Banca de QUALIFICAÇÃO: REBECA SEABRA DE LIMA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : REBECA SEABRA DE LIMA
DATA : 12/08/2019
HORA: 14:30
LOCAL: Auditório do CCET
TÍTULO:

The Conduit-Seal System in Carbonate Rocks from Salitre Formation Caves, Irecê Basin, Brazil

PALAVRAS-CHAVES:

Caves, Conduit-Seal, Carbonate, Analogous

PÁGINAS: 53
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

The caves’study presented in this paper covers different stages of development. The initial phase of the research refers to the characterization of the conduit-seal system heterogeneities through the elaboration of a tectonic-stratigraphic framework of the studied caves, Ioiô and Lapinha Cave. In the second stage will be interpreted the dissolution processes responsible for the formation of the main porosity associated with the ducts, through the interpretation of the diagenetic events found in this system. The third and final stage consist of an evaluation if, whether or not, the conduit-seal system identified in these caves may represent a potential analogous to actual reservoirs. In the latter case, it will be analyzed how these caves can contribute to the study of reservoir rocks and which inherent features of the system can be considered analogous to these rocks. This information is important for the prediction of reservoirs ocurrences in karstified carbonate rocks. The Ioiô and Lapinha caves are composed of neoproterozoic carbonate rocks from the Salitre Formation, comprised in the Irecê Basin, Northeast Brazil. The first data collected consisted in columnar sections obtained at some sites inside the caves.  LiDAR scenes contributed to stratigraphic profiles elaboration through galleries walls description. Thin sections of these layers were made, as well as plugs of the basal portions and the portions closest to the ceiling of the caves, in order to identify porosity and permeability values characteristic of these layers. Preliminary results shows that in the Ioiô Cave the base carbonates (essentially dolomitic) have higher porosity and permeability values compared to the rocks near the ceilings. Dolomites are interspersed with millimeter layers of silt that are thickening towards the top of the sections. The petrographic study shows that the silt levels are composed of a typically siliciclastic mineralogical assemblage (quartz, biotite, feldspar, etc.), but may eventually contain associated dolomitization, present in zones of intense stylolitization. Porosity and permeability data found in the rocks near the cave ceiling are practically null, although it is possible to observe, on a microscopic scale, even rare stylolite porosity, corresponding to the dissolution event resulting from the stylolitization process. In the basal dolomite, here called the conduit, the porosity is mainly vugular and fracture. The presence of opaque minerals (pyrite and / or limonite) shows the incidence of iron-enriched secondary fluid, which justifies the presence of ferrous calcite and dolomite. Lapinha Cave presents the same lithological pattern, although in the top of the cave the presence of silt is less expressive, which justifies the porosity and permeability values not being as low as in the Ioiô Cave. At Lapinha Cave there are the same features as Ioiô Cave, but mainly in dolomitic packages near the ceiling of the gallery. In the latter case in the ceiling portions, especially at the point where the vertical succession was built, the sealing layer does not occur, unlike the other cave. In the next stages of this research, chemical analyzes will be performed to better define the mineralogical framework, the diagenetic sequence and the dissolution processes associated with the formation of karst. Shallow geophysics tool (GPR) will be also used for subsurface imaging, contributing to the elaboration of a more detailed geological model. Other caves will be studied, such as the Paixão Cave, Torrinha Cave and / or Calixto Cave, in order to identify lithological, petrological and petrophysical patterns associated with the conduit-seal system presented in these caves

MEMBROS DA BANCA:
Presidente - 1161652 - FRANCISCO PINHEIRO LIMA FILHO
Interno - 350640 - FRANCISCO HILARIO REGO BEZERRA
Externa à Instituição - Augusto Sarreiro Auler
Externa à Instituição - JANE NOBRE LOPES - UFRJ