| 摘要 |
A multi-mode resistivity tool for use in an LWD system includes an asymmetri c transmitter design with multiple transmitters (T1-T5) capable of generating EM signals at multiple depths of investigation. An array of at least three receivers (R1-R3) 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 multimode 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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