| 摘要 |
A multi-mode resistivity tool for use in a logging-while-drilling (LWD) system includes an asymmetric transmitter design with multiple transmitters capable of generating electromagnetic (EM) signals at multiple depths of investigation. An array of 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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