Aptian siliciclastic onshore deposits of the Mucuri Member are important reservoirs in the Espíri... more Aptian siliciclastic onshore deposits of the Mucuri Member are important reservoirs in the Espírito Santo Basin (eastern Brazil). A detailed quantitative petrographical and textural analysis of well core samples was performed in order to unravel their depositional processes and conditions, in relation to previously proposed depositional models. The results allowed differentiation between two groups of sandstone samples, characterized by different textural characteristics associated to different depositional processes and environments within the Mucuri depositional system. Fluvial sandstones are represented by medium- to coarse-grained, poorly sorted arkoses, rich in plutonic rock fragments and feldspar grains, mainly transported by traction. Coastal-lacustrine sandstones correspond to very fine- to fine-grained, moderately sorted micaceous arkoses, mainly transported in suspension. The application of a discriminant function based on grain-size parameters validated previously propose...
Second EAGE Conference on Pre-Salt Reservoir, 2021
Summary The Pre-salt reservoirs of the sag section from the Santos and Campos basins are the prod... more Summary The Pre-salt reservoirs of the sag section from the Santos and Campos basins are the product of a vast lacustrine system, formed during the early South Atlantic opening. The in situ deposits were formed by the syngenetic deposition of stevensite and similar magnesian phyllosilicates, which were replaced, displaced and covered by calcite spherulites and fascicular shrubs during early diagenesis. Frequent, high-frequency compositional changes, which may have been related to lake waters stratification, promoted the alternation of levels with predominance of calcite shrubs, spherulites, or of stevensite matrix, as well as its early diagenetic dissolution and replacement by silica, dolomite, magnesite or calcite. The flow of burial diagenetic and hydrothermal fluids through porous layers, faults and fracture zones caused the precipitation of quartz, chalcedony, dolomite, calcite, barite/celestite, pyrite and other sulphides in some areas, but also significant dissolution and porosity enhancement, responsible for the exceptional performance of some reservoirs. Although for the recent advances in the understanding of the origin and evolution of the South Atlantic Pre-salt reservoirs, the sources for the huge volume of Ca, Mg and Si precipitated in the Pre-salt sag succession, remain to the determined.
The forearc succession of Great Valley Group in Central California provides some of the best exam... more The forearc succession of Great Valley Group in Central California provides some of the best examples of giant sand injection complexes in the world and is therefore considered valuable analogues for injectite systems in subsurface. Several sand injection complexes are well described in the outcrop and subsurface, however the petrographic characteristics of injectites are still poorly documented. In this paper, we present the results of an integrated study of field observations, quantitative and qualitative sandstone petrography, provenance, and petrofacies analysis of the Tumey Giant Injection Complex (TGIC) in order to understand its lithostratigraphy and petrological evolution, and its impacts on reservoir petrofacies characteristics and fluid migration. The TGIC intrudes into a 450 m thick deep-water succession of slope mudrocks and sandy channel-fills of the Kreyenhagen Shale Eocene), forming an interconnected network of sandstone sills, dykes and injection breccias. The complex generated a horizontal and vertical plumbing system for fluid migration, connecting isolated sandy channel-fills 2 among low-permeability mudrocks. The primary detrital composition, diagenetic products, microtextures, and provenance signatures allowed for the definition and discrimination of depositional and intrusive petrofacies and their genetic relations. Petrofacies associations confirm that the gypsum-cemented feldspathic litharenites from the Kreyenhagen Shale channel-fills are the only source for the injection complex. Eodiagenetic compaction and extensive gypsum cementation reduced the primary porosity of the complex, while telodiagenetic dissolution of autigenic constituents formed pervasive secondary porosity. The underlying calcite-cemented arkosic sandstones of the Lodo and Domengine formations acted as barriers for fluid flow, aiding lateral fluid migration and overpressure buildup within the overlying Kreyenhagen channel-fills. Intense grain microfracturing occurred during sand remobilization and injection along with erosion of the host mudrocks. This study has significance for the generation of reliable stratigraphic and petrological models for sand injection complex genesis and evolution that consequently can help the understanding and exploration of injectite complexes elsewhere.
A new petrographical study was performed on the rift section of the Lagoa Feia Group, Lower Creta... more A new petrographical study was performed on the rift section of the Lagoa Feia Group, Lower Cretaceous of the Campos Basin, eastern Brazilian margin. The primary constituents of the analysed rocks are siliciclastic and volcaniclastic grains, stevensite ooids and peloids, and bioclasts of bivalves and ostracods. This study focused on the clastic, stevensitic and hybrid rocks, as previous studies were limited to the bioclastic rudstones and grainstones that constitute the producing reservoirs. The rift sedimentation was mostly intrabasinal, with extrabasinal contribution concentrated close to half-graben border faults. The mixture of rounded volcanic fragments with angular quartz, feldspars and plutonic fragments in the sandstones and conglomerates indicates recycling of early rift epiclastic deposits, combined with first-cycle sediments eroded from uplifted plutonic basement blocks. Stevensitic ooids and peloids, formed in shallow, alkaline lacustrine environments, were mixed throughout the rift section with bivalve and ostracod bioclasts, and with the clastic sediments. Gravitational redeposition was promoted by intense and recurrent tectonism along the rift margins. The main diagenetic processes in clastic sandstones and conglomerates and hybrid arenites are cementation and grain replacement by smectite, zeolites, calcite and dolomite, mechanical compaction and dissolution of feldspars, volcanic fragments and bioclasts. Stevensitic arenites experienced early cementation and replacement of ooids and peloids by quartz, calcite and dolomite, or intense compaction of stevensitic grains in uncemented areas. Volcaniclastic sandstones and conglomerates with smectite rims, remnant intergranular porosity and grain dissolution may constitute fair hydrocarbon reservoirs. Stevensitic and hybrid arenites with dissolution of stevensite grains, bioclasts and calcite cement may also constitute reservoirs, although with potential quality limited by the poor connection of their pore systems. An understanding of the controls on the depositional and diagenetic evolution of the dominantly intrabasinal, gravitationally redeposited, rift succession will contribute to new exploration strategies for the Campos Basin.
Carbonate diagenesis and porosity evolution in sheet flood sandstones: evidence from the Lunde me... more Carbonate diagenesis and porosity evolution in sheet flood sandstones: evidence from the Lunde members (Triassic) in the Snorre oilfield, Norwegian North Sea
Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservo... more Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservoir sandstones: evidence from the Early Cretaceous Serraria Sandstones in the Sergipe-Alagoas Basin, NE Brazil
The role of the Cimmerian Unconformity on the reservoir quality evolution of sandstones: evidence... more The role of the Cimmerian Unconformity on the reservoir quality evolution of sandstones: evidence from the Triassic Lunde Formation, the Snorre Field, northern North Sea.
Despite a great interest in Brazilian Equatorial Margin exploration, very little was published on... more Despite a great interest in Brazilian Equatorial Margin exploration, very little was published on the diagenesis of sandstones from that area. A wide recognition petrographic study was performed to identify the major diagenetic processes that impacted the porosity of Lower Cretaceous sandstones of the Par a-Maranhão, São Luís, Bragança-Viseu and Barreirinhas basins. Arkoses from the Par a-Maranhão Basin show neoformed or infiltrated clay coatings, mica replacement and expansion by kaolinite and vermiculite, and precipitation of grain-replacive and pore-filling quartz, kaolinite, albite, chlorite, calcite, dolomite, siderite, pyrite and titanium oxides. Compaction, quartz and calcite cementation were the main porosity-reducing processes. Barreirinhas Basin lithic arkoses and subarkoses display clay coatings, compaction of metamorphic fragments into pseudomatrix, and precipitation of grain-replacive and porefilling kaolinite, quartz, albite, chlorite, calcite, dolomite, TiO 2 and pyrite. The main porosity-reducing processes were calcite cementation in the subarkoses, and compaction and quartz cementation in lithic arkoses. Quartzarenites from this basin were early-and pervasively cemented by dolomite. Arkoses and lithic arkoses of the São Luís and Bragança-Viseu basins show clay coatings, pseudomatrix from mud intraclasts compaction, and precipitation of pore-filling and grain-replacive kaolinite, vermiculite, smectite, quartz, albite, chlorite, illite, calcite, dolomite, hematite, TiO 2 and pyrite. Compaction of mud intraclasts and dissolution of feldspars and heavy minerals were the main porosity-modification processes. These preliminary results may contribute to the understanding of the spatial and temporal distribution of the diagenetic processes and their impacts on the porosity of the sandstones from these basins.
This is an open access article under the terms of the Creat ive Commo ns Attri bution License, wh... more This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a... more A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a se abrir, durante o Paleoceno. Há referências à existência de calcretes na bacia, entretanto, até o momento, não foram realizados estudos específicos sobre os calcretes e sobre sua ocorrência, e ainda há um número reduzido de trabalhos envolvendo a caracterização petrográfica dos depósitos sedimentares da bacia. Apresenta-se aqui uma caracterização, macromorfológica e micromorfológica dos calcretes vadosos que constituem o preenchimento inicial da bacia e que são encontrados nas suas bordas norte e oeste. Foram descritos e interpretados os aspectos composicionais, texturais e de fábrica de 27 seções delgadas preparadas de amostras de calcretes. Os calcretes pedogenéticos mostram diferentes fácies (pulverulento, nodular, maciço, placoso, laminar incipiente e brechado), que foram atribuídas a estágios morfogenéticos distintos. As principais fei- ções micromorfológicas incluem: nódulos, gr...
A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a... more A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a se abrir, durante o Paleoceno. Há referências à existência de calcretes na bacia, entretanto, até o momento, não foram realizados estudos específicos sobre os calcretes e sobre sua ocorrência, e ainda há um número reduzido de trabalhos envolvendo a caracterização petrográfica dos depósitos sedimentares da bacia. Apresenta-se aqui uma caracterização, macromorfológica e micromorfológica dos calcretes vadosos que constituem o preenchimento inicial da bacia e que são encontrados nas suas bordas norte e oeste. Foram descritos e interpretados os aspectos composicionais, texturais e de fábrica de 27 seções delgadas preparadas de amostras de calcretes. Os calcretes pedogenéticos mostram diferentes fácies (pulverulento, nodular, maciço, placoso, laminar incipiente e brechado), que foram atribuídas a estágios morfogenéticos distintos. As principais fei- ções micromorfológicas incluem: nódulos, gr...
The Cretaceous fluvial sandstones of the Açu Formation, Potiguar Basin, northeastern Brazil, cont... more The Cretaceous fluvial sandstones of the Açu Formation, Potiguar Basin, northeastern Brazil, contain abundant, very early, authigenic K‐feldspar overgrowths around detrital orthoclase and microcline grains. Detailed optical and cathodoluminescence petrography, scanning ...
Resumo - Arenitos devonianos marinhos rasos da Formação Uerê são impotantes prospectos de óleo na... more Resumo - Arenitos devonianos marinhos rasos da Formação Uerê são impotantes prospectos de óleo na Bacia do Solimões, Amazônia ocidental.Os reservatórios são arenitos progradacionais com contatos basais abruptos, depositados em um complexo de plataforma dominado por tempestades, e recobertos por folhelhos pretos de Frasniano- Fameniano que são as rochas geradoras de petróleo da bacia. Concentrações de espículas de esponjas ocorrem intercaladas com os arenitos, como restos de esponjas individuais ou coloniais, recristalizadas a nódulos, lentes e camadas de chert. Apesar de sua grande extensão lateral, a exploração desses arenitos é dificultada pelos intensos e heterogêneous procesos diagenéticos que fortemente afetaram a qualidade dos reservatórios. A porosidade dos arenitos varia de extremamente fechada (menos de 5 %), a valores anormalmente altos (até 28 %), considerando-se a longa e complexa história de soterramen to dos reservatórios. Os principais processos de redução da porosida...
Resumo: Ontologias de domínio mostram-se abordagens poderosas para a captura do conhecimento estr... more Resumo: Ontologias de domínio mostram-se abordagens poderosas para a captura do conhecimento estratégico e tem sido grandemente estudadas no domínio da Geologia de Petróleo. Geólogos aplicam múltiplas formas de conhecimento na solução de problemas, dos quais o conhecimento visual mostrase o mais importante nas tarefas de interpretação, porém é de difícil captura pelos construtos ontológicos existentes. Propomos neste trabalho a definição de primitivas de representação de conhecimento visual em três níveis de abstração, mantendo o ancoramento simbólico dos conceitos entre os níveis. Propomos ainda primitivas para a construção de ontologias temporais para a identificação de seqüências de eventos sem rótulo de tempo. Os resultados deste projeto foram implementados em um sistema para descrição petrográfica e análise de qualidade de rochasreservatórios Palavras-chave: Ontologias para conhecimento visual, ontologia de eventos, Geologia de Petróleo
Silurian-Devonian sandstones of the Fumas Formation in the intracratonic Paran Basin, southern Br... more Silurian-Devonian sandstones of the Fumas Formation in the intracratonic Paran Basin, southern Brazil, display strongly heterogeneous distribution of quartz, kaolinite and illite authigenesis. The sandstones were affected by extensive dissolution/kaolinization of detrital feldspar, mica and clay under an eodiagenetic meteoric regime. Circulation of hot fluids through fractures related to the uplift and magmatism along the regional Ponta Grossa Arch promoted heterogeneous kaolinite and feldspar illitization and quartz cementation. This is supported by intense illitization of kaolinite at shallow depths, by WAr dating of the illite, whose age coincides with the magmatism, and by high fluid inclusion homogenization temperatures in quartz overgrowths from outcrop-samples. The progressive destruction of feldspar generated diagenetic quartzarenites with poorly connected pore systems and low reservoir potential. Evidence yielded by this study suggests that the application of simplified 'isochemical' models of diagenetic processes within the system Si02-A1203-K1O-Hz0 may have very limited validity, applying basically to the deep-burial mesodiagenesis of some sandstones in rapidly subsiding basins.
Aptian siliciclastic onshore deposits of the Mucuri Member are important reservoirs in the Espíri... more Aptian siliciclastic onshore deposits of the Mucuri Member are important reservoirs in the Espírito Santo Basin (eastern Brazil). A detailed quantitative petrographical and textural analysis of well core samples was performed in order to unravel their depositional processes and conditions, in relation to previously proposed depositional models. The results allowed differentiation between two groups of sandstone samples, characterized by different textural characteristics associated to different depositional processes and environments within the Mucuri depositional system. Fluvial sandstones are represented by medium- to coarse-grained, poorly sorted arkoses, rich in plutonic rock fragments and feldspar grains, mainly transported by traction. Coastal-lacustrine sandstones correspond to very fine- to fine-grained, moderately sorted micaceous arkoses, mainly transported in suspension. The application of a discriminant function based on grain-size parameters validated previously propose...
Second EAGE Conference on Pre-Salt Reservoir, 2021
Summary The Pre-salt reservoirs of the sag section from the Santos and Campos basins are the prod... more Summary The Pre-salt reservoirs of the sag section from the Santos and Campos basins are the product of a vast lacustrine system, formed during the early South Atlantic opening. The in situ deposits were formed by the syngenetic deposition of stevensite and similar magnesian phyllosilicates, which were replaced, displaced and covered by calcite spherulites and fascicular shrubs during early diagenesis. Frequent, high-frequency compositional changes, which may have been related to lake waters stratification, promoted the alternation of levels with predominance of calcite shrubs, spherulites, or of stevensite matrix, as well as its early diagenetic dissolution and replacement by silica, dolomite, magnesite or calcite. The flow of burial diagenetic and hydrothermal fluids through porous layers, faults and fracture zones caused the precipitation of quartz, chalcedony, dolomite, calcite, barite/celestite, pyrite and other sulphides in some areas, but also significant dissolution and porosity enhancement, responsible for the exceptional performance of some reservoirs. Although for the recent advances in the understanding of the origin and evolution of the South Atlantic Pre-salt reservoirs, the sources for the huge volume of Ca, Mg and Si precipitated in the Pre-salt sag succession, remain to the determined.
The forearc succession of Great Valley Group in Central California provides some of the best exam... more The forearc succession of Great Valley Group in Central California provides some of the best examples of giant sand injection complexes in the world and is therefore considered valuable analogues for injectite systems in subsurface. Several sand injection complexes are well described in the outcrop and subsurface, however the petrographic characteristics of injectites are still poorly documented. In this paper, we present the results of an integrated study of field observations, quantitative and qualitative sandstone petrography, provenance, and petrofacies analysis of the Tumey Giant Injection Complex (TGIC) in order to understand its lithostratigraphy and petrological evolution, and its impacts on reservoir petrofacies characteristics and fluid migration. The TGIC intrudes into a 450 m thick deep-water succession of slope mudrocks and sandy channel-fills of the Kreyenhagen Shale Eocene), forming an interconnected network of sandstone sills, dykes and injection breccias. The complex generated a horizontal and vertical plumbing system for fluid migration, connecting isolated sandy channel-fills 2 among low-permeability mudrocks. The primary detrital composition, diagenetic products, microtextures, and provenance signatures allowed for the definition and discrimination of depositional and intrusive petrofacies and their genetic relations. Petrofacies associations confirm that the gypsum-cemented feldspathic litharenites from the Kreyenhagen Shale channel-fills are the only source for the injection complex. Eodiagenetic compaction and extensive gypsum cementation reduced the primary porosity of the complex, while telodiagenetic dissolution of autigenic constituents formed pervasive secondary porosity. The underlying calcite-cemented arkosic sandstones of the Lodo and Domengine formations acted as barriers for fluid flow, aiding lateral fluid migration and overpressure buildup within the overlying Kreyenhagen channel-fills. Intense grain microfracturing occurred during sand remobilization and injection along with erosion of the host mudrocks. This study has significance for the generation of reliable stratigraphic and petrological models for sand injection complex genesis and evolution that consequently can help the understanding and exploration of injectite complexes elsewhere.
A new petrographical study was performed on the rift section of the Lagoa Feia Group, Lower Creta... more A new petrographical study was performed on the rift section of the Lagoa Feia Group, Lower Cretaceous of the Campos Basin, eastern Brazilian margin. The primary constituents of the analysed rocks are siliciclastic and volcaniclastic grains, stevensite ooids and peloids, and bioclasts of bivalves and ostracods. This study focused on the clastic, stevensitic and hybrid rocks, as previous studies were limited to the bioclastic rudstones and grainstones that constitute the producing reservoirs. The rift sedimentation was mostly intrabasinal, with extrabasinal contribution concentrated close to half-graben border faults. The mixture of rounded volcanic fragments with angular quartz, feldspars and plutonic fragments in the sandstones and conglomerates indicates recycling of early rift epiclastic deposits, combined with first-cycle sediments eroded from uplifted plutonic basement blocks. Stevensitic ooids and peloids, formed in shallow, alkaline lacustrine environments, were mixed throughout the rift section with bivalve and ostracod bioclasts, and with the clastic sediments. Gravitational redeposition was promoted by intense and recurrent tectonism along the rift margins. The main diagenetic processes in clastic sandstones and conglomerates and hybrid arenites are cementation and grain replacement by smectite, zeolites, calcite and dolomite, mechanical compaction and dissolution of feldspars, volcanic fragments and bioclasts. Stevensitic arenites experienced early cementation and replacement of ooids and peloids by quartz, calcite and dolomite, or intense compaction of stevensitic grains in uncemented areas. Volcaniclastic sandstones and conglomerates with smectite rims, remnant intergranular porosity and grain dissolution may constitute fair hydrocarbon reservoirs. Stevensitic and hybrid arenites with dissolution of stevensite grains, bioclasts and calcite cement may also constitute reservoirs, although with potential quality limited by the poor connection of their pore systems. An understanding of the controls on the depositional and diagenetic evolution of the dominantly intrabasinal, gravitationally redeposited, rift succession will contribute to new exploration strategies for the Campos Basin.
Carbonate diagenesis and porosity evolution in sheet flood sandstones: evidence from the Lunde me... more Carbonate diagenesis and porosity evolution in sheet flood sandstones: evidence from the Lunde members (Triassic) in the Snorre oilfield, Norwegian North Sea
Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservo... more Paleoclimatic, paleogeographic and burial-history controls on the diagenetic evolution of reservoir sandstones: evidence from the Early Cretaceous Serraria Sandstones in the Sergipe-Alagoas Basin, NE Brazil
The role of the Cimmerian Unconformity on the reservoir quality evolution of sandstones: evidence... more The role of the Cimmerian Unconformity on the reservoir quality evolution of sandstones: evidence from the Triassic Lunde Formation, the Snorre Field, northern North Sea.
Despite a great interest in Brazilian Equatorial Margin exploration, very little was published on... more Despite a great interest in Brazilian Equatorial Margin exploration, very little was published on the diagenesis of sandstones from that area. A wide recognition petrographic study was performed to identify the major diagenetic processes that impacted the porosity of Lower Cretaceous sandstones of the Par a-Maranhão, São Luís, Bragança-Viseu and Barreirinhas basins. Arkoses from the Par a-Maranhão Basin show neoformed or infiltrated clay coatings, mica replacement and expansion by kaolinite and vermiculite, and precipitation of grain-replacive and pore-filling quartz, kaolinite, albite, chlorite, calcite, dolomite, siderite, pyrite and titanium oxides. Compaction, quartz and calcite cementation were the main porosity-reducing processes. Barreirinhas Basin lithic arkoses and subarkoses display clay coatings, compaction of metamorphic fragments into pseudomatrix, and precipitation of grain-replacive and porefilling kaolinite, quartz, albite, chlorite, calcite, dolomite, TiO 2 and pyrite. The main porosity-reducing processes were calcite cementation in the subarkoses, and compaction and quartz cementation in lithic arkoses. Quartzarenites from this basin were early-and pervasively cemented by dolomite. Arkoses and lithic arkoses of the São Luís and Bragança-Viseu basins show clay coatings, pseudomatrix from mud intraclasts compaction, and precipitation of pore-filling and grain-replacive kaolinite, vermiculite, smectite, quartz, albite, chlorite, illite, calcite, dolomite, hematite, TiO 2 and pyrite. Compaction of mud intraclasts and dissolution of feldspars and heavy minerals were the main porosity-modification processes. These preliminary results may contribute to the understanding of the spatial and temporal distribution of the diagenetic processes and their impacts on the porosity of the sandstones from these basins.
This is an open access article under the terms of the Creat ive Commo ns Attri bution License, wh... more This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a... more A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a se abrir, durante o Paleoceno. Há referências à existência de calcretes na bacia, entretanto, até o momento, não foram realizados estudos específicos sobre os calcretes e sobre sua ocorrência, e ainda há um número reduzido de trabalhos envolvendo a caracterização petrográfica dos depósitos sedimentares da bacia. Apresenta-se aqui uma caracterização, macromorfológica e micromorfológica dos calcretes vadosos que constituem o preenchimento inicial da bacia e que são encontrados nas suas bordas norte e oeste. Foram descritos e interpretados os aspectos composicionais, texturais e de fábrica de 27 seções delgadas preparadas de amostras de calcretes. Os calcretes pedogenéticos mostram diferentes fácies (pulverulento, nodular, maciço, placoso, laminar incipiente e brechado), que foram atribuídas a estágios morfogenéticos distintos. As principais fei- ções micromorfológicas incluem: nódulos, gr...
A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a... more A Bacia de Itaboraí é considerada o primeiro segmento do Rifte Continental do Sudeste do Brasil a se abrir, durante o Paleoceno. Há referências à existência de calcretes na bacia, entretanto, até o momento, não foram realizados estudos específicos sobre os calcretes e sobre sua ocorrência, e ainda há um número reduzido de trabalhos envolvendo a caracterização petrográfica dos depósitos sedimentares da bacia. Apresenta-se aqui uma caracterização, macromorfológica e micromorfológica dos calcretes vadosos que constituem o preenchimento inicial da bacia e que são encontrados nas suas bordas norte e oeste. Foram descritos e interpretados os aspectos composicionais, texturais e de fábrica de 27 seções delgadas preparadas de amostras de calcretes. Os calcretes pedogenéticos mostram diferentes fácies (pulverulento, nodular, maciço, placoso, laminar incipiente e brechado), que foram atribuídas a estágios morfogenéticos distintos. As principais fei- ções micromorfológicas incluem: nódulos, gr...
The Cretaceous fluvial sandstones of the Açu Formation, Potiguar Basin, northeastern Brazil, cont... more The Cretaceous fluvial sandstones of the Açu Formation, Potiguar Basin, northeastern Brazil, contain abundant, very early, authigenic K‐feldspar overgrowths around detrital orthoclase and microcline grains. Detailed optical and cathodoluminescence petrography, scanning ...
Resumo - Arenitos devonianos marinhos rasos da Formação Uerê são impotantes prospectos de óleo na... more Resumo - Arenitos devonianos marinhos rasos da Formação Uerê são impotantes prospectos de óleo na Bacia do Solimões, Amazônia ocidental.Os reservatórios são arenitos progradacionais com contatos basais abruptos, depositados em um complexo de plataforma dominado por tempestades, e recobertos por folhelhos pretos de Frasniano- Fameniano que são as rochas geradoras de petróleo da bacia. Concentrações de espículas de esponjas ocorrem intercaladas com os arenitos, como restos de esponjas individuais ou coloniais, recristalizadas a nódulos, lentes e camadas de chert. Apesar de sua grande extensão lateral, a exploração desses arenitos é dificultada pelos intensos e heterogêneous procesos diagenéticos que fortemente afetaram a qualidade dos reservatórios. A porosidade dos arenitos varia de extremamente fechada (menos de 5 %), a valores anormalmente altos (até 28 %), considerando-se a longa e complexa história de soterramen to dos reservatórios. Os principais processos de redução da porosida...
Resumo: Ontologias de domínio mostram-se abordagens poderosas para a captura do conhecimento estr... more Resumo: Ontologias de domínio mostram-se abordagens poderosas para a captura do conhecimento estratégico e tem sido grandemente estudadas no domínio da Geologia de Petróleo. Geólogos aplicam múltiplas formas de conhecimento na solução de problemas, dos quais o conhecimento visual mostrase o mais importante nas tarefas de interpretação, porém é de difícil captura pelos construtos ontológicos existentes. Propomos neste trabalho a definição de primitivas de representação de conhecimento visual em três níveis de abstração, mantendo o ancoramento simbólico dos conceitos entre os níveis. Propomos ainda primitivas para a construção de ontologias temporais para a identificação de seqüências de eventos sem rótulo de tempo. Os resultados deste projeto foram implementados em um sistema para descrição petrográfica e análise de qualidade de rochasreservatórios Palavras-chave: Ontologias para conhecimento visual, ontologia de eventos, Geologia de Petróleo
Silurian-Devonian sandstones of the Fumas Formation in the intracratonic Paran Basin, southern Br... more Silurian-Devonian sandstones of the Fumas Formation in the intracratonic Paran Basin, southern Brazil, display strongly heterogeneous distribution of quartz, kaolinite and illite authigenesis. The sandstones were affected by extensive dissolution/kaolinization of detrital feldspar, mica and clay under an eodiagenetic meteoric regime. Circulation of hot fluids through fractures related to the uplift and magmatism along the regional Ponta Grossa Arch promoted heterogeneous kaolinite and feldspar illitization and quartz cementation. This is supported by intense illitization of kaolinite at shallow depths, by WAr dating of the illite, whose age coincides with the magmatism, and by high fluid inclusion homogenization temperatures in quartz overgrowths from outcrop-samples. The progressive destruction of feldspar generated diagenetic quartzarenites with poorly connected pore systems and low reservoir potential. Evidence yielded by this study suggests that the application of simplified 'isochemical' models of diagenetic processes within the system Si02-A1203-K1O-Hz0 may have very limited validity, applying basically to the deep-burial mesodiagenesis of some sandstones in rapidly subsiding basins.
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