Banca de DEFESA: IURIANNE MONIK MEDEIROS CONTI

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : IURIANNE MONIK MEDEIROS CONTI
DATA : 23/07/2018
HORA: 08:30
LOCAL: Auditório do departamento de Geofísica
TÍTULO:

GPR image and petrophysical measurements of karstified carbonate rocks from the Salitre Formation, northern Bahia

PALAVRAS-CHAVES:

Karst; Carbonates; Fractures; Porosity; Dielectric Permittivity; GPR

PÁGINAS: 67
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

Three-dimensional distribution of karstic zones and estimated porosity were obtained in fractured carbonate units of the Salitre Formation (Brazil) from GPR data. Low-amplitude GPR zones could be associated with mineral dissolution halos that developed around fractures and bedding planes. GPR volumes show a 3D mazelike geometry of the vertical karstified carbonate zones, similar with the set of passages controlled by ~N-S and E-W oriented fracture system, observed on surface in unmanned aerial vehicle images. Measurements in core samples indicate that the local karstification modified the density, dielectric permittivity and porosity of the studied carbonate rocks. While the average density and relative dielectric permittivity decreased 2714 to 2713 kg/m3 and from 7.36 to 6.81, respectively, the average porosity slightly increased from 0.95% to 1.08%. These changes in the rock properties affect the EM impedance contrasts between carbonate bedding, causing loss of the reflected GPR signal. The correlation between dielectric permittivity and porosity could be analyzed using the complex refractive index model (CRIM), which uses EM velocity estimated from GPR data. The CRIM porosities are somewhat lower than porosities derived from core sample due to different measurement scales. However, the fact that porosity is slightly higher in the karstified carbonates was maintained. In addition, GPR amplitude and frequency instantaneous attributes were used to estimate spatial variability in porosity throughout the whole GPR data volume. The crossplot of these two GPR attributes show that karstified zones generally cluster in narrow ranges of instantaneous GPR amplitude and in broad range of instantaneous GPR frequency. Assuming empirical correlation between physical properties and GPR attributes two predicted porosity volumes were established for the karstified carbonates in the studied area.

MEMBROS DA BANCA:
Presidente - 1315614 - DAVID LOPES DE CASTRO
Externo ao Programa - 1675166 - JOSIBEL GOMES DE OLIVEIRA JUNIOR
Externo à Instituição - JOSÉ ANTONIO BARBOSA - UFPE