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    Oil and Gas Training Courses SLB NEXT

    Advanced Velocity Modelling | Blended course

    Migration algorithms are used to create images of the subsurface based on recordings at the surface of seismic (elastic) waves. A migration algorithm needs as input recorded pre-stack data and a (background) subsurface velocity model. Two migration methods exist: time and depth migration. Time migration assumes local lateral homogeneity and as a result assumes diffractions of hyperbolic shape. Depth migration does not assume lateral homogeneity and uses non-hyperbolic shaped diffraction curves as migration operators. Comparing time and depth migration shows that depth migration is more accurate, but also more sensitive to the velocity model. Note that when we mention a velocity input model for migration, it is a so-called velocity background model. The migration algorithm “collects” recorded data based on that background model and provides additional detail based on first order “Born scattering” theory. The accuracy in terms of resolution and correct amplitudes depends on the background model, the migration algorithm, and the acquisition geometry, which define the degree of illumination of each subsurface point. At each subsurface point the resolution can be investigated using so-called Point-Spread-Functions.

    This course is a blended course. It is lead remotely by the instructor that has daily direct interactions with the trainees for several hours. Trainees are self-learning for the rest of the day by doing exercises and going through the course material.  

    The course consists of presentations, videos, and exercises. The presentations, also made available in pdf, are animated power point shows. The videos are either related to the exercises or general, some related to professional societies. In the exercises the methods discussed in the presentations are applied using computer programs. The solutions are discussed. Also, the course contains quizzes which are meant to reinforce the learning. Each quiz consists of multiple-choice questions.  

     


    Agenda

    Part 1

    • Introduction / Biography
    • Geophysical Methods
    • Moodle
    • Velocities
    • NMO velocities
    • The reflection method (self-study)
    • Field record

    Part 2

    • DMO / DMO correction
    • Surface multiples
    • Internal multiples
    • Marchenko 
    •  Imaging  Velocities

    Part 3

    • Multiple Attenuation
    • Scale length
    • Effective media
    • Anisotropy

    Part 4

    • Joint inversion
    • FWI / FWI scales
    • EAGE E. Robein

    Part 5

    • TD conversion
    • PSF's
    • Fractures
    • Course evaluation

    Geophysicists involved in Acquisition & Processing


    A solid introduction to seismic acquisition and processing, followed by items directly related to deriving a velocity model needed as a background or “starting” model for imaging (migration) or for Full Waveform Inversion (FWI). These items are the different velocities used and their relationships, avoiding “multiple velocities”, the importance of scale length in relation to effective media velocities, anisotropy describing direction-dependence of velocities, phase, and group velocity and which one to use in studying AVA and the influence of fractures on anisotropic azimuthal velocity variation. 

    The course uses a Blended Learning approach based on a user-friendly Learning Management System, called Moodle. In Moodle different modules provide study material, videos, and exercises. The solutions to these exercises can be checked and if the correct solution cannot be found feedback will be given.

     


    A good understanding of the basics of seismic data acquisition and processing.


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