05235285 is referenced by 132 patents and cites 17 patents.

Apparatus is disclosed for determining the resistivity of formations surrounding an earth borehole. An electrically conductive metal body, such as a drill collar on a drill string, is movable through the borehole. A transmitting toroidal coil antenna is disposed on the body and is energized to induce a current which travels in a path that includes the body and the formations. An electrode is disposed on the body, and an electrical signal resulting from said current is measured at the electrode to obtain an indication of the resistivity of the formations. In a disclosed embodiment, one or more electrodes can be mounted on a blade that is mechanically coupled to the body.

Title
Well logging apparatus having toroidal induction antenna for measuring, while drilling, resistivity of earth formations
Application Number
7/786137
Publication Number
5235285
Application Date
October 31, 1991
Publication Date
August 10, 1993
Inventor
Martin Luling
Danbury
CT, US
Jacques Jundt
Missouri City
TX, US
Stephen D Bonner
Sugar Land
TX, US
Brian Clark
Missouri City
TX, US
Agent
John J Ryberg
Wayne I Kanak
Martin M Novack
Assignee
Schlumberger Technology Corporation
TX, US
IPC
G01V 3/26
G01V 3/18
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