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Milnes, Ellen

Nom
Milnes, Ellen
Affiliation principale
Email
Ellen.Milnes@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/145

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  • Publication
    Accès libre
    Fracture characterisation using geoelectric null-arrays
    Falco, Pierik
    ;
    Negro, François 
    ;
    Szalai, Sándor
    ;
    Milnes, Ellen 
    The term “geoelectric null-array” is used for direct current electrode configurations yielding a potential difference of zero above a homogeneous half-space. This paper presents a comparative study of the behaviour of three null-arrays, midpoint null-array (MAN), Wenner-γ null-array and Schlumberger null-array in response to a fracture, both in profiling and in azimuthal mode. The main objective is to determine which array(s) best localise fractures or best identify their orientation.
    Forward modelling of the three null-arrays revealed that the Wenner-γ and Schlumberger null-arrays localize vertical fractures the most accurately, whilst the midpoint null-array combined with the Schlumberger null-array allows accurate orientation of a fracture. Numerical analysis then served as a basis to interpret the field results. Field test measurements were carried out above a quarry in Les Breuleux (Switzerland) with the three null-arrays and classical arrays. The results were cross-validated with quarry-wall geological mapping. In real field circumstances, the Wenner-γ null-array proved to be the most efficient and accurate in localising fractures. The orientations of the fractures according to the numerical results were most efficiently determined with the midpoint null-array, whilst the Schlumberger null-array adds accuracy to the results. This study shows that geoelectrical null-arrays are more suitable than classical arrays for the characterization of fracture geometry.