Tomographic Inversion of Focusing Operators

Abstract

Seismic images of the structure of the earth are a prerequisite for finding new hydrocarbon reservoirs. The quality of a seismic images is highly dependent on the accuracy of the velocity model of the subsurface. Conventional imaging consists of an iterative process between obtaining the image using a velocity model, and updating this model by investigating the properties of the image. The Common Focal Point (CFP) method makes it possible to analyze and treat seismic data in a fundamentally different way as it uses a two-step approach: 1) two-way reflection data are transformed into one-way data by estimating focusing operators, and 2) these focusing operators are used to estimate the velocity model by tomographic inversion. This second step, the tomographic inversion of focusing operators, is the subject of this thesis. This research contains two important new aspects. First, the use of focusing operators in (3D) velocity model estimation. Second the data-driven approach of the method. Some additional concepts like the inclusion of a priori information, the joint inversion of P and S-wave operators, and the new concept of the focal point clouds, by which the adequacy of the velocity model can be analyzed, are also addressed. After evaluation of the method of tomographic inversion of focusing operators on both synthetic and real data it can be concluded that the method results in accurate velocity models and is capable of dealing with complex subsurface models.