Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin
The giant Pre-salt reservoirs represent most of the oil production in Brazil. The main Aptian sag reservoirs were deposited in a unique and highly complex hyper-alkaline lacustrine setting. These deposits are essentially constituted by fascicular and spherulitic calcite precipitated in a magnesian c...
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| Format: | Article |
| Language: | English |
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MDPI AG
2024-02-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/14/2/191 |
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| author | Argos Belmonte Silveira Schrank Thisiane Dos Santos Sabrina Danni Altenhofen William Freitas Elias Cembrani Thiago Haubert Felipe Dalla Vecchia Rosalia Barili Amanda Goulart Rodrigues Anderson Maraschin Luiz Fernando De Ros |
| author_facet | Argos Belmonte Silveira Schrank Thisiane Dos Santos Sabrina Danni Altenhofen William Freitas Elias Cembrani Thiago Haubert Felipe Dalla Vecchia Rosalia Barili Amanda Goulart Rodrigues Anderson Maraschin Luiz Fernando De Ros |
| author_sort | Argos Belmonte Silveira Schrank |
| collection | DOAJ |
| description | The giant Pre-salt reservoirs represent most of the oil production in Brazil. The main Aptian sag reservoirs were deposited in a unique and highly complex hyper-alkaline lacustrine setting. These deposits are essentially constituted by fascicular and spherulitic calcite precipitated in a magnesian clay matrix (stevensite, kerolite, and saponite/hectorite). Although vital for understanding the origin and main reservoir quality control, the genesis and interactions of clays and carbonates are still poorly constrained. The detailed petrographic description was focused on 812 thin sections from five wells drilled in the Santos Basin Aptian Barra Velha Formation, combined with cathodoluminescence, UV epifluorescence, and X-ray diffraction analyses. The main syngenetic processes were the deposition of finely laminated peloidal and ooidal Mg-clays, the formation of fascicular calcite crusts on the sediment–water interface, and the redeposition of these materials as intraclasts. Abundant clay peloids engulfed in syngenetic shrubs indicate that calcite and clay precipitation was concomitant, though with highly variable rates. Eodiagenetic phases include matrix-replacive and -displacive spherulites and fascicular shrubs; matrix-replacive blocky calcite and dolomite; lamellar carbonates filling matrix shrinkage pores; and microcrystalline calcite, dolomite, and silica replacing the Mg-clay matrix. The preferential dolomitization and calcitization of peloidal layers were most likely due to their higher permeability and larger specific surface. Matrix-replacive saddle dolomite, macrocrystalline calcite, and dawsonite are interpreted as mesodiagenetic or hydrothermal phases after significant matrix dissolution. Unraveling the processes of the formation and alteration of the carbonates and clays and their interactions in the Pre-salt deposits is essential for constraining the depositional and diagenetic conditions in their unique environments and their diagenetic overprinting and for decreasing the exploration risks and increasing the production of those extraordinary reservoirs. |
| first_indexed | 2024-03-07T22:19:50Z |
| format | Article |
| id | doaj.art-6a3d64cb9349455dae9ef6f00860bad0 |
| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-07T22:19:50Z |
| publishDate | 2024-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-6a3d64cb9349455dae9ef6f00860bad02024-02-23T15:28:42ZengMDPI AGMinerals2075-163X2024-02-0114219110.3390/min14020191Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian MarginArgos Belmonte Silveira Schrank0Thisiane Dos Santos1Sabrina Danni Altenhofen2William Freitas3Elias Cembrani4Thiago Haubert5Felipe Dalla Vecchia6Rosalia Barili7Amanda Goulart Rodrigues8Anderson Maraschin9Luiz Fernando De Ros10Instituto de Geociências, Campus do Vale. Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500 Agronomia, Porto Alegre 90650-001, BrazilInstitute of Petroleum and Natural Resources (IPR), Building 96J, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6681-Partenon, Porto Alegre 90619-900, BrazilInstitute of Petroleum and Natural Resources (IPR), Building 96J, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6681-Partenon, Porto Alegre 90619-900, BrazilInstitute of Petroleum and Natural Resources (IPR), Building 96J, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6681-Partenon, Porto Alegre 90619-900, BrazilInstituto de Geociências, Campus do Vale. Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500 Agronomia, Porto Alegre 90650-001, BrazilInstitute of Petroleum and Natural Resources (IPR), Building 96J, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6681-Partenon, Porto Alegre 90619-900, BrazilInstitute of Petroleum and Natural Resources (IPR), Building 96J, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6681-Partenon, Porto Alegre 90619-900, BrazilInstitute of Petroleum and Natural Resources (IPR), Building 96J, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6681-Partenon, Porto Alegre 90619-900, BrazilInstituto de Geociências, Campus do Vale. Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500 Agronomia, Porto Alegre 90650-001, BrazilInstitute of Petroleum and Natural Resources (IPR), Building 96J, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga, 6681-Partenon, Porto Alegre 90619-900, BrazilInstituto de Geociências, Campus do Vale. Federal University of Rio Grande do Sul (UFRGS), Av. Bento Gonçalves, 9500 Agronomia, Porto Alegre 90650-001, BrazilThe giant Pre-salt reservoirs represent most of the oil production in Brazil. The main Aptian sag reservoirs were deposited in a unique and highly complex hyper-alkaline lacustrine setting. These deposits are essentially constituted by fascicular and spherulitic calcite precipitated in a magnesian clay matrix (stevensite, kerolite, and saponite/hectorite). Although vital for understanding the origin and main reservoir quality control, the genesis and interactions of clays and carbonates are still poorly constrained. The detailed petrographic description was focused on 812 thin sections from five wells drilled in the Santos Basin Aptian Barra Velha Formation, combined with cathodoluminescence, UV epifluorescence, and X-ray diffraction analyses. The main syngenetic processes were the deposition of finely laminated peloidal and ooidal Mg-clays, the formation of fascicular calcite crusts on the sediment–water interface, and the redeposition of these materials as intraclasts. Abundant clay peloids engulfed in syngenetic shrubs indicate that calcite and clay precipitation was concomitant, though with highly variable rates. Eodiagenetic phases include matrix-replacive and -displacive spherulites and fascicular shrubs; matrix-replacive blocky calcite and dolomite; lamellar carbonates filling matrix shrinkage pores; and microcrystalline calcite, dolomite, and silica replacing the Mg-clay matrix. The preferential dolomitization and calcitization of peloidal layers were most likely due to their higher permeability and larger specific surface. Matrix-replacive saddle dolomite, macrocrystalline calcite, and dawsonite are interpreted as mesodiagenetic or hydrothermal phases after significant matrix dissolution. Unraveling the processes of the formation and alteration of the carbonates and clays and their interactions in the Pre-salt deposits is essential for constraining the depositional and diagenetic conditions in their unique environments and their diagenetic overprinting and for decreasing the exploration risks and increasing the production of those extraordinary reservoirs.https://www.mdpi.com/2075-163X/14/2/191Pre-saltAptiancarbonate–clay interactionsBarra Velha FormationSantos Basindiagenesis |
| spellingShingle | Argos Belmonte Silveira Schrank Thisiane Dos Santos Sabrina Danni Altenhofen William Freitas Elias Cembrani Thiago Haubert Felipe Dalla Vecchia Rosalia Barili Amanda Goulart Rodrigues Anderson Maraschin Luiz Fernando De Ros Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin Minerals Pre-salt Aptian carbonate–clay interactions Barra Velha Formation Santos Basin diagenesis |
| title | Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin |
| title_full | Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin |
| title_fullStr | Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin |
| title_full_unstemmed | Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin |
| title_short | Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin |
| title_sort | interactions between clays and carbonates in the aptian pre salt reservoirs of santos basin eastern brazilian margin |
| topic | Pre-salt Aptian carbonate–clay interactions Barra Velha Formation Santos Basin diagenesis |
| url | https://www.mdpi.com/2075-163X/14/2/191 |
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