The primary objective of this course is to provide a broad and intuitive understanding of seismic imaging concepts and methods that enables geoscientists to make the appropriate decisions during acquisition, processing, imaging, and interpretation projects.
Seismic images are the basis of crucial exploration, development, and production decisions. Optimal use of these images requires a full understanding of the seismic imaging processes that create them, from data acquisition to the final migration. The primary objective of this course is to provide a broad and intuitive understanding of seismic imaging concepts and methods that enables geoscientists to make the appropriate decisions during acquisition, processing, imaging, and interpretation projects. Another objective is to expose the audience to current trends in imaging research and empower them to adopt new technologies quickly.
Prerequisites (Knowledge/Experience/Education Required)
The course is designed to be followed by anyone with a broad geoscience background: no specific detailed fore-knowledge is required, although a familiarity with geophysical, exploration and drilling terminology will be useful.
The course is organized in five parts. The first lecture introduces the fundamental concepts of seismic imaging. The remaining lectures focus on the solutions to four crucial problems encountered in practical application of 3D seismic data: 1) choice of the most effective migration algorithm, 2) estimation of the velocity model, 3) principle of waveform inversion, and 4) poor image quality caused by irregular and inadequate data spatial sampling and incomplete subsurface illumination
- Introduction to 3-D seismic imaging
- Commonly used data-acquisition geometries and their impact on imaging
- Seismic imaging as a data focusing process and Kirchhoff migration methods
- Principles of wavefield-continuation equation migration
- The relationship between seismic velocity and migration
- A user guide to the migration toolbox
- Time vs. depth migration
- Kirchhoff depth migration
- Depth migration by wavefield-continuations:
- Anisotropic migration
- Current trends in depth migration (Reverse Time Migration)
- The never-ending quest for the perfect velocity model
- Basic methods for velocity estimation (velocity spectra, Dix equation)
- Velocity estimation and complex structure
- Principles of reflection traveltime tomography
- Migration Velocity Analysis (MVA)
- Introducing geological knowledge in the MVA process
- Introduction to imaging as a waveform inversion process
- Principle of waveform inversion
- Linearized waveform inversion and Least-Squares Reverse Time Migration (LSRTM)
- Full waveform inversion
- Wave-Equation Migration Velocity Analysis (WEMVA)
- Time-lapse imaging by waveform inversion
- Imaging, aliasing and incomplete subsurface illumination
- Spatial aliasing and imaging artifacts caused by inadequate spatial sampling
- Avoiding aliasing in Kirchhoff migration and wavefield-continuation migration
- Imaging artifacts caused by irregular data geometry and incomplete illumination
- Illumination maps: how to use and not abuse them.
- Application of approximate regularized inversion to imaging enhancements:
- Data-domain methods (Data geometry regularization)
- Model-domain methods (Imaging by least-squares migration)
- Choose the most effective type of seismic data acquisition to achieve the subsurface imaging goals of a project.
- Determine which migration method is the most appropriate to image the target of interest in a project.
- Select among the imaging workflows proposed by a seismic contractor which one is the most likely to yield an accurate velocity model and a useful image.
- When presented with a failure of a seismic imaging project, be able to suggest alternative approaches that can yield better results.