| 摘要 |
An apparatus for investigating the wall of a borehole in a geological formation, the apparatus comprising:-a pad ( 90 ) having an inside face and an outside face for pressing against the wall of the borehole;-a set of measurement electrodes ( 6 ) mounted on the outside face of the pad and means for measuring the potential difference between two measurement electrodes;-both a source electrode ( 4 ) adapted to inject current into the formation and a return electrode ( 5 ), the set of measurement electrodes being situated between the source electrode and the return electrode. The pad further comprises shielding means ( 17, 18 ) which are arranged between the source electrode and the measurement electrodes and between the measurement electrodes and the return electrode, said shielding means being flush with or almost flush with the outside face of the pad.
|
