Velocities, Time-imaging and Depth-imaging: Principles and Methods

There are numerous textbooks and publications on seismic processing, and in particular migration. However, we do not know of any work giving an overview of the many types of 'velocities' used in Seismics and how they relate to the different methods involved in the creation of the seismic image.
This text reviews the imaging methods used in the oil and gas industry today, with a unique emphasis on this relationship between imaging and velocity. It addresses imaging in both time and depth domains, spanning the range of complexity from NMO correction to sophisticated pre-stack migrations. Recent tools, such as inversion and demigration, and new directions, e.g. accounting for anisotropy have also been tackled. The work is comprehensively illustrated with a total of more than 200 figures.
The book should therefore be of interest to students looking for a complete introduction to seismic imaging techniques and their respective theoretical and practical merits and limitations. It is equally written to serve as a reference book for industry professionals, both generalists and specialists, who wish to revise standard techniques or take a look at some of the newer developments. In particular, interpreters, who participate in more and more tasks involving seismic velocities, will find answers to many of the questions which arise when, for example, tying seismic images to wells, creating post- and pre-stack time migration velocity fields, building a velocity model for depth migration or simply converting maps from time to depth.
The book is divided into four major sections:
Chapters 1-3 are dedicated to the fundamental concepts that lie behind elastic wave propagation within the subsurface, the velocity of such propagation, and the seismic imaging process itself. They should be considered as a (long!) introduction and most of the concepts will be used subsequently.
Chapters 4-6 outline the specific imaging principles: NMO, DMO, stack and post-stack migrations. In these chapters important ideas such as ‘migration in time’ and ‘migration in depth’ are presented. We also aim to clarify the relationship between velocity and migration, going on to show how improved velocity information leads to better seismic imaging, which in turn allows a better estimation of subsurface propagation velocities.
Chapter 7 generalizes the migration concepts from ‘post-stack’ to ‘prestack’ in both the time domain and the depth domain.
Chapter 8 recapitulates practical issues in estimating depth from the seismic image and the seismic velocity, and matching these with borehole data.