| 摘要 |
A borehole tool (10) for logging resistivity of geologic formations, having at least two inner transmitters (14, 16) surrounded by at least two outer receivers (18, 20). Each transmitter (14, 16) is sequentially excited, and measurements are taken at each of the receivers (18, 20). The phase differences between these received signals are determined, once for each transmitter(14, 16), and the two values are averaged to estimate the resistivity value of the surrounding formations. More than two receivers (18 , 20) can be used. An azimuthal receiver array (42, 43) is also used to identi fy boundary transitions.
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