FICUS, a new in-situ probe for resistivity measurements in unconsolidated marine sediments

Physical properties of shallow sediments measured at a particular site can not easily be extrapolated over a given profile. The number of samples requ ired to define sediment properties adequately can then become time-consumin g and expensive. Laboratory and in-situ experimentations have shown that el ectrical probing. provides a useful complementary technique to extrapolate results from cores. These experiments have pointed out the need for quantit ative, easily-transportable and fast resistivity measurements combining hig h vertical resolution with azimuthal resolution and full coverage, in the s hallow subsurface. A new prototype probe called FICUS (Formation Imaging an d Goring for Unconsolidated Sediments) has been developed To bridge this ga p. FICUS is designed ra provide in-situ high resolution electrical resistiv ity 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. Labora tory images agree with theoretical predictions from numerical modelling. Th e obtained cm-scale resolution could be used for petrophysical and sediment ary purposes. The probe may offer additional information about changes in p orosity and pore morphology caused by climatic cycles, since electrical res istivity is known to be especially sensitive to these changes. The probe co uld also allow to detect and map organic pollutants in the future.