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Image Ray Tomography
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 73rd EAGE Conference and Exhibition incorporating SPE EUROPEC 2011, May 2011, cp-238-00532
- ISBN: 978-90-73834-12-5
Abstract
Tomographic methods for the determination of velocity models using kinematic wavefield attributes strongly depend on the accuracy of the attributes. The Common-Reflection-Surface method applied to prestack data provides the attributes already with high quality. However, one difficulty of the CRS method is the treatment of diffractions and triplications, especially when located close to reflections. In such areas the quality of the attributes is not sufficient and, therefore, velocity model building with Normal Incident Point wave tomography does not provide an optimum result. Thus, it is reasonable to extract the kinematic wavefield attributes in the time-migrated domain. The Common-Reflection-Surface method applied to the time-migrated data approximates the zero-offset traveltime as a second-order Taylor expansion in the vicinity of the image ray. The data vector for the inversion contains the wavefront curvatures of the image rays. The model vector is calculated by dynamic ray-tracing along central image rays. The inversion problem is solved iteratively by computing the least-squares solution to the locally linearized problem during each iteration step. The required Frechet derivatives for the tomographic matrix are calculated with ray perturbation theory.