Method and apparatus for improved current focusing in galvanic resistivity measurment tools for wireline and measurement-while-drilling applications

摘要

A galvanic resistivity tool with one or more measurement electrodes and guard electrodes, and one or more shielding electrodes. The potential difference between the measurement electrodes and the guard electrodes is controlled to minimize current flow between the measurement electrodes and the shielding electrodes. This provides improved focusing and avoids effects of contact impedance.