Practical Depth Conversion with Petrel

Module 1:  Overview of Depth Conversion

* Learning Objectives and Importance:    

• Discuss goals for vertical time-to-depth conversion

* Topics:          

• Accuracies needed for  relative structure, well prognoses, volumetric estimates, and reservoir models
• Database validation
• Indicators for prestack depth migration (PSDM)

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

Module 2:  Sources of Velocity

* Learning Objectives and Importance:    

• Review sources of velocity information

* Topics:          

• Sonic logs, check shots, and VSPs
• Seismic (refraction, reflection)
• Inversion

* Exercises:  Analysis of various velocity data 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
• Velocity gradients

 * Exercises:  Various problems on relating velocity types and conversions. Petrel exercises.

Module 4A:  Functional Representation of Velocities

* Learning Objectives and Importance:    

• Define velocities fields using vertical functions

* Topics:          

• Velocity as a function of time and depth
• Implicit velocity representation via T-D functions
• Petrel Velocity Models with time and depth functions

* Exercises:  Various problems defining velocity fields in various domains

Module 4B:  Gridded Representation of Velocities

* Learning Objectives and Importance:    

• Define velocities fields using grids

* Topics:          

• Spatial velocity variations (lateral gradients)
• Creating an edited PSTM velocity model in Petrel

* Exercises:  Import SEG Y velocities to Petrel and forming a gridded model

Module 5:  Well and Seismic Data Integration

* Learning Objectives and Importance:    

• Understand methods for linking well and seismic information in Petrel

* Topics:          

• Sonic and density log editing
• Checkshot loading
• Establishing seismic data polarity and phase
• Database validation and QCs
• Creating synthetic ties

* Exercises:  Problem sets and interactive work sessions

Module 6:  Vertical Time-to-Depth Conversion (Single Layer)

* Learning Objectives and Importance:    

• Implement basic depth conversion using T/Z functions and/or Petrel Velocity Models

* Topics:          

• Simple, intuitive depth conversion (no velocity model)
• QC methods that define Time Depth Relationships (TDRs)
• Basic Petrel Velocity Models

 * Exercises:  Problem sets and interactive work sessions

Module 7:  Vertical Time-to-Depth Conversion (Multi-Layer)

* Learning Objectives and Importance:

• Explore advanced depth conversion with layer-based Petrel Velocity Models

* Topics:

• Geologic and data-driven modeling considerations
• Multi-layer options
• “Simple” thrust models
• Advanced Petrel Velocity Models

* Exercises:  Problem sets and interactive work sessions

Module 8:  Well/Seismic Database Validation

* Learning Objectives and Importance:    

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

* Topics:          

• Confirm database settings
• Review seismic data polarity, phase, and synthetic correlations
• Using basic depth-conversion QCs to encounter data discrepancies

* Exercises:  Extensive exercises on detecting and correcting errors and inconsistencies in the database

Module 9: Petrel Models and Uncertainty Analysis

* Learning Objectives and Importance:    

• Implement domain conversion and uncertainty analysis with Petrel Velocity and 3D Models

* Topics:          

• Evaluating depth uncertainty
  • Mean and standard deviation workflow (new)
  • Hidden well workflow
  • Stochastic velocity modeling
• Impact of structural uncertainty on volumetrics in 3D Models

* Exercises:  Various Petrel exercises

Module 10:  Pitfalls of Vertical Depth Conversion

* Learning Objectives and Importance: 

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

* Topics:          

• QCs and validity of vertical depth conversion
• Extreme geologic regimes
• Alternatives to vertical depth conversion

* Exercises:  Problem sets and interactive work sessions

Module 11:  Anisotropy and Depth Migration

* Learning Objectives and Importance:    

• Appreciate the impact of anisotropy on seismic velocities and depth imaging

* Topics:          

• Seismic anisotropy
• Parameterizing anisotropy (Vz, delta, epsilon, VTI/TTI)
• Industry approaches to anisotropic prestack depth migration (APSDM)
• Problems and promise of anisotropy for velocity definition and reservoir attributes

* Exercises:  Discuss impact of anisotropy on depth conversion and imaging

Module 12:  Calibration of Depth Migration with Wells

* Learning Objectives and Importance:    

• Learn basic approach for stable integration of depth-domain seismic (PSDM) with well control

* Topics:          

• Working in the time domain
• Updating the time/velocity model
• Conversion of time data to calibrated depth
• Optional: Map migration for dynamic calibration and uncertainty

* Exercises:  Various Petrel calibration exercises