging

Instructor: Prof. Evgeny Landa (Tel Aviv University)

While depth imaging play an increasing role in seismic exploration, data analysis and imaging in time domain play an important role. Moreover, for complex models that request the use of prestack depth migration, time imaging usually constitutes a key first step. The proposed course discusses: a) data analysis and imaging based on new procedures such as Multifocusing and Common Reflection Surface; b) diffraction Imaging based on diffracted energy targeting to image small scale subsurface objects; c) imaging without precise knowledge of the subsurface velocity model (path summation); d) pitfalls and challenges of seismic inversion.

Seismic Depth Imaging and Anisotropic Velocity Model Building

Instructor: Mr Etienne Robein (ERT)

The course will present in simple terms (cartoons rather than equations!) the principle of different techniques in each class of methods (Kirchhoff, Beam Migrations, WEM, RTM), while pointing out their respective merits and limitations. Similarities and differences between Time- and Depth-Imaging will be briefly reminded. In parallel, special emphasis is put on methods used to build the necessary anisotropic velocity models. Both Ray-based techniques (linear and non-linear tomography) and wavefield extrapolation-based ones, including Full Waveform Inversion, are addressed.

Full-Waveform Inversion for High-Resolution Reservoir Characterization

Instructor: Prof. Dr Dries Gisolf (Delft Inversion)

This two-day course will start with an introduction and a short recap on complex integral transforms (Fourier, Laplace, F/K and linear Radon). Followed by topics on: - The acoustic wave equation in inhomogenous media - Integral representations of the acoustic wave equation; Kirchhoff-Rayleigh and the Scattering Integral (Lippmann-Schwinger) - The AVO data model; Zoeppritz reflection coefficients - Linear inversion of AVO data including regularisation; synthetic and real data examples - The non-linear data model for inversion; data equation and object equation; iterative, multiplicatively regularised inversion - Applications based on an elastic full-wavefield non-linear data model; realistic synthetic reservoir study, real data case studies including low-frequency model extraction and seismic-to-well matching. Synthetic time-lapse example.

Migration and Velocity Model Building

Instructor: Mr Piet Gerritsma (Gerritsma Geophysical Training and Consultancy)

The process of migration, whereby a proper image in time or depth of the subsurface is obtained, is directly related with the velocity model that both serves as input for the migration process as well as is the result of such a migration. Therefore migration and velocity model building are intimately related processes and often applied in an iterative mode. This course gives an overwiew with theory and implementation of the representative migration algorithms as well as of the multitude of ways to build and update subsurface velocity models.