>Magister Scientiae - MSc / The burial history, thermal maturity and petroleum generation history of the F-O Gas Field, Bredasdorp Basin have been studied using 3D basin and petroleum systems modelling approach. The investigated sedimentary basin for this study evolved around mid-late Jurassic to early Cretaceous times when Southern Africa rifted from South America. The F-O field is located 40 km SE of the F-A platform which supplies gas and condensate to the PetroSA ‘Gas to Liquid’ plant located in Mossel Bay. As data integration is an integral part of the applied modelling concept, 2D seismic profile and well data (i.e. logs and reports from four drilled wells) were integrated into a 3D structural model of the basin. Four source rock intervals (three from the Early Cretaceous stages namely; Hauterivian, Barremian, Aptian and one from the Late Cretaceous Turonian stage) were incorporated into the 3D model for evaluating source rock maturation and petroleum generation potential of the F-O Gas Field. Additionally, measured present-day temperature, vitrinite reflectance, source potential data, basin burial and thermal history and timing of source rock maturation, petroleum generation and expulsion were forwardly simulated using a 3D basin modelling technique. At present-day, Turonian source rock is mainly in early oil (0.55-0.7% VRo) window, while the Aptian and Barremian source rocks are in the main oil (0.7-1.0% VRo) window, and the Hauterivian source rock is mainly in the main oil (0.7-1.0% VRo) to late oil (1.0-1.3% VRo) window. In the entire four source rock intervals the northern domain of the modelled area show low transformation, indicated by low maturity values that are attributable to less overburden thickness. Petroleum generation begins in later part of Early Cretaceous, corresponding to high heat flow and rapid subsidence/ sedimentation rates. The Barremian and Aptian source rocks are the main petroleum generators, and both shows very high expulsion efficiencies. The modelling results however indicate that the younger Aptian source rock could be regarded as the best source rock out of the four modelled source rocks in the F-O field due to its quantity (i.e. highest TOC of 3%), quality (Type II with HI values of 400) and highest remaining potential. At present-day, ~1209 Mtons of hydrocarbons were cumulatively generated and peak generation occurred at ~43 Ma with over 581 Mtons generated. Finally, the results of this study can directly be applied for play to prospect risk analysis of the F-O gas field.

A Bacia de Santos é uma das principais bacias brasileiras para exploração e produção de hidrocarbonetos, e vem recebendo grandes investimentos em pesquisa nos últimos anos. O estudo das rochas geradoras serve como importante ferramenta para o estudo de modelos de geração, explusão e migração de hidrocarbonetos e na identificação de sistemas petrolíferos. O principal objetivo deste trabalho é a identificação de intervalos e áreas com maior potential para a geração de hidrocarbonetos dentro do pacote sedimentar estudado (Cretáceo-Terciário). As amostras de calha de 6 poços exploratórios, obtidas junto à Agência Nacional de Petróleo, Gás Natural e Biocombustíveis (ANP), foram analisadas através da geoquímica orgânica (Carbono Orgânico Total (COT), Pirólise Rock Eval e análise de Biomarcadores) e da petrologia orgânica (Reflectância da Vitrinita e Palinofácies) e foram interpretadas juntamente com os resultados do estudo de outros 10 poços exploratórios, obtidos pela Geochemical Solutions International cedidos para este trabalho. Esses 16 poços formam um perfil strike SW-NE que recobre praticamente toda a extensão da bacia. Amostras das formações Marambaia, Juréia, Santos, Itajaí-Açu, Itanhaem, Guarujá e Florianópolis foram analisadas, apresentando resultados semelhantes para o tipo de matéria orgânica, sua origem e ambiente deposicional (querogênio tipo II e III, originado pela mistura de material de origem terrestre e marinha depositado em ambiente transicional levemente oxidante). Os perfis analisados identificaram dois intervalos de maior conteúdo de carbono orgânico, maturação e potencial de geração de petróleo, um entre 2500 e 3000 metros de profundidade, que pode estar relacionado a eventos transgressivos do Terciário, e outro entre 4000 a 5000 metros de profundidade, possivelmente relacionado a um importante evento transgressivo de caráter regional ocorrido durante o Turoniano. A matéria orgânica encontrada nos poços situados na região sudoeste do perfil foi a que apresentou as melhores condições para a geração de hidrocarbonetos, tornando-se mais empobrecida na direção nordeste. Com base nos resultados geoquímicos e petrográficos obtidos, a matéria orgânica presente na Formação Itajaí-Açu possui o melhor potencial para geração de hidrocarbonetos, principalmente na porção basal do intervalo, na região sudoeste da bacia. / The Santos Basin is one of the main Brazilian sedimentary basin for hydrocarbon exploration and production and has been the focus of major geological research on hydrocarbon occurrences in recent years. Source rock studies are important tools for construction of hydrocarbon generation, expulsion and migration models of the basin and for identifying petroleum systems. The main objective of the present study is to identify areas and intervals with hydrocarbon generation potential inside the sedimentary sequence studied (Cretaceous-Tertiary). Cutting samples from 6 petroleum exploration wells obtained from the National Agency of Petroleum, Natural Gas and Biofuels (ANP) were analysed by organic geochemical methods (Total Organic Carbon (TOC), Rock Eval Pyrolysis and Biomarkers analysis) and organic petrography (Vitrinite Reflectance and Palynofacies) and were interpreted together with results from organic geochemical studies on samples from 10 addictional petroleum exploratory wells obtained from Geochemical Solution International (GSI), provided for this study. These 16 wells form a SW-NE strike section, that covers the basin almost completely in this direction. The samples from Marambaia, Juréia, Santos, Itajaí-Açu, Itanhaem, Guarujá and Florianópolis formations show similar results in regard to organic matter type, its origin and depositional paleoenvironment (type II-III kerogen, indicating a contribution of terrestrial and marine material, deposited in a transitional and slightly oxic environment). The stratigraphic profiles analysed identify two intervals with relatively high organic matter content, maturation and hydrocarbon generation potential, one between 2500 and 3000 meters depth, perhaps related to a Tertiary transgressive event and the other one between 4000 and 5000 meters depth, possibly related to an important regional transgressive event, which occurred during the Turonian. The organic matter encountered in the well samples located in the southwest of the SW-NE section has the best potential for hydrocarbon generation, whereas the organic matter of well samples located in the northwest direction has less potential to form hydrocarbons. Based on the results of the present study, the organic matter present in the Itajaí-Açu Formation has the best potential for hydrocarbon generation, in particular in the basal part of the formation in the southwest region of the basin.

A Bacia de Santos é uma das principais bacias brasileiras para exploração e produção de hidrocarbonetos, e vem recebendo grandes investimentos em pesquisa nos últimos anos. O estudo das rochas geradoras serve como importante ferramenta para o estudo de modelos de geração, explusão e migração de hidrocarbonetos e na identificação de sistemas petrolíferos. O principal objetivo deste trabalho é a identificação de intervalos e áreas com maior potential para a geração de hidrocarbonetos dentro do pacote sedimentar estudado (Cretáceo-Terciário). As amostras de calha de 6 poços exploratórios, obtidas junto à Agência Nacional de Petróleo, Gás Natural e Biocombustíveis (ANP), foram analisadas através da geoquímica orgânica (Carbono Orgânico Total (COT), Pirólise Rock Eval e análise de Biomarcadores) e da petrologia orgânica (Reflectância da Vitrinita e Palinofácies) e foram interpretadas juntamente com os resultados do estudo de outros 10 poços exploratórios, obtidos pela Geochemical Solutions International cedidos para este trabalho. Esses 16 poços formam um perfil strike SW-NE que recobre praticamente toda a extensão da bacia. Amostras das formações Marambaia, Juréia, Santos, Itajaí-Açu, Itanhaem, Guarujá e Florianópolis foram analisadas, apresentando resultados semelhantes para o tipo de matéria orgânica, sua origem e ambiente deposicional (querogênio tipo II e III, originado pela mistura de material de origem terrestre e marinha depositado em ambiente transicional levemente oxidante). Os perfis analisados identificaram dois intervalos de maior conteúdo de carbono orgânico, maturação e potencial de geração de petróleo, um entre 2500 e 3000 metros de profundidade, que pode estar relacionado a eventos transgressivos do Terciário, e outro entre 4000 a 5000 metros de profundidade, possivelmente relacionado a um importante evento transgressivo de caráter regional ocorrido durante o Turoniano. A matéria orgânica encontrada nos poços situados na região sudoeste do perfil foi a que apresentou as melhores condições para a geração de hidrocarbonetos, tornando-se mais empobrecida na direção nordeste. Com base nos resultados geoquímicos e petrográficos obtidos, a matéria orgânica presente na Formação Itajaí-Açu possui o melhor potencial para geração de hidrocarbonetos, principalmente na porção basal do intervalo, na região sudoeste da bacia. / The Santos Basin is one of the main Brazilian sedimentary basin for hydrocarbon exploration and production and has been the focus of major geological research on hydrocarbon occurrences in recent years. Source rock studies are important tools for construction of hydrocarbon generation, expulsion and migration models of the basin and for identifying petroleum systems. The main objective of the present study is to identify areas and intervals with hydrocarbon generation potential inside the sedimentary sequence studied (Cretaceous-Tertiary). Cutting samples from 6 petroleum exploration wells obtained from the National Agency of Petroleum, Natural Gas and Biofuels (ANP) were analysed by organic geochemical methods (Total Organic Carbon (TOC), Rock Eval Pyrolysis and Biomarkers analysis) and organic petrography (Vitrinite Reflectance and Palynofacies) and were interpreted together with results from organic geochemical studies on samples from 10 addictional petroleum exploratory wells obtained from Geochemical Solution International (GSI), provided for this study. These 16 wells form a SW-NE strike section, that covers the basin almost completely in this direction. The samples from Marambaia, Juréia, Santos, Itajaí-Açu, Itanhaem, Guarujá and Florianópolis formations show similar results in regard to organic matter type, its origin and depositional paleoenvironment (type II-III kerogen, indicating a contribution of terrestrial and marine material, deposited in a transitional and slightly oxic environment). The stratigraphic profiles analysed identify two intervals with relatively high organic matter content, maturation and hydrocarbon generation potential, one between 2500 and 3000 meters depth, perhaps related to a Tertiary transgressive event and the other one between 4000 and 5000 meters depth, possibly related to an important regional transgressive event, which occurred during the Turonian. The organic matter encountered in the well samples located in the southwest of the SW-NE section has the best potential for hydrocarbon generation, whereas the organic matter of well samples located in the northwest direction has less potential to form hydrocarbons. Based on the results of the present study, the organic matter present in the Itajaí-Açu Formation has the best potential for hydrocarbon generation, in particular in the basal part of the formation in the southwest region of the basin.

A Bacia de Santos é uma das principais bacias brasileiras para exploração e produção de hidrocarbonetos, e vem recebendo grandes investimentos em pesquisa nos últimos anos. O estudo das rochas geradoras serve como importante ferramenta para o estudo de modelos de geração, explusão e migração de hidrocarbonetos e na identificação de sistemas petrolíferos. O principal objetivo deste trabalho é a identificação de intervalos e áreas com maior potential para a geração de hidrocarbonetos dentro do pacote sedimentar estudado (Cretáceo-Terciário). As amostras de calha de 6 poços exploratórios, obtidas junto à Agência Nacional de Petróleo, Gás Natural e Biocombustíveis (ANP), foram analisadas através da geoquímica orgânica (Carbono Orgânico Total (COT), Pirólise Rock Eval e análise de Biomarcadores) e da petrologia orgânica (Reflectância da Vitrinita e Palinofácies) e foram interpretadas juntamente com os resultados do estudo de outros 10 poços exploratórios, obtidos pela Geochemical Solutions International cedidos para este trabalho. Esses 16 poços formam um perfil strike SW-NE que recobre praticamente toda a extensão da bacia. Amostras das formações Marambaia, Juréia, Santos, Itajaí-Açu, Itanhaem, Guarujá e Florianópolis foram analisadas, apresentando resultados semelhantes para o tipo de matéria orgânica, sua origem e ambiente deposicional (querogênio tipo II e III, originado pela mistura de material de origem terrestre e marinha depositado em ambiente transicional levemente oxidante). Os perfis analisados identificaram dois intervalos de maior conteúdo de carbono orgânico, maturação e potencial de geração de petróleo, um entre 2500 e 3000 metros de profundidade, que pode estar relacionado a eventos transgressivos do Terciário, e outro entre 4000 a 5000 metros de profundidade, possivelmente relacionado a um importante evento transgressivo de caráter regional ocorrido durante o Turoniano. A matéria orgânica encontrada nos poços situados na região sudoeste do perfil foi a que apresentou as melhores condições para a geração de hidrocarbonetos, tornando-se mais empobrecida na direção nordeste. Com base nos resultados geoquímicos e petrográficos obtidos, a matéria orgânica presente na Formação Itajaí-Açu possui o melhor potencial para geração de hidrocarbonetos, principalmente na porção basal do intervalo, na região sudoeste da bacia. / The Santos Basin is one of the main Brazilian sedimentary basin for hydrocarbon exploration and production and has been the focus of major geological research on hydrocarbon occurrences in recent years. Source rock studies are important tools for construction of hydrocarbon generation, expulsion and migration models of the basin and for identifying petroleum systems. The main objective of the present study is to identify areas and intervals with hydrocarbon generation potential inside the sedimentary sequence studied (Cretaceous-Tertiary). Cutting samples from 6 petroleum exploration wells obtained from the National Agency of Petroleum, Natural Gas and Biofuels (ANP) were analysed by organic geochemical methods (Total Organic Carbon (TOC), Rock Eval Pyrolysis and Biomarkers analysis) and organic petrography (Vitrinite Reflectance and Palynofacies) and were interpreted together with results from organic geochemical studies on samples from 10 addictional petroleum exploratory wells obtained from Geochemical Solution International (GSI), provided for this study. These 16 wells form a SW-NE strike section, that covers the basin almost completely in this direction. The samples from Marambaia, Juréia, Santos, Itajaí-Açu, Itanhaem, Guarujá and Florianópolis formations show similar results in regard to organic matter type, its origin and depositional paleoenvironment (type II-III kerogen, indicating a contribution of terrestrial and marine material, deposited in a transitional and slightly oxic environment). The stratigraphic profiles analysed identify two intervals with relatively high organic matter content, maturation and hydrocarbon generation potential, one between 2500 and 3000 meters depth, perhaps related to a Tertiary transgressive event and the other one between 4000 and 5000 meters depth, possibly related to an important regional transgressive event, which occurred during the Turonian. The organic matter encountered in the well samples located in the southwest of the SW-NE section has the best potential for hydrocarbon generation, whereas the organic matter of well samples located in the northwest direction has less potential to form hydrocarbons. Based on the results of the present study, the organic matter present in the Itajaí-Açu Formation has the best potential for hydrocarbon generation, in particular in the basal part of the formation in the southwest region of the basin.

L'étude des surpressions de fluide et de fracturation hydraulique des roches mères peut nous renseigner sur les mécanismes de génération qui en sont à l'origine. Ces dernières années, l'intérêt pour ces phénomènes s'est largement accru, notamment sous l'influence des sociétés pétrolières qui exploitent les ressources non-conventionnelles au cœur des problèmes énergétiques actuels. Dans ce travail de thèse, nous avons choisi deux approches différentes pour l'étude de ces mécanismes : (1) des exemples de cas géologiques naturels, et (2) le développement de la modélisation analogique. Ainsi, nous montrons que ces phénomènes sont très répandus au sein des bassins sédimentaires et que leurs manifestations s'expriment notamment par la génération de veines fibreuses parallèles à la stratification de la roche (beef), mais également par la formation de veines d'hydrocarbures solides (bitume). Nous démontrons également que les surpressions de fluides peuvent profondément changer le style de déformation d'un bassin sédimentaire par la génération de niveaux de décollement localisés au sein même des roches mères. Enfin, à l'aide de la modélisation analogique, nous avons pu identifier les mécanismes à l'origine des surpressions de fluide et de la fracturation hydraulique. En effet, lors de la génération d'hydrocarbures la transformation de solide à liquide de la matière organique conduit à la compaction chimique des sédiments. Par un mécanisme de transfert de charge lors de ce processus, ainsi que par l'accroissement de volume associé, des surpressions de fluides se développent et atteignent des pressions lithostatiques, capables de fracturer hydrauliquement les roches. / The study of fluid overpressures and hydraulic fracturing in source rocks can help us to understand the mechanisms, which are responsable for these phenomena. During the last few years, the interest in such processes has highly grown, especially through the influence of petroleum companies, which extract hydrocarbons from unconventional reservoirs. In this work, we have chosen to develop two different approaches for the study of these mechanisms: (1) field studies and (2) physical modelling. Thereby, we show that fluid overpressures and hydraulic fracturing are common in sedimentary basins worldwide. Bedding-parallel fibrous veins (beef) and solid hydrocarbon veins (bitumen) are the resulting structures. We also show that fluid overpressures can highly affect the deformation style in sedimentary basins, especially by causing thrust-detachments within source rocks. By the using of a new physcial modelling technique, we have identified the mechanisms, which are responsible for fluid overpressures and hydraulic fracturing. Indeed, during hydrocarbon generation, the solid organic matter becomes liquid, which leads to chemical compaction of the sediment. By a mechanism of load transfer, fluid overpressures rise to lithostatic values. However, volume changes also contribute, and are able to induce hydraulic fractures in the rocks.