FICUS,a new in-situ probe for resistivity measurements in unconsolidated marine sediments |
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| Authors: | Lauer-Leredde Christine Pezard Philippe A Dekeyser Ivan |
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| Institution: | (1) Laboratoire de Mesures en Forage, ODP-NEB, BP 72, 13545 Aix-en-Provence cedex 4, France;(2) Centre d Océanologie de Marseille, CNRS, Université de la Méditerranée, 13288 Marseille cedex 09, France |
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| Abstract: | Physical properties of shallow sediments measured at a particular site can not easily be extrapolated over a given profile. The number of samples required to define sediment properties adequately can then become time-consuming and expensive. Laboratory and in-situ experimentations have shown that electrical probing provides a useful complementary technique to extrapolate results from cores. These experiments have pointed out the need for quantitative, easily-transportable and fast resistivity measurements combining high vertical resolution with azimuthal resolution and full coverage, in the shallow subsurface. A new prototype probe called FICUS (Formation Imaging and Coring for Unconsolidated Sediments) has been developed to bridge this gap. FICUS is designed to provide in-situ high resolution electrical resistivity images of the upper few meters of shallow unconsolidated sediments.Laboratory experiments have been completed to test the feasibility of this technique to provide resistivity images of unconsolidated sediments. Laboratory images agree with theoretical predictions from numerical modelling. The obtained cm-scale resolution could be used for petrophysical and sedimentary purposes. The probe may offer additional information about changes in porosity and pore morphology caused by climatic cycles, since electrical resistivity is known to be especially sensitive to these changes. The probe could also allow to detect and map organic pollutants in the future. |
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| Keywords: | high-resolution imaging electrical resistivity unconsolidated sediments modelling porosity shallow probe |
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