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Previous issue date: 2014-04-03 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Este estudo foi desenvolvido em uma ?rea localizada na plataforma externa da Bacia Potiguar, margem equatorial brasileira. A amostragem de sedimentos foi realizada em tr?s campanhas, em torno de um po?o explorat?rio, para comparar as propriedades dos sedimentos do fundo marinho, incluindo granulometria, composi??o, conte?do de carbonato e mat?ria org?nica, anterior a perfura??o do po?o, com amostras coletadas 3 e 12 meses ap?s a perfura??o. O planejamento amostral utilizou 16 esta??es localizadas em 4 radiais distantes 50 m, 100 m, 250 m e 500 m do po?o. Os sedimentos foram analisados nas camadas 0-2 cm e 0-10 cm. Os resultados mostraram que a cobertura sedimentar em torno do po?o era pobre a muito pobremente selecionada, com granulometria predominante na fra??o areia grossa com granulo e cascalho, seguida por cascalho e lama. O conte?do de carbonato de c?lcio foi maior que 96%, associado a sedimentos biocl?ticos, e o conte?do de mat?ria org?nica foi menor que 12%. Apenas pequenas varia??es sedimentol?gicas ocorreram na ?rea afetada pelas opera??es de perfura??o. A principal diferen?a foi observada em amostras da segunda campanha, em termos de uma mudan?a na distribui??o granulom?trica associada a um aumento no conte?do de sedimentos silicicl?sticos. Este impacto ocorreu nos sedimentos mais superficias (0-2 cm), no raio mais pr?ximo ao po?o (50 m), e poderia sugerir o efeito da perfura??o. Entretanto, os sedimentos coletados na campanha 3, um ano ap?s a perfura??o, voltaram a apresentar as mesmas caracter?sticas da primeira campanha. Estes resultados indicam que n?o houve varia??es sedimentol?gicas significantes devido a atividade de perfura??o, e que a din?mica oce?nica na ?rea de estudo foi forte o suficiente para recuperar as caracter?sticas originais do ambiente.
ABSTRACT
This study was developed in an area located on the outer shelf in the Potiguar Basin, Brazilian equatorial margin; this tropical shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system. Field sampling was carried out during 3 cruises surrounding a shallow-water exploratory well to compare sediment properties of the seafloor, including grain-size, texture, mineral composition, carbonate content, and organic matter, prior to drilling with samples obtained 3 and 12 months after drilling. The sample grid used had 16 stations located along 4 radials from 50 m the well up to a distance of 500 m. Sediments were analyzed in the first 0-2 cm, and 0-10 cm layers. The results show that sedimentary cover around the well is poor to very poorly sorted, with the particle size predominantly in the medium to coarse sand fraction, followed by gravel and mud. The content of calcium carbonate is greater than 96%, associated to bioclastic sediments, and the content of organic matter is less than 12%. Only minor sedimentological variations occured ?in the area affected by drilling operations. The most noticeable effects were observed during the second cruise, in terms of a change in grain size distribution associated to an increase in siliciclastic content, This impact occurred in the most surficial sediment (0-2 cm), in the radial closest to the well (50 m), and could suggest the effects of drilling. However, in the third cruise, one year after drilling, the sediments return to show the same characteristics as in the first cruise. These results show no significant sedimentological variations due to drilling activity, and indicate that ocean dynamics in this area was high enough to recover the environment original characteristics. / This study was developed in an area located on the outer shelf in the Potiguar Basin,
Brazilian equatorial margin; this tropical shelf represents a modern, highly dynamic mixed
carbonate-siliciclastic system. Field sampling was carried out during 3 cruises surrounding a
shallow-water exploratory well to compare sediment properties of the seafloor, including grainsize,
texture, mineral composition, carbonate content, and organic matter. Cruise 1 (C1) was
carried prior to drilling, while Cruise 2(C2) and 3 (C3) respectivelly 3 and 12 months after
drilling. The sample grid used had 16 stations located along 4 radials from 50 m the well up to a
distance of 500 m. Sediments were analyzed in the first 0-2 cm, and 0-10 cm layers. The results
show that sedimentary cover around the well is poor to very poorly sorted, with the particle size
predominantly in the medium to coarse sand fraction, followed by gravel and mud. The content
of calcium carbonate is greater than 96%, associated to bioclastic sediments, and the content of
organic matter is less than 12%. Only minor sedimentological variations occured in the area
affected by drilling operations. Mainly observed during the second cruise, in terms of a change
in grain size distribution associated to an increase in siliciclastic content, This impact occurred in
the most surficial sediment (0-2 cm), in the radial closest to the well (50 m), and could suggest
the effects of drilling. However, in the third cruise, one year after drilling, the sediments return to
show the same characteristics as in the first cruise. These results show no significant
sedimentological variations due to drilling activity, and indicate that ocean dynamics in this area
was high enough to recover the environment original characteristics.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/21055 |
| Date | 03 April 2014 |
| Creators | Souza, Claudete Rodrigues de |
| Contributors | 31481981404, Lima, Zuleide Maria Carvalho, 44366825449, Corr?a, Iran Carlos Stalliviere, 17741548034, Vital, Helenice |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM GEODIN?MICA E GEOF?SICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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