Geomechanical models need to incorporate a more reliable geological model concerning the overburden as well as the underburden sections. These aspects are more important when considering the flow simulation model and the injection and/or production of the field due to the surrounding rocks behavior and their responses against those ratios (injection/producing). Therefore, a 3D model is needed and the oil industry faces a great challenge: how to build this reliable model without seismic information? Or, how to use seismic properties with all their ambiguity to derive this 3D model? Special attention is necessary when observing the salt-section above the pre-salt reservoir in Santos Basin, Brazil, since the amplitude response is heavily influenced by the velocity model used for the migration process. The majority of these velocity models are considered non-geological as the main reasoning for them is only to produce a good image. To build a good seismic image, reproducing the geology is not needed: the only condition imposed on the model is that the migration operators applied using that model will focus the image. In other words, we could see a completely alien model regarding geology that focuses the image, and that model would be considered correct. In this paper, we will illustrate a way to build plausive velocity models fitting both the geology and the mathematics of the migration for a good seismic image. This allows for the use of the amplitude response for many purposes, including (but not limited to) deriving geomechanical properties, predicting the lithologies inside the evaporitic section and recursively building a new, more realistic velocity model.

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This paper focuses on the impact that reservoir geophysics has had on the production development of the Brazilian marine carbonate pre-salt fields starting from the first oil discovery in 2005 to 2011. The evolution of three main knowledge areas of reservoir geophysics technology will be detailed, namely: acquisition, processing and interpretation, all oriented towards reservoir characterization and monitoring. Seismic acquisition technology has experienced an increase in "information density" (seismic traces per square kilometer). In the seismic processing domain, the improvement of seismic algorithms and methodologies has allowed for better seismic data quality, resolution and imaging. In particular, the algorithms/techniques of 3-D multiple suppression and 3-D depth migration have significantly evolved in recent years. In the seismic interpretation area, geological contextoriented seismic attributes algorithms/methodologies have made possible better reservoir characterization in the deep and ultra deep-water Brazilian offshore basins.

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