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The evaporitic layer represents the seal for the pre-salt reservoirs in the Santos Basin, Brazil. It has significant thickness variations and presents different type of rocks, thus it impose substantial velocity contrasts. Therefore, a more realistic description of the internal velocities for the salt section, taking into account the different mine...
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Context 1
... in the majority of the studied fields within the Santos Basin, we do not have the density log for the entire salt section, even when we have. It is possible to confirm this statement consulting the work presented by Barros et al., 2017 (Figure 2). The salt section commonly presents lacks of log registering for security concerns. ...
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The last works developed by the Petrobras geological modeling group of seismic velocities of reservoir geophysics area shows the importance of incorporation of existing stratifications in the evaporitic section, Ariri Formation, is a key point to improve velocity models of Pre-Salt, projects in the Santos Basin. The presented workflow proposed to g...
Citations
The present study details the seismic characterization of evaporatic saline section above the Pre-Salt reservoirs in Santos Basin, Southeastern Brazilian margin, aiming at improving the seismic velocity models, applying concepts 3D geological property models, and its main practical applications, emphasizing the development of methodologies.
In regions of high geological complexity, such as especially the evaporatic saline section, seismic velocity models influence the main diverse applications in a wide range of routines within the E&P segment of the oil industry.
The results demonstrate the benefits of detailed seismic characterization of the evaporatic saline section to improve seismic illumination studies, aiming at better defining parameters for new acquisitions, enhancing the seismic illumination of the target, and decreasing the effort and complexity during seismic processing. Equally
relevant is the reduction in uncertainties related to the vertical and horizontal positioning of the events, as well as the quality of the seismic signal to be used as a trend parameter, assisting in accurate distribution of reservoir properties. These approaches improve the volumetric field estimates, with significant economic and operational impacts.
During the exploration, development and production phases accurate seismic velocity models provide additional information for geomechanical simulation studies, allowing for better production and/or injection strategies, providing enhancements in management of project risk and economicity. Optimized lithology predictions provide even greater precision for drilling and fluid parameters during well construction, influencing the choice of the most appropriate rig type when drilling new wells. Important information is also derived for deciding the need of special prevention equipment, providing greater security and economicity to the project as a whole. Regarding the seismic migration workflows, even for the seismic velocity models construction and updating for migration purposes, the insertion of salt heterogeneities, or stratifications, has great importance for the most advanced seismic processing techniques available. The velocity models resulted from this detailed characterization require less computational effort during the tomographic inversion updating process.
Updating velocity models using the Full-Waveform Inversion (FWI) technique requires
initial velocity models presenting strong geological significance, and the Reverse Time-
Migration (RTM) technique also requires more detailed, less smoothed, velocity models.The application of the Least-Squares Migration (LSM) technique also benefits
from more detailed velocity models. Even in terms of seismic anisotropy, the importance of these more detailed models of seismic velocities is observed.
