Patent ID: 8629678
Filing Date: 2014-01-14
Classification: G01V

Abstract:
1. An apparatus configured to provide an image of a resistivity property of an earth formation, the apparatus comprising: a logging tool configured to be conveyed in a borehole having a conductive fluid therein; a plurality of measure electrodes on a pad of the logging tool configured to sense an electrical current in the earth formation, each of the plurality of measure electrodes being surrounded by an associated insulator that extends away from the pad of the logging tool limiting a vertical current path in the conductive fluid along the borehole between each of the electrodes and the earth formation, such that a gap exists between an outer face of the pad and a wall of the borehole, the gap extending vertically along the borehole to axial ends of the pad; at least one guard electrode encircling the plurality of measure electrodes; and at least one processor configured to provide an image of the resistivity property using the current sensed by at least one of the plurality of measure electrodes, wherein each associated insulator further comprises a spacer that maintains a separation between a body of the corresponding associated insulator and the wall of the borehole, such that the plurality of measure electrodes is in direct contact with a continuous body of the conductive fluid in direct contact with the guard electrode where and when the pad is urged against the wall of the borehole.