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AAPG Bulletin, Preliminary version published online Ahead of Print 1 August 2023.

Copyright © 2023. The American Association of Petroleum Geologists. All rights reserved.


Impacts of diagenetic processes on petrophysical characteristics of the Aptian Pre-Salt carbonates of the Santos Basin, Brazil

Hugo Tamoto1* , André Luiz Silva Pestilho2 , and Anelize Manuela Bahniuk Rumbelsperger3

1 Federal University of Paraná (UFPR). Rua Dr. Faivre, 405 - Ed. Dom Pedro II, 1º andar, Centro, 80060-140. Curitiba, Paraná, Brazil
2 University of São Paulo. Institute of Geosciences. Rua do Lago, 562, Cidade Universitária, 05508-080, São Paulo, Brazil
3 Federal University of Paraná (UFPR). LAMIR, Rua Francisco, H. dos Santos, 100. Jardim das Américas. Centro Politécnico. 81531-980. Curitiba, Paraná, Brazil
* Corresponding Author

Ahead of Print Abstract

The Pre-Salt carbonate reservoirs located at the marginal basins of Brazil are one the most important hydrocarbon provinces worldwide. These reservoirs are responsible for approximately 75% of the Brazilian offshore oil production. Despite Pre-Salt reservoirs present good petrophysical qualities (porosity > 15% and permeability > 100mD), there are still challenges related to the lack of understanding on the petrophysical controls resulting from a complex depositional and diagenetic history. To address such problems, an overall evaluation of the carbonate reservoir was provided on the Aptian Barra Velha Formation in the Sapinhoá field, Santos Basin. This research used an extensive dataset of well-logs, petrophysics, and X-ray diffraction, which identified facies heterogeneities, variated petrophysical distribution, and 5 hydraulic flow units. Overall, the best petrophysical intervals with highest porosity and permeability are found in the wells located at the structural high, comprising the flow units 4-5, and mostly consisted of Shrub and Grain-supported facies; followed by an intermediary flow unit 3 found in all wells. Moreover, among all units, flow units 1-2 presented lowest petrophysical values, mainly found at the basinward wells. Finally, results indicate that key diagenetic features such as: dissolution of clay minerals, dissolution of calcite fabric, and dolomitization processes are notable elements that commonly enhanced petrophysical properties. Additionally, the pervasive silicification process decrease the reservoir quality. These processes are often found in the wells located in structural high and basinward area of the field. Lastly, a multiscale characterization allows a broad comprehension of the key diagenetic impacts into carbonate’s petrophysical properties.

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Please cite this AAPG Bulletin Ahead of Print article as:

Hugo Tamoto , André Luiz Silva Pestilho , Anelize Manuela Bahniuk Rumbelsperger: Impacts of diagenetic processes on petrophysical characteristics of the Aptian Pre-Salt carbonates of the Santos Basin, Brazil, (in press; preliminary version published online Ahead of Print 01 August 2023: AAPG Bulletin, DOI:10.1306/05302322046.