| 摘要 |
A well logging apparatus and technique for measuring formation resistivity is disclosed which provides advantages of borehole compensation without the requirement of having, for each transmitter to receiver pair spacing, an "equal and opposite" transmitter with the same spacing on the other side of the receiver pair. In one disclosed embodiment there are provided two transmitting antenna at equal and opposite spacing from the midpoint of the receiving antenna pair, and a third transmitting antenna at a different spacing from the midpoint of the receiving antenna pair, without the need for providing a fourth transmitting antenna to obtain the benefits of borehole compensation. This reduces the complexity and cost of adding additional depths of investigation to a logging tool, while retaining the advantages of borehole compensation. In another disclosed embodiment at least three transmitting antennas are provided with at least one of them on one side of the receiving antenna pair and at least two of them on the other side of the receiving antenna pair. In this embodiment, none of the spacings between respective transmitting antenna and the midpoint of the receiving antenna pair are the same.
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