This course is about seismic velocities, especially as related to seismic processing and 3D seismic exploration. Each presentation contains hand-created graphics, illustrated to explain the concepts. The presentations are separated into 9 individual presentations. The users will better understand the importance of proper seismic velocities and how doing it wrong can severely harm your interpretation. But how using the right velocities, in the right procedures, can greatly help image the subsurface as well as find horizontal layering and vertical fractures.
This course is about seismic velocities, especially as related to seismic processing and 3D seismic exploration. Each presentation contains hand-created graphics, illustrated to explain the concepts. The presentations are separated into 9 individual presentations. The users will better understand the importance of proper seismic velocities and how doing it wrong can severely harm your interpretation. But how using the right velocities, in the right procedures, can greatly help image the subsurface as well as find horizontal layering and vertical fractures.
Parts 1 & 2: Introduction to standard NMO velocities and multiples. How are velocities picked and how to avoid multiples.
Parts 3-5: Fundamental differences between time migration velocities and depth migration velocities. Why depth migration is required for areas with lateral velocity variations. How migrated gathers are affected. What are velocity sags and pull-ups? How to build a traditional sub-salt velocity model.
Parts 6 & 7: Tomography and Full Waveform Inversion. How they are used in depth migration to improve psdm velocity fields. How are gathers affected before and after tomo and fwi? Simple graphics explain each concept.
Parts 8 & 9: Anisotropy. VTI, HTI. Anisotropy can be used to help find horizontal rock layering and vertical fracturing. How does anisotropy look on seismic data?
Bonus - Part 10: merging multiple volumes
Additional Bonus. I narrate a real 2D land seismic project. You will see the geological motivation behind the project, the seismic acquisition and equipment, the key steps in the seismic processing and images of the final migration. You will understand why most areas of the results are terrific while a small portion is poorly imaged. The project is located in an area of sparse seismic activity - South Dakota in USA.
This introduction to seismic velocities will show how seismic data is acquired in the field (land or marine). It will show how reflected events look on gathers. It will show why picking accurate velocities is important and how accurate velocities produce flat gathers.
The students will learn the fundamental differences between velocities used for time migration and used for depth migration. How inaccurate velocities in depth migration can introduce wrong depths and wrong dip.
The students will understand why depth migration is needed to image geology in areas of lateral velocity changes.
Students will learn the traditional top-down procedure for building a deep-water, sub-salt velocity model used in depth migration.
Students will learn about tomography. How it uses non-flat gathers to update the depth velocity field.
Students will learn the basics of full waveform inversion, and how it optimizes velocities used for depth migration. Plus how fwi differs between land datasets and marine datasets.
Students will learn about vertical fractured anisotropy, rocks with fractures. How it's seen on seismic gathers and how 5D interpolation helps.
I show some of the often-hidden details when merging 2 or more surveys together. Often neighboring surveys are acquired differently - different fold, vibroseis sweeps, inline/xline grids. The surveys gets merged into a seemingly-uniform grid. How can the interpreter reference these differences - to distinguish seismic character changes due to geology or due to changing seismic acquisition?
You'll learn some of the basic terms and definitions of common seismic nomenclature. Nothing fancy, just the basics.
You'll learn why refraction statics is done on land seismic processing projects. You'll learn the absolute minimum (it can get complicated!) on how tomo refraction statics is done. Apologies - only graphical images are shown as have not received permission to show real dataset examples.
This is a simple way to estimate seismic interval velocities when picking rms velocities. The legendary Fred Hilterman taught me this technique.
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