Co-located antennas for well logging

摘要

An antenna assembly comprises first and second antennas on a support 33, their magnetic dipole centres 56 being co-located and having different orientations, and a set of openings 53 on the support through which one of the antennas 51 is wound. The assembly may have three antennas in different or orthogonal directions and an insulator placed between the antennas. There is an independent claim for an antenna assembly comprising a plurality of antennas on a support, their magnetic dipole centres being co-located, one of the antennas being a wire wound on the support. A further independent claim is for a logging tool (Fig 9) comprising such an assembly and one other antenna assembly spaced apart longitudinally from it. The resistivity of a formation can be derived by signals detected and transmitted by such a logging tool.