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.
Advances in acquisition techniques and in processing workflows have made seismic amplitude more reliable, and, consequently, the quantitative information has become more trustworthy. Rock physics and seismic inversion are essential tools for reservoir characterization. Rock physics improves our knowledge about how the variations of reservoir properties affect the seismic response. Seismic inversion is a tool to obtain 3D volume of elastic properties. Combining the static information from seismic and well data is the first approach for reservoir characterization. Data from core, well log, and laboratory tests help to mitigate the risk associated with seismic interpretation. Additionally, geophysicists may rely on dynamic data such as pressure, production rates, saturation, temperature, and fluid properties whenever available. The pressure transient analysis obtained from well tests brings deeper reservoir insights. Estimations of the permeability profile, flow barrier character, and hydraulic compartmentation are some of the possible outcomes. Although the seismic signal and well test have different responses from the reservoir behavior, both can be combined to reduce the ambiguity in seismic interpretation and to evaluate different reservoir scenarios. Assessments among different facies and pore-volume scenarios are also compatible with the dynamic and static data. Turbidite and presalt reservoirs are presented as evidence of how joining geophysical, geologic, and reservoir engineering information, from static and dynamic sources, reduces the risk in quantitative seismic interpretation, thereby leading to more reliable reservoir production forecasting.
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