Recognition and analysis of seismic facies in the rift successions of the Campos and Santos Basins

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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.A Bacia de Santos, apesar de uma das principais bacias atualmente no Brasil exploradas devido à importância do pré-sal, possui pouca informação geológica, como registros de poço, sísmica 3D e sísmica 2D de boa qualidade na seção rifte. O presente trabalho visa à integração da análise sismoestratigráfica e proposição de um modelo de evolução tectonoestratigráfica para a seção rifte da bacia. A análise sismoestratigráfica envolveu a interpretação dos refletores, que é a base da identificação das unidades sismoestratigráficas e a caracterização das sismofácies. Como resultado, foi obtida a definição de 16 unidades sismoestratigráficas e quatro sismofácies (incluindo o sag), e o desenvolvimento das cartas cronoestratigráficas de eventos adaptadas para o contexto sísmico. Com base no ajuste do modelo de padrões de empilhamento para mudanças na atividade tectônica, foram delimitados os tratos de sistemas tectônicos de início de rifte, de alta atividade tectônica, de baixa atividade tectônica e o pós-rifte, representado pelo sag. O desenvolvimento de cada um dos tratos respondeu a variações dos fatores controladores das bacias lacustres, interpretado como o balanço relativo entre as taxas de mudanças do espaço de acomodação gerado pela tectônica e o aporte sedimentar influenciado pelo clima

Arquitetura estratigráfica dos depósitos fluviais albianos da base da Formação São Mateus no norte da Bacia do Espírito Santo

The alluvial deposits from the São Mateus Formation (Albian of the Espírito Santo Basin) consist of important reservoirs. However, there are few studies detailing the stratigraphy of this stratigraphic range. Consequently, this paper presents a study at the high-resolution stratigraphic subdivision of the basal section consists predominantly of alluvial deposits. Against the difficulties presented for the stratigraphic correlation of these deposits, the strategy of correlation was the subdivide of the succession alluvial in stratigraphic cycles. This method is based on the variation in the ratio between the rates of creation of accommodation and supply sediment (A: S) that directly controls the degree of amalgamation of sandstone bodies of the fluvial channels. Therefore, six cycles were defined composed internally for systems tracts of high and low accommodation. These cycles reflect the structuring of the amalgamation disposition of the fluvial channels with the deposits external to the channels through the ratio between the accommodation rate (A) and the sedimentary influx rate (S) forming cycles.Os depósitos aluviais da Formação São Mateus (Albiano da Bacia do Espírito Santo, Brasil) consistem em importantes reservatórios. Entretanto, existem poucos trabalhos detalhando a estratigrafia deste intervalo estratigráfico. Em decorrência disso, este trabalho teve por objetivo estabelecer um fatiamento estratigráfico de alta resolução da seção basal desta unidade, a qual é constituída por depósitos fluviais. Diante das dificuldades apresentadas para a correlação estratigráfica desses depósitos, a estratégia de correlação utilizada foi a subdivisão da sucessão aluvial em ciclos estratigráficos. Este método se baseia na variação na razão entre as taxas de criação de acomodação e suprimento sedimentar (A:S) que diretamente controla o grau de amalgamação dos corpos arenosos de canais fluviais. Com isso, foram definidos seis ciclos compostos internamente por tratos de sistemas de alta e baixa acomodação. Esses ciclos refletem a  estruturação do arranjo da amalgamação dos canais fluviais com os depósitos externos aos canais através da razão entre a taxa de acomodação (A) e a taxa de influxo sedimentar (S) formando ciclos

Estratigrafia de Seqüências Aplicada à Caracterização de Aqüíferos: um Estudo de Caso na Área de Candiota, Rio Grande Do Sul

Detailed stratigraphic analysis of the Early Permian (Artinskian/Kungurian) succession of the intracratonic Paraná Basin in southernmost Brazil has been applied focusing stratigraphic characterization of potential aquifers. In the study area, the counties of Candiota and Hulha Negra, in the southwestern region of Rio Grande do Sul state, the sedimentary succession (Itararé, Rio Bonito and Palermo units) is interpreted to have been formed in a shallow, wave-dominated sea, originated mainly in a mixed (tide and wave) influenced estuary setting. Four main depositional systems have been recognized: alluvial fan, fluvial-dominated delta, lagoonal estuary and barrier/shoreface. The regional correlation of the lithofacies within the different depositional systems has led to a high-resolution stratigraphic framework, with three third-order depositional sequences (i.e., unconformity-bounded depositional packages formed during a complete cycle of falling and rising base level). The main sandbodies occur within sequence 2 which is formed by seven fouthorder parasequences, and at the base of the third sequence. Under the viewpoint of groundwater prospecting, the best sandbodies occur within parasequences 1,2 4 and 7. Based upon the stratigraphic characterization, optimal borehole locations are given, as well as estimatives on productive dephs and water volume.Detailed stratigraphic analysis of the Early Permian (Artinskian/Kungurian) succession of the intracratonic Paraná Basin in southernmost Brazil has been applied focusing stratigraphic characterization of potential aquifers. In the study area, the counties of Candiota and Hulha Negra, in the southwestern region of Rio Grande do Sul state, the sedimentary succession (Itararé, Rio Bonito and Palermo units) is interpreted to have been formed in a shallow, wave-dominated sea, originated mainly in a mixed (tide and wave) influenced estuary setting. Four main depositional systems have been recognized: alluvial fan, fluvial-dominated delta, lagoonal estuary and barrier/shoreface. The regional correlation of the lithofacies within the different depositional systems has led to a high-resolution stratigraphic framework, with three third-order depositional sequences (i.e., unconformity-bounded depositional packages formed during a complete cycle of falling and rising base level). The main sandbodies occur within sequence 2 which is formed by seven fouthorder parasequences, and at the base of the third sequence. Under the viewpoint of groundwater prospecting, the best sandbodies occur within parasequences 1,2 4 and 7. Based upon the stratigraphic characterization, optimal borehole locations are given, as well as estimatives on productive dephs and water volume

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.A seção rifte da Bacia de Campos é composta pela porção basal a intermediária do Grupo Lagoa Feia, e inclui a principal rocha geradora da bacia, e rochas reservatório carbonáticas. A interpretação e o mapeamento sistemático de linhas sísmicas 2D em uma área chave da bacia onde ocorrem dois meio-grábens, integradas com dados de perfis litológicos de poço, e a construção de uma carta cronoestratigráfica, permitiram elaborar um modelo evolutivo para a fase inicial da bacia. Assim, foram definidas dez unidades sismoestratigráficas, superfícies limítrofes chave e três sismofácies, que representam os principais grupos litológicos da seção rifte: depósitos de falha de borda, depósitos ressedimentados de grãos finos e depósitos ressedimentados de grãos grossos. A estratigrafia da Bacia de Campos foi subdividida em tratos de sistema tectônico, que refletem sua evolução tectonoestratigráfica. O trato de sistema de início de rifte apresenta tectônica bem distribuída. O trato de sistema de alta atividade tectônica é marcado pela significativa movimentação das falhas de borda; e o trato de sistemas de baixa atividade tectônica é caracterizado por um processo de fault restriction. A análise de cada etapa evolutiva levou à proposição de um modelo tectonoestratigráfico. Inicialmente os sedimentos sin-rifte foram depositados em uma depressão sinformal sem a presença de falhas de borda. Com o contínuo rifteamento e aumento da atividade tectônica, a deformação concentrou-se nas falhas principais, resultando na formação de dois meio-grábens bem estruturados com bordas de falha bem definidas. Essa fase foi seguida por uma fase de movimentação incipiente das falhas de borda até cessar o rifteamento, resultando em um preenchimento complexo e interdependente entre as diferentes calhas da bacia durante seu desenvolvimento

Complex evolution of a half-grapha rift section of the Campos Basin based on a seismostratigraphic analysis

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Seismic and structural characterization of a pre-salt rifted section: the Lagoa Feia Group, Campos Basin, offshore Brazil

The exploration of pre-salt offshore SE Brazil presents a multifaceted deep-water scenario that is bringing new challenges to seismic interpretation in offshore Brazilian exploration and production. Reservoirs in this domain are complex, heterogeneous with layered carbonates which makes accurate reservoir characterization very challenging. Our study here deals with the seismic characterization of the stratigraphy of a lacustrine section from the Lagoa Feia Group (Winter et al., 2007) in the Campos Basin, which extends over an area of 100,000 km2. By using an extensive 2D seismic dataset and two deep well logs and core information, we propose a seismic facies analysis and structural characterization of the Lagoa Feia group focused in the inner proximal domain of the Campos basin. Inferences from well core and seismic stratigraphy clearly suggest that the all Lagoa Feia group has a syn-rift depositional character. Different pre- syn- and post-rift seismic stratigraphic units, with corresponding bounding surfaces, are then defined. Based on their seismic character, four seismic facies representing the main lithological package in the rift section are recognized: border fault deposits; fine grain-dominated re-sedimented deposits; coarse grain-dominated carbonate rich re-sedimented deposits; and an intrusive wipe-out zone affecting all the pre-salt unit. Using some simplified kinematic restoration we show that some of the normal faults affecting the lower units of the Lagoa Feia could be interpreted as pre-rift structures sensu latu but also as pre-existing structures re-activated during the main passive margin rift activities. By proposing this seismic classification and interpretation across the pre salt Campos Basin units, this work represents an introductory step to a facies classification and structural interpretation applicable at regional level in the internal SE Brazil offshore area

Sequence stratigraphy applied to aquifer characterization: a case study in Candiota Area, RS, Brazil

Detailed stratigraphic analysis of the Early Permian (Artinskian/Kungurian) succession of the intracratonic Paraná Basin in southernmost Brazil has been applied focusing stratigraphic characterization of potential aquifers. In the study area, the counties of Candiota and Hulha Negra, in the southwestern region of Rio Grande do Sul state, the sedimentary succession (Itararé, Rio Bonito and Palermo units) is interpreted to have been formed in a shallow, wave-dominated sea, originated mainly in a mixed (tide and wave) influenced estuary setting. Four main depositional systems have been recognized: alluvial fan, fluvial-dominated delta, lagoonal estuary and barrier/shoreface. The regional correlation of the lithofacies within the different depositional systems has led to a high-resolution stratigraphic framework, with three third-order depositional sequences (i.e., unconformity-bounded depositional packages formed during a complete cycle of falling and rising base level). The main sandbodies occur within sequence 2 which is formed by seven fouthorder parasequences, and at the base of the third sequence. Under the viewpoint of groundwater prospecting, the best sandbodies occur within parasequences 1,2 4 and 7. Based upon the stratigraphic characterization, optimal borehole locations are given, as well as estimatives on productive dephs and water volume.Detailed stratigraphic analysis of the Early Permian (Artinskian/Kungurian) succession of the intracratonic Paraná Basin in southernmost Brazil has been applied focusing stratigraphic characterization of potential aquifers. In the study area, the counties of Candiota and Hulha Negra, in the southwestern region of Rio Grande do Sul state, the sedimentary succession (Itararé, Rio Bonito and Palermo units) is interpreted to have been formed in a shallow, wave-dominated sea, originated mainly in a mixed (tide and wave) influenced estuary setting. Four main depositional systems have been recognized: alluvial fan, fluvial-dominated delta, lagoonal estuary and barrier/shoreface. The regional correlation of the lithofacies within the different depositional systems has led to a high-resolution stratigraphic framework, with three third-order depositional sequences (i.e., unconformity-bounded depositional packages formed during a complete cycle of falling and rising base level). The main sandbodies occur within sequence 2 which is formed by seven fouthorder parasequences, and at the base of the third sequence. Under the viewpoint of groundwater prospecting, the best sandbodies occur within parasequences 1,2 4 and 7. Based upon the stratigraphic characterization, optimal borehole locations are given, as well as estimatives on productive dephs and water volume

High resolution stratigraphy of initial stages of rifting, Sergipe-Alagoas Basin, Brazil

ABSTRACT: The present work aims to characterize the Neo-Jurassic to Neocomian succession of the Sergipe-Alagoas Basin, located in northeast region of Brazil, in order to discover the influence of tectonics on sedimentation in detailed scale and thus separating this sedimentary succession in tectono-stratigraphic units. Fieldwork observations and stratigraphic sections analysis allowed subdividing this rift succession into three depositional units that indicate different paleogeographic contexts. Unit I, equivalent to the top of Serraria Formation, is characterized by braided fluvial channel deposits, with paleocurrent direction to SE; unit II, corresponding to the base of Feliz Deserto Formation, is composed of anastomosed fluvial channel and floodplain facies associations; and unit III, equivalent to the major part of Feliz Deserto Formation, is characterized by delta deposits with polymodal paleocurrent pattern. The changes of depositional system, as well as paleocurrent direction, suggest that the previously described units were deposited in different evolutionary stages of rifting. Units I and II represent the record of a wide and shallow basin associated with the first stage of rifting. Unit I is characterized by incipient extensional stress generating a wide synclinal depression, associated to the low rate of accommodation and low tectonic activity. These two parameters progressively increase in unit II. The paleocurrent direction of unit I indicates that the depocenter of this wide basin was located at SE of the studied area. No conclusion could be done on paleocurrent from unit II because of the low amount of measurements. Unit III suggests a second stage marked by a deeper basin context, with a high rate of accommodation space associated with the lateral connection of faults and individualization of the half-graben. The scattering in the paleocurrent direction in this unit indicates sedimentary influx coming from several sectors of the half-graben. The boundary between these two stages is marked by a flooding surface that indicates an extremely fast transition and suggests a radical change in geometric characteristics of the basin due to the increase of tectonic activity