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    Oil and Gas Training Courses SLB NEXT

    Practical Depth Conversion and Depth Imaging for the Interpreter | RILS format (Remote Instructor-Led Series)

    This is a Remote Instructor Led Series (RILS) training. The remote classroom delivery is a modality that takes advantage of the instructor led training content, while allowing the same content to be delivered remotely.
    All training sessions will be delivered online with no face-to-face classroom attendance. This class will be delivered in 4 to 6 hours daily sessions over 8 to 10 days

    Depth conversion of time interpretations is a basic skill set for interpreters. There is no single methodology that is optimal for all cases. The first part of this course emphasizes understanding the nature of velocity fields and practical approaches to velocity representation. Next, appropriate depth-conversion methods are presented in case history and exercise form. Basic and more advanced layer-based approaches are reviewed with quantitative uncertainty analysis and its impact, ranging from well-top prognoses to volumetric estimations.

    Depth migration should be considered an integral component of interpretation. If the results derived from depth imaging are intended to mitigate risk, the interpreter must actively guide the process. The second part of this course is an intuitive description of the theory and practical implementation of prestack depth imaging. The course focuses on the interpreter-oriented quality controls used to ensure stable velocity solutions and geologically-reasonable results. The course concludes by outlining the flow for calibrating the depth-migration volumes to well tops and the formation of meaningful seismic attributes


    RILS course content

    Day 1:  Practical Depth Conversion and Depth Imaging for the Interpreter 

    Module 1:  Overview of Depth Conversion

    * Learning Objectives and Importance:           

    • Discuss the motivation for vertical time-to-depth conversion

    * Topics:

    • Why do we depth convert time interpretations?
    • Accuracies of relative structure, well prognoses, volumetrics and reservoir models

    * Exercises:  Discussions on student experiences with time-to-depth conversion 

    Module 2:  Sources of Velocity

    * Learning Objectives and Importance:           

    • Review common sources of velocity information

    * Topics:

    • Sonic logs, check shots, and VSPs
    • Seismic refraction and  reflection data
    • Full waveform inversion
    • Model based

    * Exercises:  Analysis of various velocity source types 

    Module 3:  Defining Velocity Types

    * Learning Objectives and Importance:           

    • Review definitions and characteristics of velocities

    * Topics:

    • Types of velocities
    • Conversion of velocity types
    • Compactional and layered geologies

     * Exercises:  Various problems on relating velocity types and conversions                                    

    Module 4:  Representation of Velocities

    * Learning Objectives and Importance:           

    • Define velocities for depth conversion using vertical/spatial functions and grids

    * Topics:

    • Velocity as a function of depth
    • Velocity as a function of time
    • Spatial velocity variations (lateral gradients) and grids

    * Exercises:  Various problems defining velocity fields in various domains 

    Module 5:  Well and Seismic Data Integration

    * Learning Objectives and Importance:           

    • Understand methods for linking well and seismic information

    * Topics:

    • Creating synthetic seismograms: “Wiggle” and P Impedance
    • Establishing data polarity and phase
    • Correlating reflections with well tops (synthetic ties)

    * Exercises:  Problem sets and interactive work sessions

     

    Day 2:  Practical Depth Conversion and Depth Imaging for the Interpreter 

    Module 6:  Vertical Time-to-Depth Conversion (Basic)

    * Learning Objectives and Importance:           

    • Implement basic depth conversion using vertical functions and spatial corrections

    * Topics:

    • Single-layer methods (direct depth conversion)
    • Handling spatial velocity variations (lateral gradients)
    • QC methods

     * Exercises:  Problem sets and interactive work sessions 

    Module 7:  Vertical Time-to-Depth Conversion (Advanced)

    * Learning Objectives and Importance:

    • Explore depth conversion with more sophisticated methods

    * Topics:

    • Multi-layer methods
    • Editing velocities
    • Creating velocity models (various platforms)

    * Exercises:  Problem sets and interactive work sessions 

    Module 8:  Pitfalls of Vertical Depth Conversion and Uncertainty Analysis

    * Learning Objectives and Importance: 

    • Understand accuracy of vertical time-to-depth methods and when they fail

    * Topics:

    • Extreme geologic regimes
    • Shallow velocity anomalies and overpressure
    • Uncertainty analysis (including freeware for Stochastic Modeling)

    * Exercises:  Problem sets and interactive work sessions 

    Module 9:  Acquisition and Time Processing

    * Learning Objectives and Importance:          

    • Understand the impact of acquisition and signal processing on imaging

    * Topics:

    • Acquisition considerations
    • Refraction and reflection statics
    • Relative amplitude preservation
    • Interpolation and migration-amplitude corrections

    * Exercises:  Discussions on acquisition and data processing practices and experiences 

     

    Day 3:  Practical Depth Conversion and Depth Imaging for the Interpreter 

    Module 10:  Time and Depth Migration: Comparisons       

    * Learning Objectives and Importance:           

    • Obtain an appreciation for the differences between time and depth imaging       

    * Topics:

    • Intuitive discussion of time and depth migration theory

    * Exercises:  Industry examples and class discussions of student experiences 

    Module 11:  Migration Algorithms: Theory and Practice       

    * Learning Objectives and Importance:          

    • Convey an intuitive understanding of the different depth migration algorithms

    * Topics:

    • Kirchhoff, Gaussian Beam, 1-way Wave Equation and 2-way (Reverse Time)     
    • Offset and angle domains for Common Image Point Gathers
    • Anisotropy and Multi-component

    * Exercises:  Case history reviews 

    Module 12:  Migration: Parameter Selection

    * Learning Objectives and Importance:          

    • Review the impact of parameter selection for imaging

    * Topics:

    • Kirchhoff travel times and Wave Equation imaging conditions
    • Amplitudes, aliasing, and aperture
    • Regularization (interpolation) and Equalization (migration weighting)

    * Exercises:  Ray trace, amplitude, aliasing, and aperture with spreadsheet calculations 

    Module 13:  Tomographic Velocity Analysis and FWI

    * Learning Objectives and Importance:          

    • Understand the differences between various industry approaches to velocity updating

    * Topics:

    • Layer- and grid-based ray methods     
    • Full waveform inversion: Near-surface and deep velocity models
    • Non-tomographic methods

    * Exercises:  Simple tomographic solution examples to demonstrate issues in stability and uniqueness

       

    Day 4:  Practical Depth Conversion and Depth Imaging for the Interpreter 

    Module 14:  Depth Imaging Grids

    * Learning Objectives and Importance:          

    • Review the different grids that need to be defined and solved for in depth imaging

    * Topics:

    • Image/Velocity: Visualization and velocity representation
    • Travel times/Propagation: Summation curves and/or wavefield extrapolation
    • CIP picking/Tomography: Data input to tomography and solution grid

    * Exercises:  Various problem sets with spreadsheets 

    Module 15:  Well/Seismic Database Validation

    * Learning Objectives and Importance:          

    • Appreciate the need to review and correct the database prior to  incorporating well control into PSDM

    * Topics:

    • Data exchange and QC between interpreter and processor
    • Basic QCs to encounter data discrepancies

    * Exercises:  QCs presented with associated exercises 

    Module 16:  Iterative Depth Imaging: Quality Control

    * Learning Objectives and Importance:          

    • Incorporate a set of fundamental review steps in depth imaging projects

    * Topics:               

    ·         QCs for creating the initial velocity model

    ·         Reviewing iterative tomographic updates and target-velocity resolution

    ·         Setting up an intuitive review of iterative process

    *Exercises:  QCs presented with associated exercises 

      

    Day 5:  Practical Depth Conversion and Depth Imaging for the Interpreter 

    Module 17:  Anisotropy and Depth Migration

    * Learning Objectives and Importance:          

    • Appreciate basic concepts for imaging and defining anisotropic parameters

    * Topics:

    • Seismic anisotropy
    • Parameterization (Vz, Delta, Epsilon, VTI/TTI…)
    • Imaging methodologies
    • Velocity and parameter updates
    • Azimuthal anisotropy (HTI)

    * Exercises:  Review and discuss benefits and pitfalls of attributes from isotropic and anisotropic PSDM 

    Module 18: Well Calibration of Depth Migration

    * Learning Objectives and Importance:          

    • Learn basic QCs for stable integration with well control

    * Topics:

    • Working in the time domain
    • Updating the time/velocity model
    • Conversion of time data to calibrated depth
    • Uncertainty measures (Stochastic prognoses)

    * Exercises:  Various calibration exercises in spreadsheet and map form 

    Module 19:  Seismic Attributes

    * Learning Objectives and Importance:          

    • Understand the stability and resolution of depth imaging

    * Topics:

    • Poststack: amplitudes, curvature, coherence, Ant Tracking
    • Prestack: AVO, elastic inversion, brittleness
    • AVO with Azimuth and other Horizontal Transverse Isotropy (HTI) measurements
    • Practical applications of machine-learning algorithms

    * Exercises:  Review benefits of attributes from depth imaging


    This course is of importance to geoscientists involved in seismic time interpretation, time-to-depth conversion, and the planning and interpretation of depth-migration projects. Participants should have a basic understanding of seismic processing and interpretation.

    Participants will gain an understanding of depth-conversion methodologies, QCs for validating the methods employed, and tools for quantitative uncertainty estimation. They will also learn how to effectively design, guide, and QC depth-imaging projects in a variety of geologic settings and be able to:  

    • Evaluate types of velocity data and methods for velocity definition and use
    • Investigate the compatibility of well and seismic data
    • Perform basic and advanced depth conversions of time data with uncertainty analysis
    • Understand the key differences between time and depth migration
    • Differentiate between ray and wave-equation methods
    • Appraise the form of velocity updating (tomography/FWI) appropriate for the geology
    • Establish a reasonable target velocity resolution for tomography
    • Validate and correct the database via well top and seismic-interpretation ties
    • Plan and assess QCs for iterative velocity updates
    • Appraise the methods used for determining anisotropic parameters
    • Implement an optimal approach for calibrating well and seismic data
    • Evaluate attributes such as inversion and (HTI) azimuthal stress and lithology estimates
    • Review practical aspects of machine-learning classification and estimation



    A basic background in geophysical interpretation, as well as some experience in time-to-depth conversion of seismic time horizons. 

    Textbook and Exercise book provided, interactive demonstrations of freeware, no computer needed.


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