Jorge Figueiredo

Petrographic analyses of forty-five volcanic rock samples from seven wells in the Santos Basin were conducted to investigate lithofacies distribution, eruptive styles, and petroleum system implications from the Aptian Barra Velha Formation to the Turonian– Maastrichtian Itajaí-Açu Formation. Six lithofacies were identified, including coherent basaltic lava flows, autobreccias, peperites, and lithic, vitric, and crystal tuffs. Lava flows composed mainly of plagioclase and augite (± olivine), commonly displaying amygdales and secondary alteration to chlorite, zeolites, calcite, and palagonite, dominate the early pre-breakup intervals. Younger post-breakup units are characterized by abundant volcaniclastic deposits and intense palagonitisation. Integrated petrographic and stratigraphic data indicate a temporal transition from predominantly subaerial Hawaiian and Transitional volcanism during the rift and post-rift stages to subaqueous Surtseyanstyle hydromagmatic activity during the drift phase, strongly influencing reservoir heterogeneity, porosity evolution, and seal development within the basin.

Amazonian environments are being degraded by modern industrial and agricultural activities at a pace far above anything previously known, imperiling its vast biodiversity reserves and globally important ecosystem services. The most substantial threats come from regional deforestation, because of export market demands, and global climate change. The Amazon is currently perched to transition rapidly from a largely forested to a nonforested landscape. These changes are happening much too rapidly for Amazonian species, peoples, and ecosystems to respond adaptively. Policies to prevent the worst outcomes are known and must be enacted immediately. We now need political will and leadership to act on this information. To fail the Amazon is to fail the biosphere, and we fail to act at our peril.

En este capítulo exploramos la forma como estas características evolucionaron a lo largo de una historia de tres mil millones de años, y mostramos que los períodos de separación continental seguidos por la formación de montañas finalmente llevaron a la subdivisión característica de la Amazonía occidental y oriental, al tiempo que generaron una gran cantidad de yacimientos de minerales, reservas de petróleo y gas y acuíferos de agua dulce.

The main oil-producing reservoirs in Roncador field, located in the central Campos Basin-Brazil, are composed of sandy deposits interpreted as turbidites of Campanian to Maastrichtian age, deposited on the contemporary submarine continental slope. Three main grouping of sandy deposits (RO400, RO300, and RO200, from base to top), interpreted as the result of three third-order depositional sequences, comprise the whole sedimentary succession of the Upper Cretaceous Roncador’s reservoirs. RO200 is the uppermost sandy deposit grouping composed of RO210 and RO220. This work analyzed, based on some geophysical methods, the RO210. This reservoir is a channel complex composed of at least two individual channels (lower and upper) filled mainly by sandy turbidites. The channel complex direction is N-S, accompanied by the fault plain direction of the main growth fault that separated the field into high and low blocks. The lower individual channel is tectonically controlled by the growth fault and has its axis confined and parallel to the fault plane at its western border. To the east, it can be seen the channel margin and / or the extravasation deposits. The upper channel is not tectonically controlled and shows the character of an unconfined channel, which could be an unconfined deposit such as a turbiditic lobe.

This chapter explores how geodiversity evolved over three billion years of history. It shows that periods of continental breakup followed by mountain building ultimately led to the fundamental physiographic subdivisions of the Amazon, and a wealth of landscapes, soils, ore deposits, oil and gas reserves, and freshwater aquifers. Data on the Amazon’s geodiversity support a central theme of the environmental sciences, that the formation of most natural resources (like rare-earth ores, hydrocarbons, freshwater aquifers, and fertile soils) requires natural processes to operate undisturbed over immense periods of geological time and across broad spatial domains.

The understanding of petrophysical characteristics, such as porosity and permeability, is a target in the reservoir characterization task, and understanding the behavior of these parameters is paramount for the exploration of hydrocarbons. The focus of this work was the characterization of the Barra Velha Formation, in Sururu Field, from a qualitative integrated analysis of geophysical data from two exploratory wells and petrographic data, in order to verify how they are corroborative. By using porosity-related well logs, i.e., density, nuclear magnetic resonance, neutron, and sonic logs, three groups of electrofacies were generated, representing high, medium and low porosity rocks. Besides, the wells could be correlated by the recognition of three main intervals according to their electrofacies distribution. With the description of thin section images (photomicrography), thirteen groups of distinctive microfacies, i.e., floatstone, stromatolite, spherulite, laminite, grainstone / microcrystalline limestone and packstone, differing in texture and pore size, were identified within the three electrofacies, allowing inferences about environmental energy for the study area. Qualitative microfacies analyses corroborate the electrofacies interpretation regarding porosity characteristics of the rocks.Keywords: Barra Velha Formation; Santos Basin; electrofacies; petrophysics. Análise comparativa de dados petrográficos e de interpretação geológica de perfis geofísicos para caracterização dos reservatórios carbonáticos do Pré-sal no Campo de Sururu, Bacia de SantosRESUMO. O entendimento de características petrofísicas, como porosidade e permeabilidade, é alvo no processo de caracterização de reservatórios e entender o comportamento desses parâmetros é fundamental para a exploração de hidrocarbonetos. Este trabalho buscou caracterizar de forma qualitativa o principal intervalo reservatório do pré-sal, a Formação Barra Velha, no Campo de Sururu da Bacia de Santos, a partir da análise integrada de dados geofísicos de dois poços exploratórios e dados petrográficos. Através do uso de perfis geofísicos de dois poços, i.e., perfis de densidade, ressonância magnética, nêutron e sônico, foi possível a geração de três eletrofácies, que representam rochas de alta, média e baixa porosidade. Além disso, os poços puderam ser correlacionados através da identificação de três intervalos principais conforme a distribuição das eletrofácies. Através da descrição de imagens de lâminas petrográficas (fotomicrografias), treze grupos de microfácies distintas, i.e., floatstone, estromatolitos, esferulititos, laminitos, grainstone/carbonato microcristalino e packstone, diferindo em textura e tamanho de poro, foram reconhecidas dentro das três eletrofácies, possibilitando inferências sobre a energia do ambiente para a área de estudo. Por fim, a análise das microfácies corroboraram a interpretação das eletrofácies no que concerne as características de porosidade da rocha. Palavras-chave: Formação Barra Velha; Bacia de Santos; eletrofácies; petrofísica

The Ceará Plateau offshore Fortaleza holds some particular characteristics when compared to the other seamounts of the Brazilian Equatorial Margin (BEM). Not only it is the largest and the closest to the continent, it is also located at the boundary between the continental and the oceanic crusts, while all the others seamounts along the BEM are located on oceanic crust. Seismic imaging of the Ceará Plateau shows a “disorganized” interior, probably of volcanic origin, overlain by a series of horizontal seismic reflectors that can be interpreted as pelagic/hemipelagic sediments. As large uncertainties exist about the age of the initial formation of this seamount, three scenarios must be considered. If the age of the volcanic edifice is Coniacian (1), then the overlying pelagic/hemipelagic sedimentary succession can include an almost continuous record of the last ~90 Ma at the Equatorial Atlantic Ocean. In the case that the volcanic edifice is Eocene in age (2), the sedimentary sequence would still encompass the upper Paleogene and all the Neogene. There is also the possibility that the volcanic edifice was built during multiple magmatic events (3). In this case, it is likely that the sediments are interfingered with volcanic rocks at the edge of the structure. Although the age estimation (between Coniacian and Eocene) has an uncertainty of more than 40 Myr, the current interpretation is that it developed initially as a volcanic edifice, formed by a series of magmatic events that occurred between the Santonian and the Eocene. Since then, the topography has been leveled by pelagic/hemipelagic sedimentation. Whichever was the initial age, a continuous and constant sequence of sediments deposited onto the Ceará Plateau, at the same latitude, and thus under the same oceanographic conditions, for the last several tens of million years. This represents a unique opportunity to record a long-term history of the Atlantic Equatorial Margin.

This article presents the scientific rationale for an ambitious ICDP drilling project to continuously sample Late Cretaceous to modern sediment in four different sedimentary basins that transect the equatorial Amazon of Brazil, from the Andean foreland to the Atlantic Ocean. The goals of this project are to document the evolution of plant biodiversity in the Amazon forests and to relate biotic diversification to changes in the physical environment, including climate, tectonism, and the surface landscape. These goals require long sedimentary records from each of the major sedimentary basins across the heart of the Brazilian Amazon, which can only be obtained by drilling because of the scarcity of Cenozoic outcrops. The proposed drilling will provide the first long, nearly continuous regional records of the Cenozoic history of the forests, their plant diversity, and the associated changes in climate and environment. It also will address fundamental questions about landscape evolution, including the history of Andean uplift and erosion as recorded in Andean foreland basins and the development of west-to-east hydrologic continuity between the Andes, the Amazon lowlands, and the equatorial Atlantic. Because many modern rivers of the Amazon basin flow along the major axes of the old sedimentary basins, we plan to locate drill sites on the margin of large rivers and to access the targeted drill sites by navigation along these rivers.