Salt Heterogeneities Characterization in Pre-Salt Santos Basin Fields

Abstract

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.

Deformation of intrasalt competent layers in different modes of salt tectonics

“…Neither of these is likely to be correct. Even approaches that combine seismic images with lithology and velocity data calibrated from wells (e.g., Barros et al, 2017) are liable to be inaccurate because the transparent areas typically include stringers of non-halite lithologies that are not imaged. In other words, the transparent and layered areas usually have less and more halite, respectively, than thought.…”

Geological Characterization of Evaporitic Sections and Its Impacts on Seismic Images: Santos Basin, Offshore Brazil

“…Notice that well D, for example, does not contain any LVS interpreted in neither approach. Barros et al (2017) proposed to use constant values (average logged values) for each of the mineral groups, in order to fill the gaps in the logs -i.e., assuming generated pseudo-logs as hard information. To do so, we will use the following average values: LVS = 4,188 m/s; Halite = 4,548 m/s; and HVS = 5,281.…”

“…Several other authors have explored the adaptive inversion concepts from the reservoir scale to the salt section scale (Gobatto et al, 2016;Toríbio et al, 2017;Teixeira et al, 2018;Fonseca et al, 2018). Barros et al (2017) introduced the idea of generating pseudo-logs to fill log gaps, using the approach stablished by Amaral et al (2015), who relied on cutting samples (mud-logs) collected during the well drilling phase. The use of mud-logs was also demonstrated to be useful in the work published by Cornelius & Castagna (2018).…”

Improving Pre-Salt Reservoirs Seismic Images When Considering the Stratified Evaporites Insertion in the Initial Model for the Velocity Updating Processes Prior to the Seismic Migration

“…7C). The importance of considering the model-based inversion approach to better establish the stratification is well exemplified and documented in several works (Meneguim et al, 2015;Teixeira et al, 2017;Toríbio et al, 2017;Barros et al, 2017Teixeira et al, 2018;Maul et al, 2019aMaul et al, , 2019bTeixeira & Lupinacci, 2019).…”