Interval Velocity Estimations from Seismic Reflection Data

Thesis Abstract

The research project was carried out to study the estimations of interval velocity from seismic reflection data of the acoustic P waves inside the Earth using the method of time migration which is necessary for obtaining seismic images in regular Cartesian coordinates. The main goals of the research work were to develop algorithms to convert time-migration velocities to true seismic velocities, and to convert time-migrated images to depth images in regular Cartesian coordinates. The results were the established theoretical relation between the true seismic velocities and the 'time-migration velocities' using the paraxial ray tracing, the formulated appropriate inverse problem describing the relation between time-migration velocities and depth velocities, and the developed numerical algorithms to solve regularized versions of the formulated equations which can be used to recover smoothed velocity variations. The developed algorithms include the efficient time-to-depth conversion algorithms, the level set and ray tracing algorithms for transforming Dix velocities into interval velocities. These algorithms are applied to both two- and three-dimensional problems, and they are tested on a collection of both synthetic and field data, which yielded improved seismic images.