Patent ID: 6191588
Filing Date: 2001-02-20
Classification: G01V

Abstract:
An apparatus for use in a borehole investigating tool which is movable through the borehole for investigating the wall of the borehole, said apparatus comprising:a) a non-conductive pad adapted to be pressed against the borehole wall;b) a matrix of voltage electrodes carried on said non-conductive pad and adapted to sense voltages at the borehole wall, said matrix of voltage electrodes comprising at least six electrodes including at least three equally spaced pairs, with each of a first group of three electrodes of said at least six electrodes being horizontally displaced relative to the others of said first group of three, and each electrode of a pair being vertically displaced relative to another electrode of said pair;c) a first current source electrode adapted to inject a current into the borehole wall; andd) a first current return electrode adapted to drain current from the borehole wall at a location spaced apart from said first current source electrode, said matrix of voltage electrodes being located between said first current source electrode and said first current return electrode.