Facies Grouping of the Barra Velha Formation in the Santos Basin Using Genetic Criteria
Event - Medterranean Geosciences Union 5th Annual Meeting
Abstract
The Barra Velha Formation is a Cretaceous stratigraphic unit in the Santos Basin, Tupi Field, Brazil. It contains unique carbonate and non-carbonate rocks that do not fit classical carbonate classification systems. This work proposes a facies grouping into three categories based on genetic criteria. The protocol aims to (1) organize groups defined by vertical facies stacking profiles and their heterogeneities, (2) support the definition of facies associa-tions and the interpretation of depositional processes and systems, and (3) better understand heterogeneities that control reservoir rock quality. The method included a sedimentological description of drill cores from Tupi Field wells. Petrographic microscopy was performed on thin sections prepa-red from core plugs and sidewall core samples. The autochthonous facies include crustiform limestones (shrubby and pseudo-peloidal), laminated cal-cilutite, and Si-Mg silicate-rich argillites. The allochthonous facies include unique clastic rocks. The grains consist primarily of carbonate constituents of the Barra Velha Formation itself. Secondarily, they contain fragments of volcanic rocks, bioclastic calcirudites and calcarenites and silexites. The dia-genetic facies include nodular limestones (mainly shrubby, spherulic, and peloidal calcite nodules), dolomites, and silexites. The three groups highlight the importance of sedimentary facies genesis. This helps define facies associ-ations, vertical stacking organization, inter-well stratigraphic correlations, interpretation of depositional processes and systems, integrated studies at different scales, and studies focused on reservoir rock quality. This work proposes a method with potential for direct application in prospective and reservoir development research, aiming to reduce exploration uncertainties and optimize resource utilization, favoring more responsible consumption and production practices, aligned with UN Sustainable Development Goal (SDG) 12.
