f Advanced 3D macro-model estimation: The Sistre Project

Getting a reliable depth image of the subsurface requires the identification of the main geological bodies beneath the surface of the earth, the estimation of the wave propagation velocities through these bodies, and an accurate positioning in depth of the interfaces which separate the geological layers. The exploration industry needs in the field of macro-model estimation have recently evolved from the conventional 2D framework towards the more attractive 3D framework. As a consequence, our geophysical industry must he prepared to offer reliable tools which make it possible to estimate structurally complex 3D geological bodies from seismic data. Several authors have reported methods to carry out three-dirnensional macro-model estimation using ray-tracing techniques and traveltime inversion techniques (Fawcett (1983), Chiu and Stewart (1987), and Guiziou and Haas (1988) ). However, these methods are limited to layer-cake-type subsurface models.