The Interpreter’s Guide to Depth Imaging

Scott MacKay

Instructors: Scott MacKay
Date: November 3 - 4, 2020
Duration:  2 days
Members (early bird/price): CAD$ 850/1000 (plus GST)
Non-members (early bird/price): CAD$ 1050/1200 (plus GST)
Location: TBA
Time: TBA


Scott MacKay is a petroleum geoscientist specializing in geophysics and geology, with extensive oil and gas exploration and exploitation experience. He started with a major oil company as an Exploration Geophysicist in Denver, developing structural and stratigraphic plays in the Williston and other Rocky Mountain Basins. He then joined the oil company’s Special Projects group in Houston as an Exploration Advisor, integrating the efforts of multidisciplinary teams in areas including the North Slope, Offshore Africa, North Sea, Colombia, and the Gulf of Mexico. After ten years, he joined what is now Schlumberger-WesternGeco as a Research Geophysicist developing advanced methods for depth migration. He was soon appointed Manager of R&D for WesternGeco where he also served as World-wide Coordinator for Depth Imaging, Time-lapse (4D) Reservoir Characterization, and Multicomponent Imaging. He was made a Schlumberger Advisor in 2003 and has five U.S. patents and many publications on applying innovative and practical solutions to seismic imaging issues.

Scott became an independent geophysical consultant in 2003, working domestic and international interpretation projects. He is experienced with Kingdom and Petrel for detailed evaluations and prospect generation. He also advises/mentors/trains O&G companies in applying appropriate seismic imaging technologies and interpretation techniques for play evaluation and risk reduction. He also specializes in managing anisotropic depth migration projects that span complex structure to subtle resource plays to quantify reservoir quality using advanced attributes including AVOAz (HTI) inversion. Recently, he has created advanced machine-learning estimations of Oil and Gas EURs from seismic and reservoir-model properties as part of several multidisciplinary development teams


An interpreter-oriented approach to the theory and practical applications of prestack depth imaging. The course begins with understanding the nature of velocity fields and practical approaches to velocity representation. Time-to-depth conversion is reviewed as a prelude to understanding the limits and pitfalls of time migration. The course then transitions to an intuitive overview of depth migration theory, Kirchhoff to RTM options, tomographic velocity updates, and full-waveform inversion.

The second day of class introduces intuitive quality controls and quantitative spreadsheet tools to plan and ensure stable depth solutions during the iterative depth-imaging process. The incorporation of horizon interpretations and well tops to constrain anisotropic depth migration is reviewed together with more advanced database validation methods. A robust approach to well-top calibration of the final depth cubes is addressed, as are statistical methods (freeware provided) for estimating depth uncertainty away from well control. Finally, the course reviews advanced attributes derived from depth imaging, including inversion for azimuthal amplitudes to yield lithologic and stress-field (fracture) properties.

Learner Outcomes: Participants will gain an understanding of how to effectively design, guide, and quality control depth-imaging projects in a variety of geologic settings and be able to:

  1. Appreciate time-to-depth conversion methodologies
  2. Differentiate between time and depth migration
  3. Distinguish between commonly-used migration algorithms
  4. Plan and evaluate migration-parameter tests
  5. Appraise method for velocity updating (tomography) appropriate for the geology
  6. Define target velocity resolution for tomography and related imaging grids
  7. Establish consistency between well tops and horizons in an interpretive database
  8. Plan and review QCs for iterative velocity updates
  9. Assess the methods used for determining anisotropic parameters
  10. Perform well-top calibration of depth imaging volumes
  11. Evaluate validity of advanced attributes

1: Review of Vertical Time-to-Depth Methods

  • Velocity field characterization
  • Single-layer depth conversion
  • Uncertainty analysis and pitfalls

2: Time and Depth Migration: Comparisons

  • General discussion of time and depth migration theory

3: Migration Algorithms: Theory and Practice

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

4: Migration: Parameter Selection

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

5: Tomographic Velocity Analysis

  • Layer- and grid-based ray methods
  • Full waveform inversion
  • Velocity update limitations and stability

6: Depth Imaging Grids

  • Depth/Velocity: Visualization (imaging) and velocity representation
  • Travel times/Propagation: Summation curves and/or wavefield extrapolation
  • CIP picking/Tomography: Data input to tomography and solution equations

7: Well/Seismic Database Validation

  • Determine data polarity and phase (synthetic ties and VSPs)
  • QCs to detect/resolve database discrepancies

8: Iterative Depth Imaging: Quality Control

  • QCs for creating the initial velocity model
  • Iterative tomographic updates and target-velocity resolution • Setting up an intuitive review of the iterative process

9: Anisotropy

  • Parameterization (Vz, delta, epsilon, VTI/TTI)
  • Velocity and parameter updates including directional anisotropy (HTI)

10: Well Calibration

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

11: Attributes

  • Poststack: amplitudes, curvature, coherence
  • Prestack: AVO, elastic inversion, brittleness
  • AVO with Azimuth and other Horizontal Transverse Isotropy (HTI) measurements