Karin Goldberg

Evolução complexa de um meio-gráben: seção rifte da Bacia de Campos baseada em análise sismoestratigráfica

The rift section in the Campos Basin, comprises the basal and median portions of the Lagoa Feia Group, and includes the main source rocks in the basin, as well as carbonate reservoir rocks. Interpretation and systematic mapping of 2D seismic lines across two main half-grabens, integrated with lithological well-log data, allowed the construction of a chronostratigraphic chart and an evolutionary model for the initial phase of this basin. Ten seismic stratigraphic units, with corresponding bounding surfaces, and three seismic facies were defined, representing the main lithological groups in the rift section: border fault deposits, fine grain-dominated re-sedimented deposits and coarse grain-dominated re-sedimented deposits. The Campos Basin stratigraphy was subdivided in tectonic systems tracts, which reflect its tectonostratigraphic evolution. The rift initiation systems tract presents a well distributed tectonic. The high tectonic activity systems tract is marked by the significant fault movement. Finally, the low tectonic activity systems tract is characterized by processes of fault restriction. Analysis of each evolutionary step led to a tectonostratigraphic model. Initially, the rift sediments were deposited in synformal depression with no border fault. With continuation of the rifting process, deformation was concentrated along main faults, which led to the development of two half-grabens structure with defined border faults and increasing tectonics. This phase was followed by a stage of incipient fault movement until the cessation of rifting. Basin filling was thus complex and interdependent in the different troughs during the development of the Campos Basin.

Análise sismoestratigráfica da seção rifte da Bacia de Santos, Brasil

The Santos Basin, despite its surmount significance due to the pre-salt reservoirs, has limited geological information well-logs, 3D seismic or good quality 2D seismic for the rift section. The present work aims at integrating seismic stratigraphic analysis and proposing a tectonic-stratigraphic evolution model for the rift section of the basin. Seismic stratigraphic analysis involved interpretation of reflectors, which is the base of seismic stratigraphic units identification and seismic facies characterization. The result was the definition of 16 seismic stratigraphic units, four seismic facies (including the sag ), and the development of chronostratigraphic charts of events adapted to the seismic context. Based on the adaptation of the stacking patterns to tectonic activity changes model, it was possible to delimit the rift initiation system tract, the high tectonic activity system tract, the low tectonic activity system tract and the post-rift, represented by the sag . The development of each tectonic system tract responded to variations in controlling factors of the lacustrine basin, interpreted as the relative balance between the rate changes in the accommodation space generated by tectonic and sediment supply influenced by climate.

Modelo deposicional do Membro Ipubi (Bacia do Araripe, nordeste do Brasil) a partir da caracterização faciológica, petrográfica e isotópica dos evaporitos

As rochas evaporiticas se destacam nos estudos sedimentologicos e estratigraficos por sua associacao com rochas geradoras de petroleo como rochas selantes e por seu significado paleoclimatico e paleoambiental. A caracterizacao faciologica e petrografica quantitativa permitiu a definicao das facies e habitos dos evaporitos do Membro Ipubi da Bacia do Araripe, coletados em afloramentos localizados principalmente na regiao de Araripina, Pernambuco. Tecnicas de difratometria de raios X (DRX) e microscopia eletronica de varredura (MEV) foram utilizadas com o intuito de complementar a analise dos aspectos composicionais e texturais dos constituintes. Os sulfatos dominantes sao gipsita e anidrita, localmente celestita. Foram identificadas macroscopicamente tres facies (Evaporito laminado, Evaporito macico e Evaporito fraturado) e microscopicamente treze habitos para os sulfatos. Dentre estes, os habitos e as texturas primarios sao anidrita nodular, gipsita palicada e chevron , estas duas ultimas constituindo a textura laminada. Os demais sulfatos foram precipitados em condicoes pos-deposicionais rasas. As analises isotopicas de S e O nos sulfatos forneceram valores de δ 34 S entre +10,27‰ e +17,99‰ e δ 18 O entre +7,72‰ e +13,30‰, caracterizando a composicao marinha da salmoura geradora dos depositos. Os resultados obtidos indicam que os evaporitos do Membro Ipubi foram depositados em contexto subaquoso (salinas) e intrasedimentar em um sabkha costeiro.

Reconhecimento e análise das fácies sísmicas nas sucessões rift das bacias de Campos e Santos

Apresentando reservatorios em aguas profundas, o pre-sal das bacias de Campos e Santos e um cenario com depositos heterogeneos e complexos, e assim traz novos desafios para a interpretacao sismica. O presente trabalho tem como objetivo a caracterizacao sismica do intervalo rifte (de idade Hauteriviano Superior ao Barremiano, imediatamente abaixo dos reservatorios pre- -sal) nas bacias de Campos e Santos com a utilizacao de dados de sismica 2D e dois perfis de pocos. Foram analisadas as texturas sismicas e com a integracao dos dados litologicos se definiu tres sismofacies correspondentes: Sismofacies 1 (deposito de falha de borda) – apresenta comportamento semelhante em ambas as bacias e com ocorrencia encaixada na falha de borda em uma zona ampla e bem definida; Sismofacies 2 (deposito de sedimentos finos) – amplamente identificada nas bacias de Campos e Santos e que grada lateralmente para a sismofacies 3; Sismofacies 3 (deposito de grainstones e rudstones ) – em ambas as bacias tem ocorrencia restrita e de ocorrencia erratica, tanto em zonas altas da margem flexural, quanto nas zonas profundas proximas do depocentro dos meio-grabens analisados.

Primary composition and diagenetic patterns of sandstones from Barra de Itiúba Formation in Atalaia High, Sergipe Sub-Basin

The petrologic analyses of 40 thin sections from two wells located in Atalaia High, offshore of Sergipe Sub-Basin, allowed the identification of primary composition and diagenetic patterns of Barra de Itiuba Formation. The original detrital compositions included arkoses, sublithic, and lithic sandstones. The main diagenetic processes observed were: compaction of metamorphic rock fragments and mud intraclasts, generating pseudomatrix; precipitation of quartz and feldspar overgrowths and outgrowths, cementation and grain replacement by kaolinite; dolomite and ferrous dolomite/ankerite; pyrite; iron oxides and hydroxides; and diagenetic titanium minerals, in addition to dissolution phases during eo-, meso- and telogenesis. The macroporosity in the two studied wells is primary intergranular, but there is secondary porosity due to dissolution of primary and diagenetic constituents, as well as fracture porosity. Thirteen reservoir petrofacies were defined and grouped into four reservoir petrofacies associations. They reflect the reservoir quality in microscale: good, medium and low-quality and non-reservoir. The good-quality is characterized by average total porosity greater than 15%, whereas the medium shows average total porosity greater than 7%. Low-quality presents average total porosity between 1 and 4%, and the non-reservoir has an average total porosity consistently less than 1%. Overall, the studied reservoirs consist on low-quality and non-reservoir rocks, which are intercalated with levels of medium- and good-quality. The loss of original porosity was mainly due to mechanical compaction (generating pseudomatrix), and cementation by kaolinite and dolomite. Preservation of primary porosity was favored by the presence of quartz overgrowths.