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

Module 2:  Sources of Velocity

Learning Objectives and Importance:    

• Review sources of velocity information

Topics:          

• Sonic logs, check shots and VSPs
• Refraction and reflection seismic
• Full Waveform Inversion
• PSDM Tomography

Module 3:  Defining Velocity Types

Learning Objectives and Importance:    

• Review definitions and characteristics of velocities for Petrel representation

Topics:          

• Types of velocities and Petrel representations (Templates)
• Basic conversion of velocity types (e.g. RMS to Interval)
• Import and conversion of velocity text files
• Creating Petrel seismic velocity cubes from text files

Module 4:  Functional Representation of Velocities

Learning Objectives and Importance:    

• Define velocities fields using vertical functions

Topics:          

• Implicit velocity representation via Time-Depth functions
• Velocity as a function of time (V0+KT) and basic database QCs
• Velocity as a function of depth (V0+KZ) from well-tie Time Depth Relationships (TDRs)
• Petrel Velocity Models with time and depth functions

Exercises:  Various problems defining velocity fields in various domains

Module 5:  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 6:  Vertical Time-to-Depth Conversion (Basic)

Learning Objectives and Importance:    

• Implement well-top calibrated depth conversion using T/Z functions and/or Petrel Velocity Models

Topics:          

• Simple, intuitive depth conversion (no velocity model)
• V0+KT Lookup plus Well Adjustment
• QC methods that define Time Depth Relationships (TDRs)
• Basic Petrel Velocity Models
• V0+KT
• Seismic velocities
• V0+KZ from well TDRs
• Time to Depth QCs

Module 7:  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
• Check shot loading and QC
• Establishing seismic data polarity and phase (the wavelet)
• Creating synthetic seismogram well-tie correlations
• Image volumes (“wiggle trace”)
• Inversion volumes (creating P Impedance logs and synthetics)
• Issues with synthetic ties

Module 8:  Vertical Time-to-Depth Conversion (Advanced)

Learning Objectives and Importance:

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

Topics:

• Geologic and data-driven modeling considerations
• Multi-layer Petrel Velocity Models
• Structure and Isopach QCs
• “Simple” thrust models (forming complex models in Petrel)

Module 9:  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
• Using basic depth-conversion QCs to encounter data discrepancies

Module 10: 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)
• Stochastic velocity modeling
• Hidden well workflow

Module 11:  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 (depth migration, image rays, and map migration)

Module 12:  Calibration of Depth Migration with Well Tops

Learning Objectives and Importance:   

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

Topics:          

• Working in the time domain
• Conversion of PSDM depth deliverables to time
• Creating the calibrated time/velocity model (the anisotropic Vz model)
• Database QC: surface versus well-top cross plots
• Conversion of time data (seismic/surfaces/faults) to well-top calibrated depth
• Petrel Z-Z Model for well-top calibrated depth