Multi-array laterolog tools and methods with split monitor electrodes

摘要

Multi-array laterolog tool systems and methods acquire a set of array measurements sufficient to provide laterolog tool measurements of differing array sizes. Such systems and method offer multiple depths of investigation while offering greater measurement stability in borehole environments having high resistivity contrasts. In at least some system embodiments, a wireline or LWD tool body has a center electrode positioned between multiple pairs of guard electrodes and a pair of return electrodes. At least some of the guard electrodes are positioned between component electrodes of associated split monitor electrodes that enable more accurate measurement of the guard electrode potential. The tool's electronics provide a current from the center electrode to the pair of return electrodes and currents from each pair of guard electrodes to the pair of return electrodes. Each of the currents may be distinguishable by frequency or distinguishable by some other means.

主权项

1. A resistivity logging system that comprises:
a tool body having:
a center electrode positioned between multiple pairs of guard electrodes, wherein said multiple pairs of guard electrodes are positioned between a pair of return electrodes on said tool body; andmultiple pairs of split monitor electrodes, each of said split monitor electrodes having two electrically-coupled component electrodes with an associated guard electrode therebetween; and electronics that provide a primary current from the center electrode to the pair of return electrodes and provide a respective guard current from each pair in said multiple pairs of guard electrodes to the pair of return electrodes, the electronics further operating to acquire a voltage measurement from each of said pairs of split monitor electrodes.