Patent ID: 6064210
Filing Date: 2000-05-16
Classification: G01V

Abstract:
A resistivity logging system for use in measurement while drilling operations wherein the logging system is located in a down-hole assembly near a drill bit while a well is being drilled, the logging system comprising:a drill collar having a selected length;a transmitter sub connected to one end of the drill collar, the transmitter subhaving an insulating layer that electrically isolates a first portion of the transmitter sub from a second portion of the transmitter sub, wherein the first portion of the transmitter sub includes a first conductive material on a first inner annular surface of the first portion, and the second portion of the transmitter sub includes a second conductive material disposed on a second inner annular surface of the second portion;a receiver sub connected to a second end of the drill collar, the receiver subincluding at least one receiver electrode disposed over a selected portion of an outer annular surface of the receiver sub and at least one receiver electrode contact disposed on a selected portion of an inner annular surface of the receiver sub, the at least one receiver electrode coupled to the at least one receiver electrode contact via a conductive material disposed in the receiver sub, the conductive material being surrounded with insulating material;an instrument cartridge having a conductive body positionable within the drillcollar and subs, the cartridge including:at least a first electrical contact forconductively coupling with the conductive material disposed on the first inner annular surface of the transmitter sub;at least a second electrical contact for conductively coupling with the conductive material disposed on the second inner annular surface of the transmitter sub;at least a third electrical contact for conductivelycoupling with the at least one receiver electrode contact;at least a fourth electrical contact for conductivelycoupling with a portion of the inner annular surface of the receiver sub that is independent of the conductive material and the insulating material; andcurrent injection circuitry connected to inject current into the formationthrough the first electrical contact and current sensing circuitry connected to sense the current returned through the third electrical contact.