Baixe Petroleum Br Overveiw e outras Exercícios em PDF para Engenharia de Petróleo, somente na Docsity! Petroleum Systems of Brazil www.pgt.com.br Petroleum Systems of Brazil PGT - Petroleum Geoscience Technology www.pgt.com.br PSPGT www.pgt.com.br e Petroleum Systems of Brazil Petroleum Systems of Brazil www.pgt.com.br • Cenomanian/Turonian marine source system. This system is composed by marine anoxic shales and marls mostly of Cenomanian/Turonian age. As the previous system, even though found along most of the Brazilian Margin, such rocks account only for some oil and gas fields in the Santos, Espírito Santo Basin, and Sergipe-Alagoas basins. • Tertiary marine source system. This system is composed by marine deltaic shales (Eocene/Oligocene?) which account for the gas and light oil accumulations found in the Foz do Amazonas/Pará-Maranhão and Espírito Santo basins. Reservoir and Seal Rocks Eleven major reservoir/seal sequences ranging from the Devonian to the Miocene can be recognized in the Brazilian petroleum systems: • Devonian. This sequence comprises marine sandstone reservoirs sealed by marine shales and diamictites of the same age. So far, only several oil and gas shows, and a few hydrocarbon occurrences were found in this sequence in the Amazonas, Parnaíba, Paraná and Solimões basins. • Carboniferous. Such reservoirs occur throughout the Paleozoic basins, showing good to excelent porosity and permeability characteristics, being sealed by pelitic rocks in the Paraná and Parnaíba basins, and by evaporites (carbonate, anhydrite and halite) in the Amazonas and Solimões basins. Practically all the oil and gas reserves of the Solimões Basin were found within Carboniferous reservoirs. The ‘’pie’’ diagram to the left shows the distribution of petroleum reserves (oil equivalent in place) according to its source. Regarding the marginal basins, practically all the petroleum was generated by pre-salt source rocks (Neocomian and Barremian rifts, and Aptian marine source systems). The remarkable contribution (73%) of the Barremian rift source system is due to the huge volumes of petroleum of the Campos Basin. Petroleum Systems of Brazil www.pgt.com.br • Carboniferous/Permian. Glacial marine sandstones sealed by pelitic rocks and diabase sills represent this sequence, which is restricted to the Paraná Basin. • Permian. Marine deltaic sandstones, also restricted to the Paraná Basin, represent this sequence. • Jurassic. Such reservoirs are composed by fluvial sandstones of the pre-rift sequence in the northeastern Brazilian Margin basins. The superimposed lacustrine shales of the rift sequence provide the seal. Such reservoirs contain most of the petroleum of the Recôncavo Basin, some fields in the Sergipe-Alagoas Basin, and a small accumulation in the Camamu-Almada Basin. • Neocomian. Fluvial-deltaic and lacustrine turbiditic sandstones sealed by lacustrine shales represent this sequence. The most significant petroleum accumulations related to this reservoir sequence are located in the Recôncavo, Sergipe-Alagoas and Potiguar basins. • Barremian. Coquina limestones sealed by lacustrine shales represent this sequence. The most significant petroleum occurrences are located in the Campos Basin, where there are several fields with the coquinas as the main reservoir. • Aptian. This sequence consists of fluvial to alluvial sandstones and conglomerates, which are apparently related to the Aptian unconformity, sealed by shales and evaporites. The most representative occurrences of petroleum are found in the Sergipe-Alagoas and Potiguar basins, and secondarily in the Espírito Santo Basin. • Albian. This sequence is represented by shallow marine carbonates with remarkable porosity/permeability changes controlled by halokinesis. The most important petroleum accumulations within Albian reservoirs are located in the Santos, Campos and Espírito Santo basins. This sequence also includes fluvial sandstones sealed by shales, being the main reservoir sequence in the Potiguar Basin. • Late Cretaceous. Turbidite sandstone reservoirs sealed by marine shales occur throughout most of the Brazilian Margin. The distribution and reservoir quality of these reservoirs are mainly controlled by the halokinesis, presence of continental sediment source areas, sea-level changes, etc. This sequence contains huge volumes of petroleum in the Campos and in the Santos basins. • Tertiary. This sequence comprises the most prolific reservoirs of the Brazilian Margin, being generally represented by submarine turbidite fans sealed by marine shales. The Petroleum Systems of Brazil www.pgt.com.br distribution and reservoir quality of such fans are controlled by sea-level changes, sediment availability (source areas), presence of retrograding canyons, and contour currents. These reservoirs contain most of the oil and gas reserves of the Campos Basin, as well as other minor accumulations in other marginal basins, such as the Espírito Santo, Sergipe-Alagoas, Cumuruxatiba, etc. The ‘’pie’’ diagram to the left shows the distribution of petroleum reserves (oil equivalent in place) by the age of reservoir/ seal sequence. The noticeable dominance of the Late Cretaceous and Tertiary sequences reflects the huge volumes of petroleum found in the turbidites of the Campos Basin. Entrapment Mechanisms A large variety of entrapment styles occur in the described petroleum systems. In the Paleozoic interior sags most of the petroleum is pooled in structural traps, mainly along anticlines related to the upthrow blocks of large reverse faults. Petroleum accumulations are also found within small stratigraphic traps, generally represented by sandstone lenses enclosed in the pelitic deposits of the Devonian sequence. Along the Eastern Atlantic Margin, most of the petroleum found in the pre-rift and rift sequences (Jurassic to Aptian) is pooled within structural traps, generally in the upthrown blocks of normal faults. This is the case of several oil fields in the Sergipe-Alagoas, Recôncavo, Espírito Santo and Campos basins. In the post-rift sequence, the structural traps are essentially related to halokinesis. There is a plenty of structures related to the sliding of the Aptian salt layer and to the formation of salt domes and ridges that affected all the post-rift reservoir sequences, but mainly the Albian and the Late Cretaceous reservoirs. A significant part of the petroleum found in the Campos, Santos, and Espírito Santo basins is trapped in that type of structure. In spite of the great importance of the structural traps in the post-rift sequence, the deep-water giant oil accumulations