Banca de QUALIFICAÇÃO: REBECA SEABRA DE LIMA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : REBECA SEABRA DE LIMA
DATA : 08/12/2016
HORA: 09:00
LOCAL: Auditório do DG
TÍTULO:

GPR-DIGITAL IMAGING AND MODELING IN MICROBIALITES FROM FAZENDA ARRECIFE, CHAPADA DIAMANTINA (BA), NE BRAZIL

PALAVRAS-CHAVES:

Digital imaging, GPR, Microbialites

PÁGINAS: 22
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

GPR-digital imaging system allows the three-dimensional characterization of outcrops analogous to petroleum reservoirs. In carbonate rock systems it provides "vertical sections" through the studied formation and an insight to their internal geometry and, when georeferenced, allows the elaboration of virtual 3D models. The present study is based on combined usage of  GPR system, gamma ray profiling, sedimentary petrography and chemical analysis (SEM/EDS and XRF), and offers new perspectives for 3D virtual imaging of the internal and external geometry of microbialites, especially when associated with advanced GPR processing attributes applied in seismic interpretations. There is almost complete lack of information dealing with the detailed imaging of microbialites, which are of great interest  to oil industry. Therefore this work is intended to fill this gap delivering new information on an analogue to pre-salt reservoir. The application of advanced attribute processing to  GPR sections is relevant to extract additional information from the conventionally processed radargrams. The “Instantaneous Amplitude” attribute showed promising results highlighting the boundary between the colony of microbialites (low amplitude) and the storm deposits (high amplitude). The “Energy” attribute presented a similar result to the “Instantaneous Amplitude” attribute, which provided a better visualization of the internal lamination of the columnar microbialites. The combinations Hilbert Trace/Energy and Hilbert Trace/Similarity displayed adequatly the contact between stromatolite and tempestite, besides the internal geometry of the microbialite. The columnar sections and gamma ray profiles acquisitions were essential for the identification of granulometric changes between the tempestites layers (grainstones), for the parameterization of the width of the microbialites columns, as well as for the identification of ferruginous/phosphate material that is responsible for high amplitudes of the electromagnetic waves observed in the intense reflectors along the GPR sections. Consequently, it was possible to differentiate between two signatures of the tempestites (finer and thicker grainstones) and three signatures for the microbialites (larger, medium and smaller microbialites). The chemical analysis with SEM/EDS and FRX  allowed to identify presence of a phosphate mineral (26.8% P) and sections with higher iron concentration (16.2% of Fe), possibly related to the postdepositional processes of weathering/oxidation. The latter was confirmed by the presence of an iron oxide/hydroxide identified during petrographic study in polished sections. The present study has shawn that the applied tools allowed the detailed imaging of the microbialites outcropping in Fazenda Arrecife, which can represent cells of heterogeneity (ducts or flow barriers) in carbonate reservoirs not detectable by the conventional seismic methodology

MEMBROS DA BANCA:
Externo à Instituição - ANTÔNIO JORGE CAMPOS MAGALHÃES - PETROBRAS
Interno - 1315614 - DAVID LOPES DE CASTRO
Presidente - 1161652 - FRANCISCO PINHEIRO LIMA FILHO