Practical Depth Conversion and Depth Imaging for the Interpreter

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