Patent ID: 9400339
Filing Date: 2016-07-26
CPC Classification: G01V

Claim Text:
1. An apparatus for measuring electrical properties of an underground formation surrounding a borehole, comprising: a downhole tool suitable for operating in the borehole; a sensor pad coupled to the downhole tool; a plurality of electrodes mounted on the sensor pad and configured to face a wall of the borehole, wherein the plurality of electrodes comprises one or more larger electrodes having a first surface area on a face of the sensor pad and one or more smaller electrodes having a second surface area on the face of the sensor pad, wherein the second surface area is smaller than the first surface area; and an insulating layer extending over at least a portion of the plurality of electrodes facing the wall of the borehole, wherein the insulating layer in front of the one or more larger electrodes comprises a greater thickness than the insulating layer in front of the one or more smaller electrodes.