| 摘要 |
A multi-mode resistivity tool for use in a logging-while-drilling(LWD) syste m includes an asymmetric transmitter design with multiple transmitters capable of generating electromagnetic (EM) signals at multiple depths of investigation. An array o f at least three receivers is positioned amongst a transmitter array to detect the EM signals after they have traversed the region in the vicinity of the borehole. In a first mode, two pairs of receivers combine with the asymmetrical transmitter array to produce a plurality of compensated resistivity measurements. In an alternative mode, one pair of receivers, consisting of a receiver from each of the previous pairs, combines with the array of transmitters to create a plurality of non-compensated measurements. This multi-mode capability enables the resistivity tool to operate successfully in a wide variety of drilling formations and under a broad scope of drilling conditions.
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