Advanced Depth Migration Techniques

Audience

The course is designed for geophysicist with basic depth imaging experience requiring additional knowledge on the techniques used in depth imaging

Content

This course begins with a review of the basic principles of depth migration, isotropic and anisotropic (VTI, TTI) operators and the forward and inverse problem.

This is followed by a discussion of typical imaging problems, acquisition limitations, illumination issues, offsets and interbed multiples and the evolution of ray based and wave equation migration techniques.

The commonly used single arrival ray based migration; Kirchhoff, is reviewed with travel-time map computation and the difference between the travel times being looked at. Extending to multi-arrival, Gaussian beam migration is presented with its benefits highlighted. The principles of operation are followed by the workflow with key parameters being explained. Reverse time migration, a method based on wave equation, is introduced through an initial look at methods of solving the wave equation. The benefits and limitation of the method are explained prior to delving into the workflow. Key parameters and consideration are highlighted together with methods of quality control. Finally, tomography is explained and the velocity model update via non-linear tomography is discussed.

The key topics covered are
• Review of the basic principles of depth migration
• Isotropy and anisotropy
• Imaging considerations
• Ray based Kirchhoff migration and travel time computation
• Multi arrival ray based Gaussian beam migration, the principles and workflow
• The wave equation and reverse time migration
• Reverse time migration, the inputs domain, imaging principals, and workflow consideration
• What is tomography?
• Non-linear tomography inversion and kinematic de-migration
• Velocity model update workflow

Learning Objectives

• Be able to name the various techniques used for depth modeling used in the industry today
• Know the key difference between the various methods and the benefits each one holds
• Know how to perform a Kirchhoff migration and a Gaussian beam migration
• Know how to carry out a reverse time migration
• Understand the key components of the tomographic inversion sequence
• Capable of generating and updating an anisotropic model using tomographic sequence