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Oil & Gas Training
and Competency Development
Competency Management system SLB NEXT

Practical Depth Conversion and Depth Imaging for the Interpreter

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 will prioritize understanding the nature of velocity fields and will cover the practical approaches to velocity representation. Next, appropriate depthing methods will be presented in case history and exercise form. Basic and more advanced layer-based approaches will be reviewed with quantitative error analysis and its impact on topics ranging from well prognoses to volumetrics.

Depth imaging 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 will be an intuitive description of the theory and practical application of pre-stack depth imaging.  The instructor will demonstrate the quality controls used to ensure stable velocity solutions that yield geologically-reasonable results and meaningful attributes.

Day 1

Depth Conversion and Velocity

  • Module 1:  Overview of Depth Conversion
  • Module 2:  Sources of Velocity
  • Module 3:  Defining Velocity Types
  • Module 4:  Representation of Velocities

Learn the motivation for vertical time-to-depth conversion and the common sources of velocity information.  Review definitions and characteristics of velocities, as well as how to define velocities fields using vertical and spatial functions.

Day 2

Data Integration and Vertical Time-to-Depth Conversion

  • Module 5:  Well and Seismic Data Integration
  • Module 6:  Vertical Time-to-Depth Conversion (Basic)
  • Module 7:  Vertical Time-to-Depth Conversion (Advanced)

Focus on data integration and vertical time-to-depth conversion.  Learn how to understand the methods for linking well and seismic information. Additionally, cover the implementation of basic depth conversion using vertical functions and spatial corrections, as well as exploring depth conversion using more sophisticated methods.           

Day 3

Vertical Depth Conversion and Depth Migration  

  • Module 8:  Applications and Pitfalls of Vertical Depth Conversion
  • Module 9:  Acquisition and Time Processing
  • Module 10:  Time and Depth Migration: Comparisons       
  • Module 11:  Migration Algorithms: Theory and Practice

Learn about the accuracy of vertical time-to-depth methods and what happens when they fail.  Also, learn to appreciate the impact that acquisition and signal processing have on imaging, as well as the differences between time and depth imaging in context of the different depth migration algorithms.

    Day 4

    Parameter Selection, Velocity Analysis, Depth Imaging Grids, and Data Validation

    • Module 12:  Migration: Parameter Selection
    • Module 13:  Tomographic Velocity Analysis
    • Module 14:  Depth Imaging Grids
    • Module 15:  Well/Seismic Database Validation

    Review the impact of parameter selection for imaging and learn to understand the differences and resultant solutions from various approaches to tomography.  Discuss the different grids that need to be defined in depth imaging.  Most importantly, review methods for correcting the database prior to incorporating well control.

      Day 5

      Quality Control, Anisotropy, Well Calibration, and Attributes

      • Module 16:  Iterative Depth Imaging: Quality Control
      • Module 17:  Anisotropy
      • Module 18:  Well Calibration
      • Module 19:  Attributes

      Incorporate a set of fundamental review steps in depth imaging projects, and learn to appreciate the basic concepts for imaging and defining anisotropic parameters.  Review the basic QCs for stable integration with well control, ending the day with learning about utilizing attributes derived from depth imaging and subsequent inversion.

      Learning activity mix

      This course is aimed toward Geoscientists involved in seismic interpretation and subsequent time-to-depth conversion, in addition to incorporating pre-stack depth migration into their seismic evaluations. 

      Participants will gain an understanding of depth conversion methodologies and QCs for validity of methods used. Also, they will learn how to effectively design, guide, and quality control depth-imaging projects in a variety of geologic settings and be able to:

      • Assess the various sources and utility of velocities
      • Learn the types of velocities plus methods of defining and accessing them
      • Investigate the compatibility of well and seismic data using synthetics and other methods
      • Perform basic and advanced depth conversions of time data and characterize the errors
      • Judge the limits of vertical depth conversion with increasingly extreme geologic situations
      • Supervise initial time processing of data and methods to mitigate acquisition shortcomings
      • Assess the differences between time and depth migration
      • Characterize the underlying theory between ray and wave-equation methods
      • Parameterize migration algorithms
      • Appraise the form of velocity updating (tomography) appropriate for the geology
      • Establish target velocity resolution for tomography and associated grids (tomo cells, gathers...)
      • Validate and correct the database via well and seismic ties
      • Plan and review QCs for iterative velocity updates
      • Assess the method used for determining anisotropic parameters
      • Implement an optimal approach for calibrating well and seismic data
      • Evaluate attributes such as inversion and (HTI) directional stress and lithology estimates

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

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