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Master's Dissertation
DOI
10.11606/D.14.2019.tde-10092018-080732
Document
Author
Full name
André Campos Guaragna Kowalski
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2017
Supervisor
Committee
Mendonça, Carlos Alberto (President)
Kiang, Chang Hung
Pereira, Sueli Yoshinaga
Title in Portuguese
Análise da conectividade de fraturas em maciços cristalinos utilizando perfilagem geofísica e modelos de percolação
Keywords in Portuguese
Comprimento de fraturas
Conectividade de fraturas
Imageamento ótico
Perfilagem geofísica
Perfilagens elétricas
Teoria da Percolação
Testes de bombeamento.
Abstract in Portuguese
O principal objetivo deste trabalho foi avaliar um procedimento de campo para testar o comprimento mínimo que fraturas devem ter para construir uma rede de fluxo em escala de dezenas de metros ao longo de maciços cristalinos. O comprimento mínimo é determinado a partir do limite de percolação, definido por modelos baseados na Teoria da Percolação e a densidade de fraturas no poço, determinada pela perfilagem ótica. Para testar o valor de 3,9 metros que foi encontrado, foram realizados bombeamentos em dois poços próximos enquanto o nível estático era registrado no poço de observação. O método apresenta facilidades em termos de operação e para obter-se o número de fraturas que interceptam o poço, no entanto o registro do nível estático é afetado por fatores externos, como presença de efeitos de maré e variação da pressão atmosférica, e correções são necessárias para permitir identificar a interferência proveniente somente do bombeamento.
Title in English
Analysis of fracture connectivity in crystalline rocks using well logging and percolation models
Keywords in English
Electrical logging
Fracture connectivity
Fracture length
Geophysical well logging
Optical well logging
Percolation Theory
Pumping tests.
Abstract in English
The objective of this work is to develop a field procedure to determine a minimum characteristic length forming a connected fracture network in crystalline rocks. This minimum length is determined as a percolation threshold defined by models based on Percolation Theory and fracture density data determined from borehole imaging with well-logging probes. The characteristic length (3.9 meters) once estimated for a testing well was evaluated by monitoring its water head meanwhile nearby wells at different distances were pumped. The water head variation recorded in the testing well was disturbed by interfering effects associated to earth tides and atmospheric pressure, requiring further corrections to isolate effects induced by pumping. The results of these tests validate the percolation limit determined from logging data suggesting a rock mass with very low connectivity. The proposed test can be regarded as simple and easy to apply in many practical situations, for example when evaluating groundwater resources or geotechnical properties in fractured crystalline rocks.
 
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Publishing Date
2019-01-22
 
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