Patent ID: 8174266

Claim:
An apparatus for obtaining a resistivity image of an earth formation, comprising: (a) a downhole assembly configured to be conveyed in a borehole penetrating the earth formation; (b) a plurality of measure electrodes on the downhole assembly, each of the plurality of electrodes having a different capacitance to a wall of the borehole, wherein a first one of the plurality of measure electrodes has a different extent in at least one of (I) a first direction substantially parallel to a longitudinal axis of the downhole assembly, and (II) a second direction substantially orthogonal to the longitudinal axis of the downhole assembly than an extent of a second of the plurality of measure electrodes in at least one of: (I) the first direction, and (II) the second direction; and (c) at least one processor configured to: process measurements made by each of the measure electrodes, including determining a first resistivity of the earth formation using one of (I) a current in the first measure electrode, or (II) a voltage of the first measure electrode, and determining a second resistivity of the earth formation using one of (I) a current in the second measure electrode, or (II) a voltage of the second measure electrode; and process a subset of the measurements substantially unaffected by the different capacitances to produce an image of the borehole wall.